Spring 2008

Spring 2008

$7 US

www. .org

protection automation and control magazine46

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The Guru:Shri Mata Prasadpage 60

COVER PAGE: SUBSTATION DETECTIVE, ILLUSTRATION BY Terry McCoy PAC.SPRING.2008

60

cont

ents

3

PAC World Photo Gallery presents Protection in Digital Art

Go to pages 8 and 68

4 editorial 10 letters

11 news The latest news from the world of electric power systems protection, automation and control

18 cover story On the challenges faced by protection engi-neers today and how to overcome them

27 IeC 61850 update The life cycle of an IEC standard and how itrelates to IEC 61850

28 lessons learnedSubstation "horror stories" - manufacturer's analysis and perspective on some events

34 blackout watchReview of recent blackouts or disturbances around the world

36 utilities challengesChallenges and opportunities faced by the utilities when using modern protection and control systems

38 fault locator Precise distance to fault locator with two-end phasor measurement transmitted via serial protection data interface

46 61850 engineeringReview on designing IEC 61850 systems for maintenance, retrofit and extension

53 legal issueClass action lawsuits - are they possible after a blackout occurs?

54 EMPT modeling The application of electromagnetic tran-sient programs (EMPT) for power system protection

60 the guru: interview Shri Mata Prasad shares with us the story of his life and his thoughts about our industry

70 history This is the second article on the develop-ments of distance protection

77 I think Do we really need Smart Grids? Marco Jans-sen shares his thoughts on that issue

79 industry reportsCIGRE B5 goals and activities, as well as an IEEE PSRC guide on breaker failure protec-tion are discussed

83 conference reportsReports on conferences in the United Kingdom and the United States

91 photos of the issueA selection of photos submitted by PAC World readers is presented

93 book review

94 hobbyBenton Vandiver III shares with us some of his BBQ experience and secrets

98 final thoughts

98 events calendar

38

PROTECTION, AUTOMATION & CONTROL WORLD SPRING 2008/VOLUME 04

94

8370

77

10

91

18

11

from

the

edit

orby Alex Apostolov

Com

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4

PAC.SPRING.2008

The work of a protection specialist in many ways is similar to what a detective needs to do. It actually goes beyond that, because while Sherlock Holmes needs just his magnifying glass and pipe to solve a crime that has already occurred, we need a very different set of tools not only to solve a system event after it happens, but also to design and configure the protection, automation and control system in a way that will prevent such an event.

Like detectives we first need to collect the evidence. This requires a trained eye that can recognize something significant that may look like garbage to everybody else. But a trained eye is not sufficient. Powerful tools can definitely help us to figure out not only what happened, but also when and where. If we keep the detective analogy in mind, this is like asking today’s investigators to use only a magnifying glass instead of DNA testing, microscopes, spectral analysis and other available tools.

Understanding when an event occurred is another important task in our detective work. Modern protection IEDs provide time stamping of different events based on relatively accurate time synchronization. However, we usually do not think about when the time-stamp was actually put on the event. For example, if the device senses the change of state of a breaker based on monitoring of its binary inputs, the enabling of filtering and

PAC World is your forum

the frequency of checking of the inputs may have a significant impact on the accuracy of the time stamp.

Fault locators are another very powerful tool that helps us answer the question of where a fault occurred. Here again we need to understand the limitations of single-ended fault location algorithms and the benefits of double-ended methods. The impact of mutual coupling and unbalanced configurations should be considered.

The task to prevent some system events from happening can also be achieved by using the twenty first century technology available to us. We already made the transition from electromechanical relays to microprocessor based mult ifunc t ional protec t ion, automation and control intelligent electronic devices. However, even though we have advanced programs for fault analysis and protection coordination, they are predominantly based on sequence components for modeling the generators, transformers and power lines. They were used for calculation of fault currents and voltages when the main tool available to us was a slide-rule.

The problem is that sequence components work well for a balanced system. But in real life most transmission lines are untransposed, with unsymmetrical configuration and running in parallel with other

lines with the same or different voltage. Modeling such systems with symmetrical components introduces errors that may lead to relay misoperation followed by local or wide area disturbance.

It is important to also understand that the model usually used is based on the sub-transient impedance of the generators. We know that this model is valid only during the first few cycles after a fault occurs in the system. So we need to be aware of what impact this may have on the coordination of protection elements that have longer time delays.

Modeling of the protection relay characteristics as generic mho or quadrilateral introduces another level of uncertainty in the performance of a protection device under real system conditions.

The use of electromagnetic t r a n s i e n t p r o g r a m s c a n significantly improve the accuracy of the analysis of possible fault condit ions in systems w ith different configurations. Accurate modeling not only of the distance characteristic, but also all other components of the dist ance protection function can bring the coordination and relay setting process to a different level.

I hope that the articles in this issue are going to trigger some reaction from you and start a process of change that will allow us to better design, configure and operate protection systems. It is clear that we can change the way we do things. As Leo Tolstoy said:

In this issue we continue our discussion of topics important to protection professionals. After discussing the concepts for protection of transmission lines around the world, now we are going to talk about electric power systems analysis from the point of view of protection.

Everyone thinks of changing

the world, but no one thinks

of changing himself.

cont

ribu

tors

6

PAC.SPRING.2008

Marco C. Janssen Marco C. Janssen graduated the Polytechnic in Arnhem, The Netherlands and further developed his professional skills through programs and training courses. He is President and Chief Commercial Officer of UTInnovation LLC – a company that provides consulting and training services in the areas of protection, control, substation automation and data acquisition, and support on the new international standard IEC 61850, advanced metering and power quality. He is a member of WG 10, 17, 18, and 19 of IEC TC57, the IEEE-PES and the UCA International Users Group. Marco coaches his son’s football team and enjoys watching science fiction movies as well as traveling, good food and wine.

Demetrios Tziouvaras was born in Monahiti, Grevena, Greece. He holds a M. Sc. in Electrical Engineering from Santa Clara University, CA, USA. He worked for 8 years with Pacific Gas

and Electric Co and joined the R&D Engineering Department of Schweitzer Engineering Laboratories, Inc. in 1998. Mr. Tziouvaras is a senior IEEE member and member of the PSR

Committee. He is a member of CIGRE and the convenor of CIGRE SC B5.15 on “Modern Distance Protection Functions and Applications.” He has taught many seminars and is the author of more than 35 conference papers, and three patents. He served as chairman of an

IEEE PSRC working group that developed an IEEE PES tutorial on “EMTP Applications to Power System Protection”. When he has free time on weekends he likes to cook some of his favorite Greek dishes, take care of the Tziouvara’s ranch near San Francisco, CA, go camping

and ride his two beautiful horses with his wife Diana. Mr. Tziouvaras is married and has a daughter and a son named Panagiota and Athanasios respectively.

Wolfgang Wimmer works for ABB Switzerland in Baden. He is Principle Engineer in the development of substation automation systems. He has a M. Sc. degree as well as a Ph.D. in Computer Science from the University of Hamburg. After some years developing Computer networks at the German Electron Synchroton DESY in Hamburg he changed to ABB for development of train control systems, later Network Control Systems. He has more than 20 years experience with development of substation automation systems. He is a member of IEC TC57 WG 19 and WG 10, and editor of IEC 61850-6. Wolfgang likes walking in the mountains as well as at rivers, reading popular books about biology, especially neuroscience, as well as science fiction and fantasy books.He also enjoys listening to country music.

Demetrios Tziouvaras

Ivan De Mesmaeker received M.Sc. Engineering Degree from the University of Brussels in 1968. He joined BBC (later ABB) in Baden, Switzerland in 1969. He was Project leader of the first steady-state distance protection of BBC and of the first numerical line protection, as well as test set equipment. He is currently Senior Technical Manager for Protection and

Control Systems. He was member of CIGRE Working Group 34-04 (1980-1986) and Swiss delegate in SC34 of CIGRE (till August 2000). He received the CIGRE Technical Committee Award in January 2001 and has been Chairman of Study Committee B5 of

CIGRE since 2002. He has authored and co-authored several professional papers.When not working, he enjoys skiing, hiking, camping and

editing of video films about holidays.

Ivan De Mesmaeker

Wolfgang Wimmer

Job

trac

k - E

xper

ien

ce -

Hob

by

Photography by Terry McCoy,HawkEye Communications,Houston, Texas.

GALLERY

PAC.SPRING.2008

Digital Art by Harmeet Kang

continued on page 68

Harmeet KangUK

Locus of a swing passing

harmlessly by a

moon-shaped like

distance characteristic

(load blinders cut out)

All is Well

Harmeet is a

protection design engineer

at AREVA T&D

Automation, Stafford, UK

who believes that

protection is not just

science, but

art as well

PAC.SPRING.2008

lett

ers

wh

at y

ou th

ink

10

PAC.SPRING.2008

protection. Make him feel that it is COOL

and let us know if it is working, so we can

use your experience.

I would like to see a section on Tips and

Tricks: how to test faster, how to do some­

thing easier, suggestions by vendors, etc.

Also a section on how to quickly calculate

settings in the field for commissioning

would be useful.

Luis Antonio Soto R., Mexico

PAC World: Dear Luis Antonio , we plan

to have an issue next year dedicated to

testing. However, we would like to encou­

rage our readers to share their knowledge

of the subjects mentioned in Luis’ e­mail.

In the article "A Pilot Protection system

Failure ­ An Investigation," Mr. Collin M.

Martin mentioned the term "FID rating" on

page 29 of the Winter 2008 issue. I've ne­

ver heard this term. What does it mean?

João Ricardo da Mata Soares de Souza, Brazil

PAC World: Dear Ricardo, the following is

the response we received from the author

of the article:

FID = Fault Interrupting Device. In this in­

stance FID is referring to circuit switchers

that are only rated to interrupt 20kA. De­

One Sunday morning I was surprised at

the book my son Thomas had chosen to

pick up while I was cleaning. I admit the

book fell over and I had to stand it back

the way he originally had it before I turned

on the camera, but the pose is identical to

his natural interest a few seconds before­

hand and he still seems intrigued. Maybe

there is hope for the industry ­ unless I tell

him that law or finance pays more!

Simon Richards, UK

PAC World: Dear Simon, yes, there is

hope. Please keep your son excited about

pending on the fault, the current could be

higher than the interrupting rating so they

are blocked from operating in these cases.

This adds some complexity/sensitivity to

the relay coordination because the line

relays must see these faults and operate

quickly.

Thanks for the wonderful magazine. Fi­

nally, a magazine that I feel like carrying

with me wherever I go. Keep up the good

work!

Amitava Maity

I found your magazine/web site very

interesting and useful. In order to inform

other specialists about it, an e­mail was

sent to hundreds of people who are active

in the Protection, Automation and

Control world. Your activities are very valu­

able and I want to thank everybody who

supports this idea.

Mehdi Gerivani, Iran

PAC World: Dear Mehdi , thank you for

spreading the word about PAC World.

Please also encourage your colleagues to

share their experiences through articles,

comments, photos and anything else they

think would be of interest.

PAC World (Email: editor@pacw.org)

8 Greenway Plaza, Suite 1510

Houston, TX 77046, USA

The PAC World magazine is published quarterly by PAC World. All rights

reserved. Reproduction in whole or in part of any material in this publication

is allowed.

Parent company: OMICRON electronics Corp. USA

address

Don't hesitate.

Tell us what you like

and what we can

do better. Share

your thoughts and

experiences.

pac world

Editor in chief: dr. Alexander Apostolov (USA)

Managing Editor: Izabela Bochenek (Poland)

Editors: Clare Duffy (Ireland), Caroline Fricks-Wood

Christoph Brunner (Switzerland)

Design Layout: Marek Knap (Poland)

Graphic Design: Terry McCoy (USA),

Iagoda Lazarova (USA), Dan-Andrei Serban (Romania)

Advisory Board: dr. Damir Novosel (USA),

prof. Peter Crossley (UK), prof. Paul Lee (Korea),

prof. Xinzhou Dong (China),

prof. Mohindar Sachdev (Canada),

Jorge Miguel Ordacgi Filho (Brazil),

Rodney Hughes (Australia),

Graeme Topham (South Africa)

11

PAC.SPRING.2008

industrytech+ news1

Virgin ia Tech engineer ing professors James Thorp and Arun Phadke are recipients of the 2008 Benjamin Franklin Medal in Electrical Engineering for their combined contributions of more than 60 years to the power industry.Specifically, they have collaborated on many advances that strengthen the electric utility industry’s ability to prevent power grid blackouts, or to make them less intense and easier to recover from. For this collaborative work, the Franklin Institute has now included Thorp and Phadke into its list of

the greatest men and women of science, engineering, and technology. Competition for the Benjamin Franklin Medals is international. Participants from seven fields of science are eligible: chemistry, computer and cognitive science, earth and environmental science, electrical engineering, l ife science, mechanical engineering and physics. In the past, Albert Einstein, Thomas Edison, Orville Wright, Marie and Pierre Curie and Jane Goodall have been among the recipients. “Professors Thorp and Phadke, both

members of the National Academy of Engineering, are considered to be preeminent trailblazers in their fields of electric power,” said Richard Benson, dean of Virginia Tech’s College of Engineering. “Their research has a direct impact on the daily lives of everyone around the world. In fact, both are also members of a prestigious Chinese funded research team directed to improve the protection and security of the worldwide, interconnected electric power grid.” For more information go to: http://www.fi.edu/franklinawards/

Franklin Institute Award

Virginia Tech

engineering

professors James

Thorp and Arun

Phadke , USA

indu

stry

new

syo

u c

an't

mis

s it

12

PAC.SPRING.2008

Toshiba continues the roll-out of its IEC 61850 product range, with its world-beating current differential protection GRL100 now supporting the global standard for substation communications. GRL100 follows the GRZ100 distance protection, GRT100 transformer protection and GBU100 bay controller, all of which have been certified IEC 61850 compliant by KEMA. Toshiba’s GRL100 is an advanced line differential protection relay which combines sub-cycle performance with a range of enhancements such as integrated distance protection, GPS synchronisation with sophisticated back-up modes, multi-phase r e c l o s i n g f o r double-circuit lines a n d I E C 6 1 8 5 0 capabilities.

Toshiba’s State-of-the-Art Line Differential Relay – Now with IEC 61850

2

4 GE Digital Energy's breakthrough in networking

The 2007 Vladimir Karapetoff Award was given to Stanley H. Horowitz, Consultant and Arun G. Phadke of Virginia Tech on March 19, 2008 at Hyatt Regency at Penn’s Landing, Philadelphia, PA. The award is given for their technical contributions to the field of power system protection and control.This major HKN recognition for career accomplish ment in the field of electrical and computer engineering dates

from 1922, when the Board of Governors established the award in honor of Vladimir Karapetoff, an IEEE Fellow and a prominent member of Eta Kappa Nu. The award is given annually to an electrical practitioner who is distinguished himself/herself through an invention, a development, or a discovery in the field of electro technology. Factors that are considered in bestowing the award include the impact and the scope of applicability

of the invention, develop ment, or discovery; its impact on the public welfare and standard of living, and/or global stability; and the effective lifetime of its impact.

Outstanding Technical Achievement

2007 Karapetoff Award3

GE Digital Energy unveils a breakthrough in networking hardware that can reduce up to 70% of your total communications costs with the introduction of their new Multilin UR Switch Module. A fully managed, embedded Ethernet switch for their flagship Universal Relay (UR), this advanced, 6-port Ethernet Switch eliminates the need for external, rack-mounted switches. More importantly, it significantly reduces the total costs associated with hardware, installation, wiring, and troubleshooting required for today’s traditional substation communication architectures. The Multilin UR Switch Module delivers full station management, monitoring, and control functionality with complete communications redundancy.

Stanley H. Horowitz

13

IEC 61850

PAC.SPRING.2008

A free demo version with some restricted functionality is available at: http://www.omicron.at/en/products/substation/iec-61850/iedscout/

Applications of Siemens SIPROTEC Relays have revolutionized the transfer scheme designs. Using only two basic feeder protection relays Siemens can realize for example a Fast Motor Bus Transfer Scheme per ANSI C50.41-2000. Motor Bus systems are critical loads which can not endure long separations from the power supply. In both industrial and utility power plant applications, the consequences of an unplanned motor bus outage can be costly, time consuming and dangerous. The load must be transferred to a redundant source. The speed

of this transfer is critical for the stress of the electrical system, the continuity of plant operations and the protection of the motors. The High-Speed Motor Bus Transfer Scheme is capable of providing both close and open transition transfers. Transfer schemes are realized for most applications per customer specifications. The whole system is delivered fully programmed, tested and ready for installation. Optionally incorporating IEC61850 communications makes implementation fast, secure and cost-effective.

AREVA T&D Automation launched MiCOM S1 Studio – a new integrated IED configuration and monitoring tool that will make users’ life easier by providing an intuitive and versatile interface with built-in file management facilities and IEC 61850 support. The MiCOM S1 Studio interface was designed with simplicity and customization in mind. It has a panel-based interface where elements are resizable, dockable, movable and removable. The software remembers your layout when you exit, so that the next time when you use it, you start where you finished. MiCOM S1 Studio has been developed with the various needs of different users in mind - protection and commiss ion ing engineers or system integrator, who want to configure devices offline in the office or work online communicating directly with devices in the substation.

New Configuration and Monitoring Tool

7

SIPROTEC Fast Bus Transfer scheme solution

OMICRON electronics released a new version of the IED Scout - an IEC 61850 tool that can be used both in the laboratory or in the field for testing, troubleshooting, c o m m i s s i o n i n g a n d I E D development. IED Scout allows the user to perform different tasks, such as :

extract the data model from an IED

check the extracted IED data model

create an SCL file

subscribe and monitor GOOSE messages

poll data receive reports

I n add i t i on to the ex i s t i n g capabi l it ies, the new version supports:

GOOSE Sniffer (capturing GOOSE messages online on the network)

Drag & Drop / Copy & Paste of discovered GOOSE information to the GOOSE Configuration Module

Improved user interface

IEC 61850 ToolA new version of the IED Scout !

5

6

indu

stry

new

syo

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14

PAC.SPRING.2008

Non-OperationalData Access

Terminal Block and Switch – All In One

DIN-rail or with screws, making it exceptionally versatile.

S e c u A c c e s s p e r f o r m s b o t h functions of a terminal block and switch, and therefore reduces wiring and panel space needs.

The terminal block/switch has a modular buildup and attaches to many wire terminal types (ring/spade/solid wire). Testing is easily

done by insert ing a testplug into the access point. Just like the Interface Test System, SAX features a finger-safe front and keyed entry system. C u r r e n t s h o r t i n g testp lugs p rov ide additional user safety.

With an internal resistance of only ca. 2mΩ, SAX is an ideal solution for the use with highly sensitive microprocessor relays.

8

9

Accessing breaker wear, fault records and oscillography from relays is now easier through the use of a set of software tools for the Orion Automation Platform. NovaTech's Orion Software Suite includes tools to:

Access relays remotely, through Orion Make Breaker Wear, History and Short Event

Summaries available to SCADA Automatically retrieve, parse and disseminate

Full-Length Event Report to enterprise PCs Display relay data on pre-formatted web pages

served from Orion.Traditional automation function, such as accessing SCADA data, retrieving time stamps and sending down IRIG-B, are also supported in the Software Suite.For more information, please visit our site.

SecuControl, Inc. i s known for thei r testblock / testplug system ITS.

Now, the company f r o m A l e x a n d r i a , VA o f f e r s a n e w terminal block with an integrated test access po int ca l led Secu Access.

Secu Access (SAX) is built for relay testing, meter testing and CT current measurement. It can be mounted on

Substation

Enterprise

PAC.SPRING.2008

15

Heat collectingelement

Direct normalradiation

Parabolicmirror

Drivemotor

from East

to WestSunpath

G

Steamturbine

Oilat 302 o C

Steam at 100 barand 390 o C

Recalentador

Condensator

Boiler Condensator

Superheater

Preheater

Oilat 395 o C

Air picture of CSP

Sun tracking principle Power plant scheme

The Spanish company Abengoa Solar, one of the leaders in developing and building large solar plants, has signed a contract with Arizona Public Service Co. (APS) – the largest energy utility in the state of Arizona (USA), to build a 280 MW solar power plant, scheduled to go into operation by 2011.The solar plant will be located about 100 km west of Phoenix, near Gila Bend, Arizona. It has been named Solana, meaning “a sunny place” in Spanish. The plant will employ a proprietary Concentrating Solar Power (CSP) trough technology developed by Abengoa Solar. It will cover a surface of around 1,900 acres. The solar trough technology uses trackers with high precision parabolic mirrors that follow the sun’s path and concentrate its energy, heating a fluid to over 700 degrees Fahrenheit and using that heat to turn steam turbines. The solar plant will also include a thermal energy storage system that allows for electricity to be produced as required,

even after the sun has set. The operational scheme is similar to that of Solnova 1 (Spain), with the addition of storage capacity as shown in the diagram below.Parabolic trough systems use an absorber tube as the collector. Solar radiation is reflected from the parabolic trough to the focal point of the parabola. The absorber tube is located at the focal point and it transfers the solar radiation energy to the working fluid. This energy is then used to run a conventional power cycle.A large benefit of parabolic trough systems compared to other solar technologies is its maturity as a technology for being installed at a commercial level. The first trough plants were installed in the US in the 1980’s and have since undergone vast improvement both in cost and efficiency.For more information on Abengoa Solar’s solar trough technology, please visit their website at: www.abengoasolar.com

1

If only 2%

of the solar

radiation from

the world’s

deserts were

used it would

be enough to

supply the

world's power

demands.The benefit of

this technology

is that it is a

conventional

thermal power

plant with a solar

energy source.

Solar through

technology plant

280 MW Sun Power Plant in Arizona, USA

tech

nolo

gy n

ews

con

side

r fu

ture

app

lica

tion

s

16

PAC.SPRING.2008

2Mitsubishi Heavy Industries, Ltd. and the Japan Aerospace Exploration Agency (JAXA) launched the super high-speed Internet satellite "KIZUNA" (WINDS) by the H-IIA Launch Vehicle No. 14 (H-IIA F14) at 5:55 p.m. on February 23, 2008 (Japan Standard Time, JST) from the Tanegashima Space Center. The launch vehicle flew smoothly and, at about 28 minutes and 3 seconds after liftoff, the separation of the KIZUNA was confirmed. We would like to express our profound appreciation for the cooperation and support of all related personnel and organizations that helped contribute to the successful launch of the KIZUNA aboard the H-IIA F14. At the time of the launch, the weather was cloudy, wind speed was 15.2 m/second from the northeast and the temperature was 9.7 degrees

Celsius. The "KIZUNA" is a communications satellite that enables super high-speed data communications of up to 1.2 Gbps to develop a society without any information availability disparity, in which everybody can equally enjoy high-speed communications wherever they live. Using an antenna for South East Asian countries, we are aiming to achieve super high-speed communications with nations in the Asia/Pacific region with which Japan has close ties.Large-volume and high-speed communications provided by the KIZUNA (WINDS) are expected to be useful in various areas. For example, we will be able to contribute to "remote medicine" that enables everybody to receive sophisticated medical treatment regardless of time and location by transmitting

clear images of the conditions of a patient to a doctor in an urban area from a remote area or island where few doctors are available. In academic and educational fields, schools and researchers in remote areas can exchange information easily. To help cope with

disasters, information can be swiftly provided through space. The Internet is now an integral part of our lives; but its infrastructure levels vary.In general, urban areas with a large population have a better Internet environment, whereas some mountainous regions and remote islands are not well-equipped with Internet infrastructure due to its costs.The KIZUNA (WINDS) does not require costly ground equipment. If you install a small antenna (about 45 cm in diameter) at your house, you can receive data at up to 155 Mbps and transmit data at up to 6 Mbps.

With a larger antenna of about 5 meters in diameter, super high-speed data communications of up to 1.2 Gbps will be available. (Such a service is mainly for organizations and companies.)

Therefore, even in some areas where major ground infrastructure for the Internet is difficult to establish, people can enjoy the same level of

Internet service as that in urban areas.

See: http://www.jaxa.jp/countdown/f14/index_e.html.

Artist Interpretation of GPS satelite

Ka-band Active Phased Array Antenna (APAA)

Ka-band Multi-based Antenna for Japan and vicinity

Solar Array Paddle (Sout Side)

Solar Array Paddle (North Side)

Ka-band Multi-based Antenna for Southeast Asia

All Composite Images: courtesy of JAXA

Artist's View: KIZUNA (WINDS) mission logo.

Japan Launches High-speed Communications Satellite

The "KIZUNA" is a

communications

satellite that

enables super

high-speed data

communications

of up to 1.2 Gbps

PAC.SPRING.2008

17

Emotiv Systems, the pioneer in brain computer interface technology, has revealed the Emotiv EPOC™, a neuroheadset that allows players to control game play with their thoughts, expressions and emotions. The Emotiv EPOC is the first high-fidelity brain computer interface (BCI) device for the video gaming market and will be available to consumers via Emotiv's web site and through selected retailers in late 2008.

The neuroheadset is a lightweight, sleek and easy-to-use wireless device, featuring sensors that detect conscious thoughts, expressions and non-conscious emotions based on electrical signals around the brain. Emotiv's technology processes these signals, enabling players to control their in-game character's expressions or actions and influence game play using their thoughts, expressions and emotions.

“Being able to control a computer with your mind is the ultimate quest of human-machine interaction,” said Nam Do, CEO of Emotiv Systems. “When integrated into games, virtual worlds and other simulated environments, this technology will have a profound impact on the user's experience.”

The Emotiv EPOC detects over 30 different expressions, emotions and actions. As a result of these detections, players will enjoy a more immersive, lifelike experience. Games will be able to respond dynamically to player emotions, enabling, for example, more sophisticated dynamic difficulty adjustment. Players can more easily simulate the aspects of gaming by controlling certain actions and expressions and manipulating objects in the game using their brains instead of a keyboard or controller.

In addition to these detections, the Emotiv EPOC incorporates a gyroscope, which enables the camera or cursor to be controlled by head motions. Emotiv and IBM announced that they intend to explore the potential of Emotiv's BCI

technology beyond the gaming market, into more strategic enterprise business markets and virtual worlds. IBM and Emotiv plan to explore how to make these environments more personal, intuitive, immersive and ultimately more lifelike. IBM also intends to explore how the Emotiv headset may be used for researching other possible applications of Emotiv's BCI technology, including virtual training and learning, collaboration, development, design and sophisticated simulation platforms for industries such as enterprise and government.

“The use of BCI technology represents a potential breakthrough in human-machine interfaces, changing the realm of possibilities not only for games, but in the way that humans and computers interact,” said Paul Ledak, vice president, IBM Digital Convergence. “As interactions in virtual environments become more complex, mice and keyboards alone may soon be inadequate. BCI is an important component of the 3D Internet and the future of virtual communication.”

The brain is made up of approximately 100 billion nerve cells, which are called neurons. When these neurons interact, an electrical impulse is emitted, which can be observed using non-invasive electroencephalography (EEG).

To share your ideas about what we can do with "mind control of computers", please send an e-mail to: editor@pacw.org

Human thoughts,

expressions and

emotions are

captured by the

neuroheadset.

3

Brain computer

interface

technology

works by

observing an

individual's

electrical brain

activity and

processing

it so that

computers can

take inputs

from the

human brain.

Mind Control of Computers

The neuroheadset is a light-

weight, sleek and easy-to-use

wireless device.

Pow

er S

yste

ms

An

alys

is

cove

r sto

ry20

PAC.SPRING.2008

by Paul F. McGuire, Ashok Gopalakrishnan,Electrocon International, Inc., Anthony T. Giuliante, ATG Consulting Inc.,

Our views are shaped by our direct experience in the field, which for some of us goes back almost as far as Dylan’s lyrics! Electrocon started developing tools for computer-aided protection engineering in 1985, working with an advisory committee of working protection engineers from ten leading North American power utilities. The goal then was a combined network and protection system model to support automated relay setting and coordination checking. Underlying the model would be a true database management system to manage the massive data. Today, network models of 2,000 to 10,000 buses with protection system models of 5,000 to 50,000 relays are common. A master library of over 5,500 manufacturer-specific relay styles supports model development, and more relays are requested and developed all the time. (Figure 3)

The advisory committee's wisdom has become more apparent and their objectives even more relevant now, when we look at the challenges our protection community is facing twenty-five years later. We'll look at a few of the problems faced by our ever-changing electric power industry, and will propose solutions from our unique perspective as software

developers and consultants who have worked with protection groups around the world.

Key issues Organizational isolation. This one might surprise you,

in this age of communication, but organizational isolation is an increasingly important problem. Most utilities are interconnected with their neighbors and are interdependent with them by virtue of the energy they buy, sell, or transport, but evidence of isolation is everywhere you look. Planning, protection, and operations are separate departments within companies. Generation, transmission, and distribution functions are all served by different entities. Business people have business goals and ask questions like, “How can we make the company more profitable?" and "How can we do our work with a smaller, more efficient staff?” Engineers have engineering goals and ask questions like, “How can we provide energy more reliably?" and "How can we design our systems the right way?”

A very important effect of organizational isolation is the failure, reluctance, or inability to share data among the stakeholders who could do a better job if they had access to it. Within a given company, for example, planning, protection, and operations are separately modeling the same network. Historically, this came about because the different objectives of each group required different models of the same equipment. Whatever the reasons, the need now is for real cooperation among these groups. For example, few protection engineers have access to power flow data that would enable them to routinely account for load current extremes in their

Downsizing is already a fact. New technologies must be provided to the remaining engineers.

1 Proportion of miscoordinated conditions, before and after Wide-Area Review

Before

After

2 Protection functions requiring recalculation

Coordinated operation Distribution or general miscoordination

Transmission miscoordination

Miscoordination cannot be solved

50 50N Recalculated Z1 Recalculated

51 51N Recalculated Z2 Recalculated

k0 Recalculated 67N Recalculated

Paul McGuire

joined Electrocon

after receiving his

MSc (EE) and EE

Professional degree

from The University

of Michigan in 1974.

He has participated

in every phase

of the work of

Electrocon, and is

currently involved

in software project

management and

licensing, managing

and recruiting staff,

customer relations

and customer tech-

nical training.

A registered profes-

sional engineer in

the State of Michi-

gan since 1984, Paul

is a member of IEEE,

CIGRE, Tau Beta Pi

engineering honor

society, Sigma Pi

Sigma physics honor

society, and

Phi Kappa Phi.

Ashok Gopala-

krishnan has a

B.E. in Electrical

Engineering with

Honors from Birla

Institute of Tech-

nology and Science

in Pilani, India, M.S.

and Ph.D. degrees in

EE from Texas A&M.

He joined Electro-

con in May 1999,

and is involved in

CAPE development,

special coordination

studies, mathema-

tical modeling of

protective relays,

macro develop-

ment, system

simulation and relay

checking studies,

and applying auto-

mation techniques

to labor-intensive

projects. He also

worked as an Appli-

cation Engineer in

the English Electric

Co. of India Ltd. (AL-

STOM), in Chennai.

He is a member of

the IEEE.

21

PAC.SPRING.2008

staffs. Retirements among engineers in the baby boomer generation in North America and Europe is another well-recognized cause. These losses combine with the diminished appeal to younger generations of careers in power engineering, particularly in countries with an affluent middle class and higher-paid alternatives.

Inadequate staffing contributes to another quality issue: in a surprising number of utilities the adequacy of the network model is marginal and the protection system model is absent or nearly so. We often see incorrect or incomplete transformer models, mutual couplings with reversed signs, and, on occasion, the absence of zero-sequence branch data.

Prot ec t ion en gineer s are le ar nin g more by on-the-job-training and starting out with less depth of underlying theory and concepts. And that's even more of a problem because fewer protection groups today have resident experts or “gurus” to call on. Then, if engineers call the relay manufacturers, they find the vendors themselves have lost expertise in their old electromechanical relay products, many of which are still in service, although their builders are long gone.

Apar t from these phenomena , there is the thought-provoking observation made to us by the late Dr. Mark Enns, an IEEE Fellow and founder of Electrocon, at the end of his career: “You just don’t see the towering intellects anymore who used to dominate our technical meetings.” We would like to think that this is more a reflection of the stage of development of power system theory and solution methods than the numbers and mental prowess of the present generation of engineers.

Imposed Solutions. A third component of change and challenge is the effect of government-imposed requirements and solutions. The issue of energy demand vs. the environment is properly one for the public arena, but that arena can only be expected to yield more restrictive government regulations. The present light precipitation may well become a blizzard. Barring a long prayed-for breakthrough in fusion power, our civilization has two sources of new baseload energy: coal and nuclear. A heavy focus will remain on alternative energy sources and conservation, as the environmental debate heats up (pun intended). This situation can only mean great turmoil in the power industry, not to mention our society.

What has it meant so far for protection engineering? We can all appreciate that sustained blackouts lead to public outcry, which in turn leads to regulations and controls intended to avert the next one. The famous blackout in North America of August 14, 2003 led to NERC Recommendation 8a which now restricts zone 3 distance element reaches and other backup protection on operationally significant lines. Protection review deadlines were mandated on every utility.

Combinations of government regulation and the NIMBY (“not in my back yard”) effect have long influenced the type and placement of large baseload plants. This has encouraged the proliferation of independent power producer plants, which are harder to accommodate and protect. Clearly this

fault calculations, which would give them better settings. Planners run electromechanical transient stability simulations without the benefit of a realistic model of the protection system, which would give more reliable warnings that the actions of protective devices may affect the scenarios being studied. Operations personnel would benefit from a timely warning if credible contingencies will overload lines to the extent of risking protective device operation. Likewise, why shouldn't SCADA systems warn the protection group about relay loading and CT rating infractions?

Companies experience parallel data sharing failures, as well. For many companies, the biggest shortcoming in the protection group’s network model is the absence of an up-to-date model of their neighbors’ systems. National security issues and competitive concerns play a role, but in many cases there are simply not enough people around to do the necessary communicating. Some utilities' security rules prevent vendors from examining and trouble-shooting their data, requiring the vendor instead to use guesswork and trial-and-error to find the cause of reported problems. And in a recent case, a company experienced measurable delays in restoring power after a blackout, because they were not allowed to know what generation was available to their system - this in the name of fair competition!

Experience Base. A second area of change and challenge for our profession is the diminishing experience base. We see several reasons for this. Utility reorganization (read downsizing) has been underway around the world since the early 1990’s and has never led to increases in engineering

3 R-X display of ABB, Siemens and SEL relays

Increasing

complexity

and additional

governmental

regulations

are today's

reality

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PAC.SPRING.2008

mitigating factors to the complexity issue. No utility uses all the available functions and most settings either don’t apply to the protection functions directly, or at least do not change from installation to installation. Those that do are critical, of course, and must be computed by the protection engineer. Certainly the cost per function has dropped significantly. Also, the evolution of digital relay complexity was driven in part by a demand to solve many different protection issues associated with various governmental and engineering requirements. It seems that increasing technical feasibility and competitive one-upmanship played a role, too. With proper care, these forces can foster creativity and efficiency.

Possible SolutionsThe challenges discussed above are complex. There is

no single, simple solution. In fact, we expect a multitude of component solutions to become prevalent in the years to come, and these will affect multiple issues at once. The drain of experience and personnel continues and is not likely to be reversed any time soon. The solutions we are able to offer are aimed at making the best use of the engineers we have.

They may be classified into three broad categories: Apply new technologies to get the right answers Use the new technologies to counter the challenge of

diminishing staff and experience Implement changes in data administration

Apply new technologies to get the right answersIt is often said that protective relaying is both an art and

a science – a science because the engineer can apply precise rules and techniques in developing relay settings; an art because, sometimes application of these precise rules does not quite work. The engineer has to use his or her experience, judgment, and knowledge of the power system to tweak or modify the relay settings to meet the desired objective.

combination has yielded boom times for the wind generation industry. How to model and protect wind farms is a hot topic in our business. The power of public opinion is exemplified by a very recent news report from the state of Virginia in the USA. The state corporation commission overrode the local utility’s $14 million proposal for a five-mile overhead transmission line in favor of a $82 million underground version. The protection engineers involved will now have the opportunity to develop their expertise in working with high-voltage cables.

Protection Complexity. We’d like to address one last force for change that certainly has brought challenge with it – the increasing technical requirements placed on power systems have led to a greater complexity of the power system in general and the protection system in particular. As population and demand grow, the electrical network becomes denser and is operated closer to design limits. As people around the world depend more on electrical energy, the societal cost of network failure motivates the design of more robust protection schemes and more of them.

How do we translate this to our experience? It’s easy to answer this with another question. Back in the early days of Bob Dylan, who would have dreamed that the half dozen or so electromechanical relays in a scheme with perhaps three to four settings each would one day be replaced by one digital relay offering 100 functions and as many as 9,000 settings? Who could have imagined setting and testing one of them? Add to this the many relay manufacturers around the globe, the fact that each one offers its own software environment to manage the settings (Vendor software), and the fact that most of today’s relays require special training to use. Keep in mind, too, that most utilities purchase relays from at least two manufacturers. Moreover, the protection schemes themselves have become more complex. Some form of teleprotection is often employed, and not just once but twice, as primary and backup. At this point, one may easily feel compassion for the dilemma faced by modern protection engineers. What can you do? Before suggesting solutions, we should mention some

4 Overcurrent relay ratcheting

Vendor Software

Overcurrent

relay ratcheting

has caused

more than one

misoperation.

by Paul F. McGuire, Ashok Gopalakrishnan,Electrocon International, Inc., Anthony T. Giuliante, ATG Consulting Inc.,

23

PAC.SPRING.2008

Therefore, we propose that engineering management focus on tools and methods that give the relay engineer confidence that the protection system he or she has designed will perform as intended. Consider going outside your departmental staff resources when your workload cannot be accomplished by existing staff.

Correct your network and protective device models. The first step in designing a protection system is to ensure that the power system network is modeled correctly. Most utilities already have a phasor-based model of their network. It makes a lot of sense to use this data, verify its accuracy, improve it where necessary, and develop or evaluate protection schemes based on it.

Transient network models are very useful in performing special studies, but require specialized modeling knowledge. While this expertise is becoming increasingly available at utilities, familiarity with phasor-based models is widespread.

With phasor-based models, the following issues need to be addressed:

Modeling of transformers and neutral circuitsAudits on the accuracy of zero-sequence mutual

coupling: Inaccurate modeling of zero-sequence mutual coupling can lead to incorrect relay settings for ground-fault protection. Many utilities have performed audits of their mutual coupling data and uncovered coordination problems due to missing couplings, reversed signs, and improper modeling of partial couplings.

Accurate modeling of the network of the neighboring utilities. This also relates to “Data Administration,” below.

Accuracy of the protection system model: In our experience, to be able to develop relay settings for the power system, the engineer must have dependable software models of relays to work with. That is, the software model of the relay must be able to capture the behavior of the actual relay, within the framework of a phasor-based analysis.

This means that realistic comparator equations, polarization methods, internal supervision, phase selection, tripping and reclosing rules, and actual settings must be used to simulate the relay in the network model. When actual setting names are used, one has a way to share settings with the manufacturer’s setting software. Traditional analysis techniques might use a few generic methods for modeling protective devices. This works well enough for electromechanical and possibly some static relays, but the multifunction digital relays require more sophisticated modeling.

Protection engineers are increasingly recognizing the value of having such detailed relay models for analysis, and are pushing vendors of analysis tools like us to develop and supply them. Another advantage of detailed models is their usefulness in allowing evaluation of a protective device before actually purchasing it.

Automate relay setting calculations. Once the network and protection models have been verified as accurate, it is possible to perform fault studies and develop protective device settings for the power system network.

The process of developing relay settings can be automated to a large extent. The computer can be used to perform large-scale fault studies. The results of these fault studies can be used to set relays based on specific company-approved rules and parameters. Where settings of one relay depend on the settings of a neighboring relay, the algorithm can attempt to coordinate the two.

Automated setting algorithms should not be expected to replace the human protection engineer. Instead, they provide a convenient way of performing routine fault studies and “first-pass” settings calculations, or can serve as a second set of eyes reviewing settings calculated manually. However, a protection engineer may be required to review special cases.

Further, the initial settings computed by the setting algorithms will need to be tested by performing automated coordination studies. This could easily necessitate adjustments in the settings.

Interactive simulations to find miscoordinations. After verifying the network and protection models and developing initial relay settings, the engineer will normally perform interactive coordination studies to ensure that adequate coordination time interval margins are maintained between primary and backup devices.

The changing electric power industry has made these ideas formulated 25 years ago all the more relevant.

Views of relay

vendor setting

software: Every

relay vendor

offers its own

tools for settings

management.

A. Giuliante

"Tony" is the Pre-

sident and founder

of ATG Consulting,

which provides spe-

cialized protection

engineering con-

sulting services to

the power industry.

Prior to forming his

company in 1995,

Tony was Executive

Vice President of

GEC ALSTHOM T&D

Inc. - Protection and

Control Division.

From 1967 to 1983,

he was employed by

General Electric and

ASEA. He is a Fellow

of IEEE and has

authored over 50

technical papers. He

is a frequent lectu-

rer on all aspects of

protective relaying,

including electro-

mechanical, solid

state, and digital

based equipment.

Giuliante is a past

Chairman of the

IEEE Power System

Relaying Committee

1993-1994, and

past Chairman of

the Relay Practices

Subcommittee. He

holds degrees of

BSEE and MSEE from

Drexel University.

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PAC.SPRING.2008

Interactive simulations may be performed to identify problem areas using the following methods:

Graphically plotting overcurrent and/or distance relay characteristics and studying their response to applied faults. (Figure 6)

Looking at device operating times on a one-line diagram of the network.

It is important to consider faults that test the coordination intervals between protective devices:

Faults at overcurrent and distance element reach points Faults at mutual coupling separation points Faults that must be cleared by sequential breaker

operations Faults in the presence of contingencies like minimum

infeed conditions, outaged and grounded mutually coupled lines, etc.

An interactive study with faults applied by hand will give engineers a very good idea of the coordination problems that they might face. But the number of conditions to be tested can quickly become quite large and impractical to study manually. Such simulations may not be adequate and should be repeated over a wide-area of the network, if not the entire network.

Conduct wide-area coordination reviews. Protective system reliability can be measurably improved by combining the unified network and protection system model, detailed protective device models, and the power of modern computer technology to evaluate protection system performance to uncover conditions of miscoordination and, on occasion, relay design problems. Where such reviews were formerly considered a worthy but impractical goal, they are now possible and of demonstrable benefit. In one documented case, a wide-area coordination study revealed that 16% of the applied faults resulted in a miscoordinated condition. (Figures 1 and 2) The miscoordinations were mostly due to incorrect settings in the neutral directional overcurrent (67N) and zone 2 distance elements. By identifying these conditions, the utility was able to adjust the relay settings and reduce the miscoordination percentage to around 2%.

One of the interesting results of this study was the uncovering of a design problem in a distance relay, later verified by an actual misoperation in the field of the same relay. The cause was unexpected behavior of the polarizing quantity used by a ground distance element, which only a detailed relay model could uncover. This led the utility to temporarily disable the offending element in all the relays of that type until a fix was obtained from the manufacturer.

Use computer tools to respond more efficiently to government regulations. In the USA and Canada, the aftermath of the August 14, 2003 Northeast blackout brought new regulations that utilities had to comply with. One was directed at protection engineers – namely, NERC Recommendation 8a for zone 3 (backup protection) relays. Utilities with existing network and protection system models could easily automate a system-wide review to comply with the recommendation.

Use computer tools to conduct post mortem analyses. An accurate, combined network/protection system model can be a valuable tool for studying questionable relay operations. In one case we studied, an existing zone 1 relay (an electromechanical design, with a mho-supervised reactance characteristic) was slow to operate for a resistive fault. The fault was at the reach limit of the mho supervisor, which was not designed to use the prefault memory voltage for polarization. This was verified by subsequent simulation. Simulations also showed that using a digital relay with memory polarization would result in fast operation for the same fault (Figure 5). So proper representation of the equations behind the relay’s operating characteristics is necessary.

Use new technologies to address the challenge of diminishing staff and experience

The methods and tools described above are also valuable as training tools.

1. Detailed models of protective relays in a master library can help counter the burden of learning relay details the hard way, particularly when the model is documented. This serves as a knowledge base when consulting an expert is not an option.

Plot of dyna-

mic expansion

of digital

mho element

predicting

operation for

fault near

balance point,

where the

actual self-

polarized

electromecha-

nical relay

operated too

slowly.

5 Dynamic expansion of digital Mho element

Engineers must have tools to cope with their increasingly complex environment.

25

PAC.SPRING.2008

2. Simulating the whole protection system is analogous to using a flight simulator – a safe environment for engineering training, and for studying the effect of relay settings on wide-area coordination.

3. Stored and properly documented setting techniques can speed the setting and documenting processes, and also serve as a teaching tool for younger engineers. We aren’t advocating this training technique as a replacement for the resident expert but as a supplement and a backup for when there is no expert.

4. A common database environment can unify and coordinate the management of settings to a useful degree without needing to replace the multi-vendor setting software communication environments - an unrealistic objective in a competitive world.

5. The application of advanced computer methods, not only to protection but throughout power system engineering, can attract prospective engineers to our profession from a generation already enamored of computer technology.

Implement changes in data administrationSoftware can’t provide the incentive for organizations

to cooperate, but it can make the mechanics of cooperation easier. We discuss here some of the advantages that might be gained by sharing both network and protection data within different groups in a company and among companies.

1. Data must be maintained by those who use it and who know the system best, but data could be stored, shared, and kept secure at a higher level than the individual groups or their companies. Multi-user database management systems are common and must not be viewed as a constraint.

6 Dynamic display of primary/backup TOC element coordination

Techniques are in use now that support a nearly unlimited mixture of construction scenarios, generation levels, and alternative network configurations. Database merge facilities exist. What is lacking is centralized data storage and sharing. Formalizing higher level storage and sharing won’t lead to fewer personnel; in fact, there may be more of a need for engineering specialists, but it should lessen user tolerance for marginally adequate network models and overcome the poor quality neighbor models that are common today. It would also provide one path for sharing power flow data with the protection engineers. To the credit of the utilities involved, there are a number of less formal initiatives now underway to share short-circuit network models among the participants. (Planning groups have done this for years.)

2. Share protection system models with planning groups whose transient stability (TS) and electromagnetic transient studies would benefit from realistic representation of that system. Existing TS programs have only rudimentary models of a few relays, whereas direct links between the protection system model and the TS time-domain model could lead to important insights. We also think this would be a positive step toward increasing awareness of likely protection system response in operations centers, the lack of which has played a role in some blackouts.

3. Share protection models with Operations departments using a link from the SCADA system to obtain actual network conditions and a link to the SCADA interface to warn of the threat of load-induced misoperations, to monitor protection system performance, and to facilitate rapid fault locating thereby minimizing repair and down time.

A computer

display can

quickly

present

response

time

changes

as a fault

is dragged

about the

network.

IEC

618

50 u

pdat

e

by Christoph Brunner

27

PAC.SPRING.2008

I n t h e l a s t c o l u m n I addressed a specific technical topic related to IEC 61850 – the modelling of functional hierarchies as it is currently under discussion for Edition 2 of the standard. This time, I will focus on an update of major activities related to IEC 61850. But in order to understand the terminology, it might be a good idea to explain the life cycle of IEC documents.

An IEC standard is initiated by an approved new work item. Note that in IEC, the votes are done by the national committees that are member of a technical committee (TC) – in the case of IEC 61850, the technical committee is TC 57. Every national committee has one vote.

Once a work is approved, it is assigned to an existing working group, or a new working group is created to prepare the standard. The drafts are first circulated internal to the working group and when a certain level of maturity is reached, a committee draft for comment (CD) is circulated to the national committees.

A CD is not necessarily yet the complete and final document. The purpose of the CD is to show the direction of the future standard and

to get feedback from a broader range of experts.

The next step is the CDV – Committee Draft for Voting. That is already a mature draft, the countries have to give a vote within five month, and the vote can include comments. If the CDV is approved, only changes requested in the comments are allowed and the next step is the FDIS (Final Draft International Standard). Here no technical changes are possible anymore unless the FDIS is refused and the document is sent back to the CDV stage. Shortly after the approval of the FDIS, the standard will be published.

E v e r y s t a n d a r d h a s a maintenance date. At that time, the standard can be reconfirmed as is, withdrawn or a new Edition can be prepared.Most of the parts that have been published in IEC 61850 will be issued as Edition 2. With the Edition 2 we will solve technical issues (TISSUES) identified during the first implementations of IEC 61850, but we will address as well requirements concerning the use of IEC 61850 in domains other than substation automation. Edition 2 of part 6 has already been circulated as CDV, we are currently finalizing

the part 7 (7-1 to 7-4). Part 5, 8-1 and 9-2 shall follow as CDV a few weeks later. For the other parts we will prepare CDs.

There will as well some new parts be added to IEC 61850. I will report on that in a later issue. For this time, I would like to point your attention to the CIGRE conference hold every second year in Paris. This summer, the study committee B5 has selected as preferential topic 1 "Impact of process-bus (IEC61850-9-2) on protection and substation automation systems".

Six interesting papers have been submitted that are discussing different approaches for system architectures when using IEC 61850-9-2 as serial connection between bay level devices and current and voltage sensors. If you plan to visit the CIGRE conference, this session on Wednesday, August 27, will certainly include many interesting discussions. And if you attend the CIGRE conference, do not forget to visit in the exhibition the booth of the UCA International users’ group – the users group for IEC 61850, CIM and open AMI.

I look forward to seeing you there!

The Life Cycle of a Standard

An international standard is the result of the efforts of many experts in the problem domain that it addresses. The IEC standardization process is briefly described bellow. It follows steps that ensure the coverage of dif-ferent aspects and the points of view of participating countries around the world.

Modern Intelligent Electronic De-

vices, encountered at a substation,

conform to a common architecture:

A processor directs Analog and Binary

Input subsystems to acquire data from

the power system; a Binary Output

provides system control and Com-

munication Subsystem interfaces

to Substation Automation, SCADA

and Energy Management Systems.

The rigid, real time performance demands placed on Protective Relays, Remote Ter-

minal Units, Communication links, SCADA and EMS systems, coupled with harsh

operating environment, make these systems complex to design, install and operate.

This article describes real life episodes as seen through the eye of equipment provider.

BINARYINTPUTSUBSYSTEM

BINARYOUTPUTSUBSYSTEM

ANALOGINTPUTSUBSYSTEM

COMMUNICATION SUBSYSTEM

SUBSTATIONAUTOMATION

SCADA, EMS

OPERATOR INTERFACE

PROCESSOR

Power system

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by Janusz W. Dzieduszko, Quanta Technology, USA

PAC.SPRING.2008

1 IED architecture

Substation "Horror

Stories" - a Manufacturer's

Perspective

TX

To Master

RX

TX

To RTU

RX

PAC.SPRING.2008

29

False Breaker Trip ReportingA Supervisory Control (early

1970’s predecessor of SCADA) system at a major Electric Utility reported circuit breaker operations at several substations occurring at random, over the span of several weeks.

Subsequent inspection of the breaker control equipment at those substations revealed that no breaker operations took place and a Supervisory Control equipment was providing false information. Several dozens of these systems were purchased and installed by that Utility. Naturally, the reliabili-ty of the equipment and the qualifi-cations of the personnel involved in its design and manufacturing were seriously challenged by the Utility management.

It has been mildly suggested dur-ing the meeting preceding field in-vestigations that the equipment be put in perfect operating condition by the “end of the week” or replaced with similar product made by those “who know what they are doing”. The diagram in Figure 5 depicts a typical system configuration.

The rest of the day was spent at the Master Station ( a 90” tall cabinet full of PC cards with mostly discrete transistors and indicating lights). The oscilloscope measure-ments indicated proper signal levels suggesting that the problem was on the RTU level. It is worth men-tioning here that the understanding of the substation noise was rather sketchy in those days and the equip-ment tended to be overdesigned.

Similar investigations were per-formed at the Remote Terminal Units in question. Oscilloscope measurements provided no clues. An MG-6 relay connected in “buzz-er” mode was used to generate a substantial amount of noise; again no false operations were observed.

As the week came to a close, the 52a wiring (see above) check was done in desperation. The RTU ter-minals looked fine; however, a walk to the breaker control box in the

yard was very fruitful; the corre-sponding terminals had loose screw connections! It was discovered later that the same problem existed at all suspected RTU locations. End re-sult: happy Customer !

Lesson #1: Pay attention to the simplest element of your system

Continuous alarmThe equipment and location

were the same as in the previous episode. Under normal operating conditions the alarm or change of contact status was reported by an RTU and acknowledged by a Mas-ter Station to reset the alarm. The communication links to the RTUs were 60mA loops operating at 50 bps (sic!) connected as shown in Fig ure 2. The transmit TX and receive RX devices were identical mercury wetted contact relays with plug-in octal bases.

One of the RTUs reported an alarm but the Master Station ac-knowledgement failed to reset it, and thus an alarm condition persisted at the RTU. The system operator would dispatch a techni-cian to the RTU who subsequently swapped TX and RX relays, there-by eliminating the problem.

Several days or so later the same problem would occur, so the same approach was used and the prob-lem cured again. Note that TX and RX relays were now in their origi-nal position!

During the field trip to the sub-station, the real problem was deter-mined to be a solder whisker on a printed circuit board extending to the adjacent trace, as shown in Fig-ure 4.

During abnormal system behav-ior with the RTU enclosure sealed, the internal temperature caused the solder whisker to expand, touch-ing the adjacent PCB trace and disabling the alarm acknowledge circuit. Opening the enclosure to swap TX and RX relays lowered the temperature sufficiently to con-tract the whisker, thereby “fixing” the problem.

Lesson #2: The “repair” you just made, may not have anything to do with the problem!

Printed circuit board swapping

One of the most commonly used methods of system trouble-shooting is “board swapping”; here is another real life story.

A second generation SCADA system, with computer based Mas-ter and integrated circuit CMOS RTUs, was being installed at a me-dium sized municipal utility. The system configuration was similar to Figure 5 with four RTUs on each communication link. The RTU conformed to Figure 1, with the processor section consisting of 3 printed circuit boards: A, B and C.

A portable Master simulator was used to commission the RTUs. (Figure 3) Here is the approximate sequence of events used in initial troubleshooting:

RTU #1 was verified to perform properly.

2 60 mA Loop

One of the most commonly

used methods of system

troubleshooting is “board swapping”

Janusz Dzieduszko

is M.S.E.E. graduate

of the Academy of

Mining and Metal-

lurgy in Cracow.

He has over 40

years of experience

in engineering

management and

design in Substation

Automation. Janusz

is currently Con-

sultant with USA

in Raleigh, NC. He

worked with: ABB,

Westinghouse,GE

and BBC. He holds

five patents and is

authored several

papers in Substation

Automation. His bi-

ography is included

in Marquis’ “Who is

who in the World”

and “Who is Who in

America”.

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PAC.SPRING.2008

retries and after failure, declared RTU or communication line “out of service”. This performance (even with 99.9992% availability!) was unacceptable to the user. Consider-able time was invested in analysis of data communication channels. No obvious sources of suspected inter-ference were found; all vital param-eters were well within limits. The communication FSK modem was blamed, as 1800 bps operation in those days was at the cutting edge of technology. Many adjustments to compromise delay equalizer failed to improve the performance.

A legal action with $6 million liability was suggested at various management levels.

At that time the author was vol-unteered to take a look at the prob-lem. From the very beginning he suspected factors other than those outlined above.

How do you “catch” the instant of 120 msec occurring once or twice in a 24-hour period with sufficient resolution to decode 555 msec (1 bit time at 1800 bps)? (Remember, those were the days before logic analyzers, and storage oscilloscope was the best tool available.)

Here is the brief description of a rather lengthy investigation process:

During a trip to a local audio equipment rental facility, a stereo tape recorder and stereo earphones were obtained and connected to the communication lines:

After some practice, a rhythm of “good” and “bad” communication exchanges was determined. A hu-man ear is an excellent integrator!

Occurrences of communica-tion problems were correlated to

nent platform with vertical pins in-serted in the IC socket. The top pins were jumpered with the bare wire and hand soldered. The unused connections, as determined by ad-dress decoding, were clipped off.

It was found that the jumpers described above had cold solder connections causing intermittent problems. Furthermore, these innocent jumpers were subcon-sciously removed from the “bad” boards and transferred to the “good” boards, always remaining with RTU#2.

Lesson #3: Be aware of vari-ables introduced during board swapping.

I n t e r m i t t e n t d a t a communication

A large process control system as shown on the diagram in Figure 6 was installed. A major computer manufacturer provided main con-trol processors, SYSTEM 370 and SYSTEM 7 and software; COMM INTFCE and RTUs were supplied by (then) a Major SCADA Com-pany. RTU communication was via copper shielded twisted pairs with a maximum distance of 5 km. Asynchronous frequency shift (FSK) modems operating at 1800 bps, with mark and space frequen-cies of 1200 and 2200 Hz respec-tively, were used. Connection was 4 wire with separate pairs for data transmit and receive. RTU commu-nication used popular 32-bit proto-col with 2 start, 24 data, 5 CRC and 1 stop bits. SYSTEM 7 to COMM INTFCE data link was parallel with 12 bit data lines and several control lines.

During final system start-up, a vicious communication problem was uncovered.

Several (2 to 4) times per day COMM INTFCE reported CRC (cyclic redundancy check) errors on data acquisition; this condition existed in short bursts of 120 to 180 msec.

System software invoked error recovery initiating 3 data retrieval

RTU#2 intermittently did not respond to the simulator.

The known reference set of boards(A,B,C)was inserted in RTU#2; causing the problem as in step 2.

The set of boards from RTU#1 was transferred to RTU#2; causing the problem as in step 2.

The set of boards from RTU#2 was t ransfer red to RT U#1; RTU#1 checked out OK!

The backplane (motherboard) of RTU#2 was replaced and the prob-lem still existed as in steps 2,3, 4!

Similar situations were repeated at other RTU locations.

The careful reader at this mo-ment agrees that some mysterious events occur at those substations! Utility engineers reported later that the manufacturer’s field en-gineer had five sets of boards and backplanes in his automobile, and was driving at 70 mph across town (from one RTU to another) with a wild expression on his face!

Here is the real problem as found many days later:

To operate on a shared commu-nication channel, the RTUs needed unique addresses. The addressing was accomplished using a compo-

Be aware of variables introduced during board swapping.

4 Solder whisker

A B CRTU #1

A B CRTU #2

3Master simulator

RTU RTU RTU

52a

RTU

MASTERSTATION

PAC.SPRING.2008

31

5 Typical SCADA configuration

7 Error sections of tape playback

6 Process control system

SYSREM 370 RTUsSYSREM 7 COMM INTCE

TAPE RECORDER FSK MODEM OSCILLOSCOPE

A

B

RCVRINPUT

DATA OUT

AUDIO OUT

AUDIO OUT

PAC.SPRING.2008

less

on le

arne

dPr

otec

tion

Fai

lure

32

the tape counter on tape recorder. Known sections of tape were played back as in Figure 7. Normal data retrieval sequence consisted of one 32 bit request sent to RTU, fol-lowed by up to 8 32 bit responses from RTU.

RTU ResponseData Request

It was determined that during the communication problems one 32-bit data request was repeated as shown:

RTU ResponseData Request

The “phantom” request, shown as shaded area, was later attributed to the race condition on the COMM INTFCE parallel to serial converter when “write” signal exceeded max-imum allowable duration.

As a result the receiver clock recovery mechanism was disabled and the incoming RTU response was received using transmit clock! No wonder massive CRC errors were encountered. It was later determined that the duration of

“write” signal was affected by SYS-TEM 7 loading. To make COMM INTFCE immune to variations of this signal, a monostable multi-vibrator (one shot) was added, thus eliminating the entire problem.

The author fondly recalls having to work 14 hours on the Bicenten-nial Fourth of July 1976!

Lesson #4: Design your inter-faces with care, protect yourself! Do not be afraid to use unconventional tools.

Fiber optic noise immunityIndustry’s first Integrated Sub-

station Protection and Control system was designed as an EPRI project in early to mid 1980s using the then state of the art micropro-cessor 8086 16-bit technology. Due to processing limitations, (8086 operating at 6MHz and memory of 128 kbytes) multiple processors (up to 6) shared the computational loads and were configured in shared memory clusters.Figure 8 shows a simplified diagram of the system.

The Station Computer provided operator interface for substation management and was connected to Protection Clusters via coaxial cable

Data Highway communicating at 1Mbps. Protection Clusters’ func-tion was protection and control; Data Acquisition Units interfaced to the power system and were con-nected via fiber optic Data Links operating at 1Mbps to Protection Clusters.

Fiber optic Clock and Arbitra-tion Bus synchronized the system and allowed for intercluster com-munication for time critical con-trol operations.The system was designed with interoperability in mind 20 years before IEC 61850; the elements shown in dotted lines were provided by another manu-facturer and were successfully inte-grated into the system during final installation at a major 500 kV sub-

When things do not make sense,

you have made a wrong

assumption!

8 Simplified diagram of the system

Protection clusters

Data acquisiton units

data highwayBUS

Clock & arbitration bus

data links

XFMR LINEStation Computer

500 kVYardDAU

A/D

µP

FIELDINPUTS

MUX

REF

PAC.SPRING.2008

33

station.In the final phase of testing at the factory, the system suddenly started to “crash” several times per day.Extensive use of fiber optics assured very high degree of noise immunity, thus exonerating sys-tem hardware.The interaction of multiple processors in clusters was suspected and analyzed over the period of days; no obvious reasons were found.

It was observed later that the crashes occurred during late morn-ing, and were later correlated to the passing of a Mail Robot vehicle near the system. The vehicle has a motor that generates EM interference; the system hardware became a prime suspect. Very soon the problem was solved:

A robot (in addition to motor) had a safety strobe light that was penetrating one of the Protection Clusters via partially open enclo-sure rear door. These light pulses were “read” as spurious interrupts by a fiber optic receiver left open for the integration of other manu-facturer’s cluster into the system. A strategically placed piece of electri-cal tape cured the problem.

Lesson #5: Do not take any-thing for granted.

False system operationsSome time following successful

installation and integration at the substation, the system described in the previous chapter began to issue false breaker trip commands.

These occurrences were rare (2 to 3 weeks apart), random, and were traced down to all protection clusters. Obviously, much energy, time, and money was invested in attempts to eliminate this unpleas-ant phenomenon. The complexity of the system opened the door to various theories in two basic areas:

Substation noise System software bug

The system passed extensive factory type testing including SWC, Fast Transient, RFI and tem-perature limits.

Massive utilization of fiber op-

tics for system interfaces eliminated a wide area of suspicion. The sys-tem was designed by software and hardware engineers with vast expe-rience in substation requirements.

Software “traps” were added to the system, logic analyzers initial-ized to trigger on suspected events were installed, and additional fil-tering and shielding were tried; no answers were obtained. The last el-ement analyzed by the author was Analog Input card in Data Acquisi-tion Unit. (Figure 9)

The microprocessor controlled the A/D conversion process, and using precision REF inputs, pro-vided continuous A/D calibration for temperature and component tolerance drifts.

The calibration was in the form of: Where y – A/D output; a – gain; x – Analog input; b – offset.The A/D had 16-bit output, while the microprocessor was 8049 fam-ily 8-bit machine. All arithmetic operations were, therefore, using double precision arithmetic (low byte, high byte). 15 07 High byte 0 7 Low byte 0

The assembly language pro-gramming was used.Taking the program listings and processor ref-erence manual home, away from the day to day distractions, after several hours of careful instruction by instruction study, the resound-ing EUREKA! followed.

It was found that doing ax + b addition, the processor checked for possible register overflow (i.e. the result possibly exceeding 15 bit number).

Bit 7 of HIGH BYTE set to “1” indicated that fact, and should re-sult in setting the register to full scale (7FFFhex).

Instead of testing that bit, bit 7 of LOW BYTE was tested in er-ror (otherwise known as software “bug”).

Full scale input to the A/D was 5 V corresponding to 30 p.u. (150

9 Analog Input

A rms) for analog inputs. It is easy to compute that the input of ap-proximately 20 mV (0.585 A rms) sets bit 7 of LOW BYTE to a “1”, thus causing the false assumption of a huge fault current (equal or greater then 30 p.u.) and subse-quent system trip.

Lesson #6: Pay attention to processor architecture. Avoid fixed-point arithmetic.

I Thessalonians 5:21

And a quote from the past:

“Omnia autem probate quod bonum est

tenete.”“Prove all things;

hold fast that which is good.”

34

by Clare Duffy, ESBI, Ireland

blac

kout

Wat

ch

PAC.SPRING.2008

systempoweroutages

Analysis of system power outages can help us learn

and avoid similar events in the future. If you have

information on any blackouts, please e-mail to:

http://editor@pacw.org

A blackout that struck Carcar City and 16 towns in southern Cebu was caused by the torching of a 69 kV wooden electric pole that created a “domino effect” and brought down with it two other nearby poles. The power outage lasted nearly 14 h.

A blackout hit Cape Town at 8.45 PM on Friday and lasted until the early hours of Saturday. Eskom apologized to its customers for the technical fault involving a conductor at the major subst at ion of Muldersvlei-Acacia, plunging most of the city into darkness.

Human error was the cause of a state-wide blackout that started at 1:09 PM and affected about 584,000 FP&L customers and an additional half-million across three other utilities. It began with a field engineer diagnosing a switch that had malfunctioned at a substation in West Miami. Against company rules he had disabled both the primary and backup protection. The fault affected 26 transmission lines and 38 substations. One of the substations affected serves three of the generation units at Turkey Point, including a natural gas unit, as well as both nuclear units, which

St. Andrew,Jamaica6 April,2008

Florida, USA26 February,

2008

Carcar City,Philippinies 30 January,

2008

PAC.SPRING.2008

systemoutages

Time and

location of the

System & Power

Disturbances in

2008

shut down automatically. Two other generation plants were affected and the system lost a total of 3,400 MW of generating capacity.

A row over unpaid bills sparked a huge power blackout in Pakistan's biggest city, Karachi, leaving most of its 12 million residents without electricity. The outage came after Pakistan's main power utility

accused the electricity company supplying the southern port of refusing to settle debts of more than half a million dollars.

Following a blackout that lasted several hours on 14 March, Delhi and its satellite towns were subjected to another power shutdown on the morning of 16 March, as more than thirty seven 400 kV transmission lines tripped. Most parts of West, East and North Delhi experienced prolonged power cuts. The tripping of lines was blamed on flash-over on the insulators in the presence of fog and pollutants in the atmosphere.

Residents in Kingston and St Andrew were left w ithout electricity for close to four hours after a fault with one of the company's transformers triggered the outage. A zonal strategy saved Jamaica from another island wide power outage.

South African power utility Eskom will start nationwide planned blackouts from March 31

to reduce demand, as Africa's biggest economy st r ug gles w ith an electricity crisis. The utility said it would implement rolling blackouts - known as load shedding in South Africa - for at least three months to reduce electricity demand to manageable levels.

Shortly after 9 AM a falling construction crane cut an electricity transmission line and plunged most of the Philippine capital into a three-hour blackout Friday, affecting about 70 percent of metropolitan Manila and triggering an automatic shutdown at several power plants. The outage halted trains and disrupted traffic, leaving commuters stranded throughout the city.

Thieves apparently looking for scrap metal triggered a blackout across most of Sabah state in eastern Malaysia when they removed iron beams from a 132 kV tower, causing it to collapse and triggering a domino effect that left 300 thousand customers in the entire state of Borneo Island without power.

Kuala Lampur,Malaysia 21 April ,

2008

ManilaPhilippinies

11 April,2008

Karachi,Pakistan

26 February,2008

New Delhi, India

16 March,2008

Cape Town,South Africa 1 February,

2008

South Africa 31 March,

2008

36

Ch

alle

nge

s

Syst

em P

rote

ctio

n

PAC.SPRING.2008

by Javier Amantegui, Iberdrola Distribution, Spain

increase in load of 32% in the last seven years. This increase has resulted in a reduction of critical clearing times and new requirements for protection.

Protection assets are becoming older. According to aforementioned CIGRE Task Force, 40 to 50% of the protection relays of some utilities were electromechanical and more than 30 years old.

Taking these two facts into account, we must think of protection as a strategic asset that should be able to cope with more and more demanding requirements from the grid now and in the future. In order to achieve this, state of the art protection systems will need to be installed in the grid.

But let’s go even further -- improvements in reliability that can be obtained from new digital relays. According to Iberdrola’s experience with causes of protection failure in new substations, only around 15% of the failures are internal to the relays. However, 40% of the failures are outside the relays, mainly due to wiring. and 45% of the failures are caused by setting errors. The good news is that 85% of these failures could be eliminated by the utility.

Consider the three main ways to achieve reliability improvement:

Standardization: in order to reduce engineering and construction errors.

Commissioning testing: in order to identify and correct these errors.

Before considering the application of relays, we should answer a basic question:

What is the main requirement for protection from the utilities’ point of view? In my opinion, there is no doubt that reliability is the main requirement.

When there is a fault in the grid, everybody expects relays to trip quickly and with selectivity no matter the kind of fault or the initial cost of protection.

According to a survey carried out in eight utilities by the CIGRE Task Force 34.06 (2002), reliability indexes were between 92% and 97.5%. The three utilities with the best indexes, above 97%, had carried out an extensive refurbishment program of their protection system. Although this may seem obvious, it must be emphasized that refurbishment is the easiest way to achieve protection reliability improvement.

There are two main drivers for refurbishment:. Measurement EquipmentThe measurement equipment used is as follows:

Increasing protection requirements are coming from the grid. For example, in the case of Spain there has been an

Challenges and Opportunities

utilities face by using modern

protection and control systems

pictures courtesy to :Iberdrola

1 Human Machine Interface 2 IED Panels - 1/2

I believe

that the only

solution to

the problems

is a black-box

approach.

37

PAC.SPRING.2008

Relays become obsolete quite rapidly. And within the life span of each relay, versions are changed several times. Version control is probably the main problem with digital technology.

Protection people need new skills to deal with Information Technology. For example, in the past it was quite easy to change a wired signal connected to a relay. Now, to change the configuration of a multi-vendor SAS could be a really complex task.

Of course, there are also the well-known constraints of less commissioning time, fewer resources and difficulties to recruit new staff; but these are not only related to digital technology.

How can we solve all these problems? I believe that the only solution is a black-box approach. Protection engineers should be able to work with different models of relays in a conceptual way. We should be able to work using the same tools and with the same functional models. This will allow us to gain experience and give added value to our work. Please try to focus on this basic knowledge and try to avoid spending time with details that will be useless in the short term.

Going back to the improvement based on standardization, in Iberdrola we think that the key to this approach is standardization based on IEC 61850. That is the reason why we have developed a multivendor IEC 61850 based SAS. The first substation was commissioned last year and this year we have three new IEC 61850 substations projects.

In conclusion, my opinion regarding the application of digital protection and control by utilities could be summed up in two ideas:

Protection is the strategic asset to support the new requirements and constraints on the grid, now and in the future.

Protection engineers have never before had so many and such challenging opportunities to improve reliability.

Fault analysis: in order to detect any faulty operation Modern protection and control systems offer new

opportunities for improvement in these three approaches. Here are examples of best practices:

StandardizationRed Eléctrica de España (REE), which is the TSO in Spain,

is carrying out a very ambitious protection refurbishment campaign in the whole transmission system. The key to achieving their goal is standardization and wiring reduction. This standardization has allowed REE to increase the reliability of their protection system and to fulfill deadlines with their refurbishment program.

Commissioning testing New devices based on IEC 61850 allow for new

functionality. Therefore testing can be carried out directly from the configuration files of the substation and completed automatically. This opens new opportunities to reduce testing time and more efficient identification of failures.

Fault analysisThese days, with new digital protection, the problem is

not having the information, but how to deal with it. In this respect, we think that protection management

systems are crucial. The system we are using in Iberdrola covers the functions of communication with relays, fault analysis tools, setting database and fault database. This system is the heart of our protection organization and helps us to achieve our goal of attending and correcting significant protection failures in 24 hours.

A second step would be to develop analysis tools to automatically help the engineer with a diagnosis. However, in order to do this, standardization is essential

It’s clear that digital technology offers new opportunities for improvement; there are also several drawbacks, related with people. Protection engineers have difficulties with the new protection constraints such as:

Complexity. A modern relay usually has 200 or more parameters to be adjusted.

Biography Javier Amantegui

Javier Amantegui

graduated as an

electrical engineer

from the Escuela

Superior de Ingeni­

eros de Bilbao. He

joined Iberdrola in

1997 and worked in

the areas of SCADA

hardware mainte­

nance, protection,

power quality and

metering. At pre­

sent he is manager

of the Protection

and Technical Assis­

tance Department

in Iberdrola Distri­

bution in Spain. He

has been involved

in CIGRE activities

since 1988 and he

will be the new

SC B5 Chairman

from August 2008

onwards.

3 Substation Mercedes 4 Wind farm

Precise Fault Locator

by Dr. Juergen Holbach and Michael Claus, Siemens PT&D, USA

PAC.SPRING.2008

38 39

EAFTransformers

Fault locator functionality is a standard feature in modern numerical feeder

protection devices for transmission systems. It is common practice to calculate the

fault location via an impedance measurement separately at each line end. All

calculation techniques used to date in this “single ended” fault location approach

exhibit limited accuracy. Hereafter, the fundamental improvement provided by

the “two ended” fault locator,

which in addition uses the

measured values from the

opposite line end, are described.

Single-ended fault locators are normally based on an impedance measurement. Only the fault reactance is used to determine the distance to the fault. The distance protection is based on the same principle. All protection engineers know about the limitations of this measurement and use only 80-90% of the line impedance for a zone 1 setting. Even more difficult for the fault locator is, that an accurate measurement is expected along the whole line and not only on one

two-endphasor measurements

with

Precise Fault Locator

10 9 8 7 6 5 4 3 2 1 0 I I I I I I I I 1 2 3 4 5 6 7 8

double-sided: Type=L2L3, Location=5.0 miles, If=19.6 kA, Rf=0.1 Ohm

single-sided (K2): Type=L2L3, Location=4.4 miles, If=19.6 kA, Rf=0.4 Ohm

single-sided (K1): Type=L2L3E, Location=5.4 miles

K1:Spannung uL1 K1:Spannung uL2 K1:Spannung uL3

20 0-20-40

20 0-20-40

K1: double-ended K1/K2: single ended from both ends

miles

Eval

uatio

n

Current IA Current IB Current IC

t/s-0.06 -0.05 -0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04 0.05 0.06

I/A

-40

-20

0

20

Voltage VA Voltage VB Voltage VC

t/s-0.06 -0.05 -0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04 0.05 0.06

U/V

-100

-50

0

50

Current IA Current IB Current IC

t/s-0.06 -0.05 -0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04 0.05 0.06

I/A

-40

-20

0

20

Voltage VA Voltage VB Voltage VC

t/s-0.06 -0.05 -0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04 0.05 0.06

U/V

-100

-50

0

50

K1:Strom iL1 K1:Strom iL2 K1:Strom iL3

by Dr. Juergen Holbach and Michael Claus, Siemens PT&D, USA

40an

alys

isFa

ult

Loc

ator

PAC.SPRING.2008

location. The effective ground impedance is often not proportionally distributed along the line length, as it may vary significantly depending on the consistency of the ground (sand, rocks, water, snow) and the type of grounding applied (tower grounding, parallel cable screens, metal pipes).

2. Parallel linesIn the case of parallel lines, inductive coupling of the

current circuits is present. On transposed lines, only the zero sequence system is negatively influenced by this coupling. For load and faults that do not involve ground, the influence of the parallel line may be neglected. With ground faults in the other hand, this coupling may cause substantial errors in the measurement. On a 400 kV double circuit overhead line measuring errors at the end of the line may for example be as large as 35% /1/ Some devices with distance protection functionality have a measuring input that may be applied to measure the ground current of the parallel line. With this measured ground current of the parallel line the impedance calculation may be adapted such that the parallel line coupling is compensated. This parallel line compensation can however frequently not be implemented.

The reasons for this are that only a section of the line is in parallel to another line, two or more parallel lines exist or the connection of current transformer circuit between individual feeder bays is not desired by the user for operational reasons.

While the selective distance protection function can still be implemented by appropriate zone setting in combination with teleprotection systems, the results of the fault locator without parallel line compensation is often not satisfactory.

setting point like on the distance protection function. This is especially a challenge for lines with a non linear impedance distribution along the line.

In the diagrams of figure 1 is an evolving fault shown on a 50 miles long line. The fault was at 5 miles from the shown location. The figure shows the signals of a C-G fault on the parallel line with a BC evolving fault on the actual line after approx 2.5 cycles.

The fault locator result from the single ended fault location from both ends (red) and the double ended fault locator (blue/green) are presented in Figure 2.

The common factors that influence the accuracy are described below. Hereafter, the fundamental improvement provided by the “two ended” fault locator, which in addition uses the measured values from the opposite line end, are described.

Factors that influence accuracy of “single-ended” fault locator

In the following the most important error sources for the result of a fault locators are listed.

1. Residual Compensation (ZG/ZL, k0)The majority of the short circuits that occur in the

transmission system are ground faults. The accuracy of the “single ended” fault location largely depends on the zero sequence compensation setting for the ground impedance when the short circuit involves ground. The exact value of this compensation factor is often not known. Even if the ground impedance of the line is determined by measuring the zero sequence impedance prior to commissioning – which is usually not done due to time and cost constraints – the actual effect of ground impedance during the short circuit may be severely dependent on the actual fault

Dr. Juergen Holbach was born in

Germany in 1961.

He graduated from

the University of

Berlin with a PhD

in Electrical Engi-

neering. He joint

the Siemens AG in

1992 as a develop-

ment engineer in

Berlin Germany. In

1994 he moved to

the product mana-

gement group for

protection relays

in Nuernberg

Germany. Since

2000 he works

for Siemens in the

US out of Raleigh

North Carolina.

Currents and voltages Fault locator results1 2signals of a C-G fault on the parallel line and BC evolving fault on the actual line after 2.5 cycles

from single ended fault location from both ends and double ended fault locator

ILoad

ZLBZLA

VBVA

IA IBRF

Line impedance Faulr resistance Voltage

by Dr. Juergen Holbach and Michael Claus, Siemens PT&D, USA

PAC.SPRING.2008

41

through the ohmig fault resistance RF causes that the relays will see the fault resistor as resistive and inductive impedance due to this phase displacement.

At the line end that is exporting the load, the measured reactance is reduced, the phasor (I2/I1) RF is rotated downwards (Figure 5). At the line end that is importing load, the measured reactance is increased, the phasor (I2/I1) RF is rotated upwards. The smaller the phase displacement between the currents I2 and I1 is, the smaller the influence on the measured reactance will be. In the case of an unloaded line, the EMFs and the currents at both ends are in phase. This assumed that the angles of the fault impedance loop are equal on both sides of the fault, which is on transmission lines normally fulfilled. On faults without ground, the fault impedance will be measured only with an additional resistive part what will not effect the result of the fault locator.

On fault involving ground the method of the zero sequence compensation can effect the reactance calculation, and therefore the fault locator accuracy. By using zero sequence compensation methods which compensate the loop reactance and the loop resistance separately, a poorly ohmic fault resistance on an unloaded line will not cause a calculation error for the reactance. If a complex zero sequence compensation factor is used, the fault resistance is seen as a complex impedance and the reactance calculation which is important for the fault location will be influenced. The compensation using a complex zero sequence compensation factor is only correct for metallic faults.

The effect of the fixed resistance on the reactance measurement may be compensated to a degree with the single-ended fault locator based on certain assumptions.

3. Tower geometry and transposition of the conductors

The geometry of the overhead line towers as well as the phase conductor transposition technique may introduce impedance measuring errors of up to 10% /1/. Extra high voltage lines in transmission networks are often symmetrically transposed with 3 sections. In total, the same impedance for each phase is then approximately achieved for the whole line length. This influencing factor on the accuracy is in this case kept within an acceptable range. In HV systems however, non-transposed lines may be found on short line lengths due to cost constraints.

4. Fault resistance in conjunction with two ended in-feed and load flow

Transmission of load across long transmission lines results in a phase displacement between the voltages V1 and V2 at the two line ends (Figure 5).

In the event of a short circuit, the EMFs (Figure 5) feeding onto the fault will therefore have different phase angles. In a first approximation, the short circuit currents from the two ends are also displaced by this angle. The short circuit current flowing from the two line ends

Michael Claus was born in Wuerz-

burg Germany in

1960. He graduated

from the University

of Hannover with a

master in Electrical

Engineering. He

joint the Siemens

AG in 1988 as a de-

velopment engineer

in Berlin Germany.

In 1991 he moved

to the product

management group

for protection

relays in Nuernberg

Germany. He is the

product manager

for the world wide

Siemens distance

relay business.

2 Infeed from both ends 3 2 Double circuit transmission line

4At the line end the measured reactance is reduced and RF is rotated downwards

A new approach for fault locator is developed for relays with a communication link between each other.

IB

VA VB

IA

R

X

ZL1

VARC / ISC1

1 + K0

IAIA + IB -a =

42an

alys

is

PAC.SPRING.2008

Some solutions require setting the source impedance parameter. This can however not be considered as a constant in most cases, so that this technique is not recommendable. Other principles are based on delta quantities; these utilise the load conditions prior to the short circuit. The results are however only correct if the system topology and the load current do not change during the short circuit condition. This also does not always apply. Other solutions include a load compensation for single phase to ground faults. This technique assumes that the ratio of X0/R0 – and therefore the angle of the zero sequence impedance- to the left of the fault location is the same as the ratio X0/R0 to the right of the fault location. In EHV systems this is often the case. Close to transformers this assumption will however also result in inaccurate result from the fault locator.

Fault locator using measured values from both line ends

Direct digital communication between relays not only facilitates the exchange of protection data, but can also

introduce a significant improvement of the fault location. The advantages of the “two ended” fault locator are:

The fault location of resistive fault is, independent of the load current and line length accurate.

The algorithm only utilises the positive and negative sequence impedance. The zero sequence impedance is no longer required for the fault location calculation in the event of ground faults.

The influence of inductive coupling from parallel feeders may be neglected.

Non-symmetries due to the absence of line transposition and the combination of different tower geometries may be compensated for.

Selection of the measuring data window For accurate fault location computation the currents

and voltages must exhibit as steady a state as possible. The selected data window may therefore not contain any abrupt changes due to fault condition changes or switching. For the fault location computation, a data window containing at least one but not more than three cycles of sampled values is used. The data window selection is carried out automatically by the algorithm. In the event of system disturbances that cause tripping by the device, the data window is positioned around the instant of the trip command. It ends shortly after the circuit breaker opens, immediately prior to interruption of the current. The start of the current and voltage data window is positioned such that the length of the data window is preferably three cycles without any abrupt changes of the current wave form. In the event of very short system faults, or short intervals until the fault condition changes, the measured window may be as short as one system, cycle for the

1 Phase shift between the sources voltages and fault currents5

The fault location becomes calculated with the processing of the synchronised current and voltage vectors from both sides.

The financial

returns for

the company

are optimised

by the higher

availability of

the overhead

line due to

shorter down

times and

consequently

the improved

transfer

capacity of the

network.

Fau

lt L

ocat

or

Current waveform Fault inception Breaker open

Relay pickup

Fault inceptionJump A, C

Data window extension

before trip command

Relay tripCB open

Jump B

Jump

Jump

Prefaultcondition

I / A

1.48 1.5 1.52 1.64 1.56 1.58 1.60 1.62 1.64 t/s

43

PAC.SPRING.2008

computation. (Figure 6) Sometimes it is also desirable to indicate impedance measured value and fault locator data when there is only a fault detection by the protection and no trip command. In this case the data window is positioned at the end of the first fault detection data window. The end of the first fault detection data window is either determined by the re-set of the protection fault detection or by a change of the fault type.

Synchronisation of the phasorsThe “two ended” fault locator uses current and voltage

phasors of all three phases from both line ends. The numerical filters are designed so that the fault location calculation is done based on the fundamental component. The current and voltage phasors are provided with a time stamp, the actual system frequency and data window length information is added and then transmitted via the digital communication link to the corresponding device at the other line terminal. Protection device A therefore receives the values from protection device B and vice versa. With the time stamp, system frequency and data window length the phasors can then be synchronised to a common reference. Using the time stamp, the phasors are then checked to see if they belong to the same condition during the system disturbance.

Only if they both refer to an identical interval of the fault will the computation based on the “two ended” method be done.

Two ended fault locator computation with positive and negative sequence values

The here presented two ended fault location is based on the principle that the voltage decays along the line up to

2 Positioning of the data window after trip by protection

6

the fault location. By means of the currents and voltages measured at one line end, the voltage along the line may be calculated using an RLC line model. If the cause of the voltage is now calculated from both line ends, a fault location may be indicated at the location where both voltages have the same value. In Figure 7 this is given by the intersection of the two curves.

To achieve high accuracy also for long overhead lines and cable sections, the voltage calculation is done based on the homogenous line impedance. The relationship of voltages and currents is given by the hyperbolic function

( ) ( ) ( )xIZxVxV mm ⋅⋅−⋅⋅= gg sinhcosh

whereby: ( )xV voltage at the position x

mV , mI measured value at the corresponding line end x distance from the beginning of the line g propagation constant of the line

The location of the fault can be found much faster due to the increased precision of the fault location output. The time that the feeder is out of service is reduced.

Not influenced by inaccurate ground impedance

compensation factors (XG/XL, RG/RL, k0)

Not influenced by fault resistance on long

heavily loaded lines.

Negligible influence by parallel lines.

Reduced influence due to non-symmetry of

non-transposed lines.

The 4 decisive advantages of this “two ended” method are:

RFVA

R' X' R' X'

C'VB

C'

IA

x yVRF

VA

VA(x) VB(y)

VB

IB

CA B

dA

d

dA dA

C

B

A

d B

A

dC

Non - symmetrical Symmetrical

Line impedance Faulr resistance Voltage Phase conductor

by Dr. Juergen Holbach and Michael Claus, Siemens PT&D, USA

44an

alys

is

PAC.SPRING.2008

( ) ''' CjLjR wwg ⋅+=

Z characteristic impedance of the line

'''

CjLjRZ

ww+

=

At the fault location, the voltages calculated from both ends of the line must be the same.The set of non-linear equations is solved by determining the smallest voltage difference: ( ) ( ) ( )xVxVx rl −⋅=e whereby:

( )xe error voltage (ideally equals zero)( )xV l course of the voltage calculated from the left hand

line terminal ( )xV r course of the voltage calculated from the right hand

line terminal Using proven mathematical techniques the fault

location can be determined by means of the sum of the least squares in the symmetrical component system (least-square’ estimation according to Clarke-Transformation)/2/.

The measuring technique contains several plausibility checks. They are:

Faulty or missing communication telegrams are detected and eliminated

Measured values that deviate extensively from the sinusoidal wave form are detected and not used for the fault location computation. A CT saturation detector additionally ensures that no gross errors in the fault locator are indicated.

Short circuit locations outside the protected feeder can by principle not be calculated by the two ended technique.

Multiple ground faults at different locations on the protected feeder can by definition also not be calculated with the two ended method.

Only when the measured results are plausible, will the two ended fault locator indicate a result. To provide the user with some assistance in locating the fault, an indication based on the single ended impedance measuring technique which is similar to the distance protection measurement, is provided.

Non-symmetrical overhead linesIn connection with the fault location calculation it is

often neglected to consider that the individual conductors of the three phase system are not spaced equally with respect to each other and ground. It is generally assumed that the impedance in all three phases is the same. By neglecting the existing physical non-symmetry of the conductors, the fault locator result will in practice vary, depending on the faulted phase. Ideally, the non-symmetrical inductive coupling between the three phases should be considered in the fault location algorithm. Setting all six coupling impedances would however be very complicated and not practical for the user.

In the two ended fault locator there is therefore a function that allows for the non-symmetry of the impedances of a non-transposed overhead line. When commissioning the fault locator, the central conductor must be defined.

Particularly good results are obtained with tower geometries having horizontal or vertical conductor spacing. In the following diagram the “central conductor is Phase B. If the conductors are properly transposed (refer to 3) no central conductor is defined.

1 Voltage along the line from both sides

7 1 Conductor arrangement on HV towers

8

The fault

locator

provides the

user with

substantial

advantages.

Fau

lt L

ocat

or

46

PAC.SPRING.2008

IEC

618

50E

ngi

nee

rin

g

communication services GOOSE and SMV (Sampled Values) allow new substation functionality or existing functionality with less engineering effort and higher reliability, however introduce multiple sinks for certain signals, which might be concerned by a change at the signal source, as illustrated in Figure 1.

IEC 61850 object types and data identification

IEC 61850-7 introduces IED and communication modelling concepts, and standardized data semantics by standardized names. However, the concrete instance names are additionally dependent on the physical and logical structuring of the data and therefore not a priori stable when replacing IEDs or changing the architecture. What is long term stable (as least as long as the switch yard itself), is the functional meaning of the data in relation to the switch yard respective the power delivery process. Further the substation automation functionality related to the switchyard is normally long term stable, although extensions are not excluded. Therefore IEC 61850-6 introduces a second way of identifying the same data, namely by functional designations as defined in IEC 61346.

IED related objects and their identifications

IEC 61850 as a communication standard in first line addresses data identification at communication level, i.e. at interface level between a server or publisher IED and the data receivers (clients, subscribers). To make this naming independent from the physical structure, the concept of a logical device (LD) is introduced as a management unit for functional parts. Figure 2 shows the resulting internal structure of an IED.

The communication function uses IED access points to connect clients with servers. In principle each logical node can be a client to other logical nodes on some server. IEDs which only receive data, like the OPC server AA1KA1 in Figure 1, can also be pure clients without a server.

To reach the goal of having standardized semantics, the DATA names as well as the names of DATA attributes are completely standardized. Also the semantic of the logical nodes is standardized by means of a logical node class, which is part of the logical node instance name. A real system needs instances of logical node classes, which are associated to different parts of the switch gear; therefore the LN instance

Usage of namesNames are used at system

engineering time to establish relations between the different parts of the system: Relations between the switch yard (primary system) and the IED signals (secondary system), and data flow between IEDs for communication engineering respective online communication association establishment. A name change at a data source therefore leads to reengineering of all IEDs connected to the changed one respective replaced one. In former master slave architectures all data flowed between the bay level IEDs and one single central place, only the IED to be replaced and the central IED were concerned. For IEC 61850 however already for availability reasons several station level IEDs might be connected to the same bay level IEDs, and the new

Designing IEC 61850 systems for maintenance, retrofit and extension

The goal of IEC 61850 is to support arbitrary system configurations with centralized or decentralized architecture. The choice of a specific system architecture is beneath pure technical aspects determined by the existing products and proven solutions. As technology advances, other kinds of architectures may become usable and cost optimal, which lead to a different amount of IEDs and a different internal structure of them, which is reflected in the IED related identification of data. On the other hand, low effort long term maintenance needs identical names for identical objects. But even at the replacement of an IED by a functional equivalent IED from another manufacturer a different internal structuring and naming is most likely.

Wolfgang Wimmer works for ABB Switzerland in Baden. He

is principle engineer in the development of substation auto-

mation systems. He has a M. Sc. degree as well as a Ph.D. in

Computer Science from the University of Hamburg. After some

years developing Computer networks at the German Electron

Synchroton DESY in Hamburg he changed to ABB (former BBC)

for development of train control systems, later Network Con-

trol Systems. He has more than 20 years experience with deve-

lopment of substation automation systems. He is a member of

IEC TC57 WG 19 and WG 10, and editor of IEC 61850-6.

by Dr. Wolfgang Wimmer, ABB, Switzerland

InterlockInterlockInterlock

Color code:

PositionsPositions

GOOSE Unbuffered

Interlock

StatUrg

StatUrg

StatUrg

StatUrgC1 StatUrgC1StatUrgM1MeasFlt

AA1KA1OPC ServerP2WA1

P2Y1COM581***GW***

P2KA3Siprotec-7SJ6xxP2WA1

P2KA2C264P2WA1

P2KA1REC 670P2WA1

P2FA1REL 670P2WA1

P2KA4RED 670P2WA1

47

PAC.SPRING.2008

identification has non standardized parts. The logical device name as a manufacturer / organisation related structuring is completely free within some syntactical limits. This is illustrated in table 1 with an example designation for a switch position value within the switch control function: MyControl LD1/Q0CSWI3.Pos.stVal

A product manufacturer typically provides IEDs as products with some predefined functionality, however with no context to the project specific usage. Therefore the LD relative name and some parts of the LN instance identification need to be given by the manufacturer independent of the unknown project, and might be needed after project engineering to associate the project specific data to the project independent preconfiguration of the IED. Therefore it is manufacturer dependent, which parts of the LN instance identification can be adapted specifically for a project.

Although this designation is mainly used for communication establishment, we might call it a ‘product related’ designation in the sense of IEC 61346-1, especially if the IED designation is used as part of the LD name.

From this discussion we see how the physical architecture influences the communication level naming. Table 2 illustrates this with two logical nodes for the control function: the CSWI handling control commands from the operators and the XCBR executing these commands at the circuit breaker. The architectures referenced in the table are illustrated in Figure 5.

Consequence: different physical architectures by grouping on IEDs as well as different organisational structures by means of logical devices lead to different names, even if an IED and its tool supports free naming for the non standardized parts. And the free naming is not mandatory according to IEC 61850, and naturally introduces additional engineering and testing effort – especially at LN instance level.

Function related objects and identifications

According to IEC 61346 the functional designation is at least as important for operation of a process as the product related naming for maintenance. IEC 61850-6 therefore introduces application related names of data by typically following the functions of the switch yard, however allowing additionally (with

Edition 2 practically at all places) functions which are not directly switch yard related, like protection, control and automation functions, but also supervision functions outside the substation function itself like fire supervision, or functions belonging to power generation. The functional names are completely project / customer specific within the structural restrictions given by IEC 61346-1. The transition object, i.e. the place where product related name and function / application related name matches the same

Usage of application oriented functional names in parallel to

maintenance related IED names

with automatic translation via

SCL files, enhances long term system

maintainability

For

interlocking

reasons, the

controllers

exchange

GOOSE

messages.

The

replacement

of IED P2KA1,

influences

3 other IEDs.

The four

controllers in

different bays

are sending

reports to the

station level

IEDs.

1 Data flow between IEDs in the substation Example of a small system with an OPC server & a gateway as station level IEDs

Figure 1

an example

of a small

system

Substation AA1

Voltage level E1 at 110kV

Bay Q3 Equipment QB1 : DIS

XSWI, Name /XSWI of Type m_XSWI

CSWI, Name /CSWI of Type E3_CSWI

CILO, Name /CILO of Type m_CILO

Equipment QA1 : CBR

XCBR, Name /XCBR of Type E_XCBR

CSWI, Name Q3QA1/CSWI of Type E3_CSWI

CILO, Name Q3QA1/CILO of Type m_CILO

Equipment BE5 : VTR

Function F1 : Protection

PTRC, Name /PTRC of Type E3_PTRC

PSCH, Name /PSCH of Type E3_PSCH

PTEF, Name /PTEF of Type m_PTEF

Subfunction Z1 : Distance zone 1

PDIS, Name /PDIS1 of Type E3_PDIS

Subfunction Z2 : Distance zone 2

PDIS, Name /PDIS2 of Type E3_PDIS

Subfunction Z3 : Distance zone 3

PDIS, Name /PDIS3 of Type E3_PDIS

Subfunction Z1B :

PDIS, Name /BPDIS1 of Type E3_PDIS

Function R1 : ProtRelated

RREC, Name /RREC of Type E3_RREC

RFLO, Name /RFLO of Type E_RFLO

Function M1 : Measurement

MMXU, Name /MMXU of Type E3_MMXU

Process bus access point (can be same as above)

Client associations

Inter bay bus Access point1 logical, several physical

Client association

IEDServer

LN

DO

LN

DO

Logical DeviceLogical Device

LN

DODO

LN

DO

I / O

The server access point allows

access to data structured as

follows: logical devices contain

logical nodes (LN) containing

DATA respective data objects

(DO). Logical nodes on other IEDs

can access the data as clients

IEC

618

5048

PAC.SPRING.2008

En

gin

eeri

ng

object, is the logical node instance. From here on all DATA and attribute names are completely semantically defined in IEC 61850. If we look into the functional names of figure 3 for the same control function handled by the IED related names of table 2, these are:

AA1E1Q3QA1CSWI.Pos AA1E1Q3QA1XCBR.Pos The protection related name of

the operation of distance protection for Zone 1 is:

AA1E1Q3F1Z1PDIS.Op All these names are completely

independent from the distribution of logical nodes and logical devices to IEDs, and also from the LD and LN instance names.

A complete SCL file for a substation automation system, called an SCD file, includes the functional name, the IED related name, the communication related (LD) name, and the relations between them – thus serving as a data base for translation between the different designations for the same LN respective DATA object. This is shown in Figure 4 for the above example, illustrating the independence of the functional name from the IED related name up to the point where IEC 61850 provides complete semantic standardization.

Communication engineeringIEC 61850 MMS based services

allow an interactive browsing of the IED data model to retrieve all communication related names. Due to the unique LD name these can be translated into IED related names as well as functional names by means of the SCD file. However, normally operational traffic is based on preconfigured data flow for services allowing spontaneous sending. These are typically:

Reporting service for status update and time stamped events to station level IEDs like HMI, or gateways to network control centres.

GOOSE real time service for real time functions typically between bay level IEDs, or down to process level IEDs, e.g. interlocking related data or protection trips and blockings.

SMV services, if analogue samples are needed directly from the process, e.g. for protect ion, synchrocheck and measurement functions.

To evaluate the importance of the DATA names for these services, we have to look a bit into their definition:

All services are configured by means of a data set, defining the

IEC 61850

MMS based

services allow

interactive

browsing of

the IED data

model.

2 IED related object model structure

3 Example of a function hierarchy

Functional name:

AA1E1Q3QA1CSWI.Pos.stVal

Substation: AA1

IED related name:

Ctrl9LD1/QA1CSWI 1.Pos.stVal

Voltage level: E1

Bay: Q3

Switch: QA1

LN (class) : CSWI

Attribute: stVal

LD: LD1

IED: Ctrl9

DATA: Pos

LN: QA1CSWI 1

The structuring and naming

of the functional identifi-

cation (left) down to the

LN class are completely

independent from the IED

related name (right)

49

PAC.SPRING.2008

data to be spontaneously sent, and a control block, defining when and how it shall be sent, as illustrated in Figure 6.

The reporting service only sends the changed data values. A bit pattern in each report identifies the place of the data set to which the sent data values belong.

For GOOSE and SMV services always all values of the whole data set are sent. The order of values in the message corresponds to the order of the data items in the data set definition.

This means, that essentially the values sent on the wire do not contain any of the names considered earlier, just the relation between the sent values and their place in the data set definition. For correct message interpretation the receivers only have to know, to which data set the message belongs, and how this data set looks like. For reports this can be established dynamically by means of the browsing services or data set creation services, however also by static configuration with a common SCD file as base. The relation between the online message and the data set definition then is established as follows:

Reports are MMS based and MMS a ssociat ions must be

dynamically established. A report client either builds its own data sets dynamically (if the servers support this), or uses preconfigured data sets. If he relies on preconfigured data sets, he can check at start-up the control block revision number on any discrepancies between static definition and actual definition on the IED.

GOOSE and SMV messages work according to the subscription principle and are permanently sent. The message contains Ethernet level identifications like Multicast address and application identification (AP P ID), and the d at a set identification in the form <LD name>/<LN Name>.<Data set name>, which allows the subscribers to identify and filter the correct message fitting to the DATA they want to use from their static configuration based on the SCD file. A control block revision number, always sent in the message, allows receivers to detect any discrepancies in data set layout configuration between sender and receivers.

This interpretation of messages relative to a data set definition allows to replace e.g. a GOOSE publisher by any other IED without having to reconfigure the receivers, as long as the new IED.

Contains the data of the old GOOSE message with same data types and same semantics (functional equivalence).

Contains or allows configuring a data set with the same type of data values in the same order and same semantics related to the project as the old IED.

Uses the same Ethernet level addressing (Multicast address, APPID, VLAN).

Has the same full data set name: same LD name (if freely configurable on the IED), same LN name (LLN0 for all GOOSE and SMV messages), the same data set name (mostly configurable at the IED for GOOSE and SMV data sets), and the same configuration revision number (needs free setting by the tool creating the data set, or some tool support for the replacement).

Different physical structures enforce

different IED related data identifications at

IED/LD/LN level

4 Connection of functional and product related naming–example

Ctrl 9

Station level

Bay level

Process level

Ctrl 1

Swg 8 SWg 9

Ctrl 9

Swg 8 SWg 9

Bay controller

+ Process bus

Central controller

+ Process bus

Bay controller

IEC 61850 offers solutions to

minimize the influence of main-

tenance activities at application

level, by introducing in parallel

to the IED related identification

a function oriented identifica-

tion of data according to the

concepts of IEC 61346.

IEC

618

5050

PAC.SPRING.2008

En

gin

eeri

ng

This means that the replacing IED has beneath the requirements on compatible semantics and data types to fulfil some engineering related requirements, which are not mandatory according to IEC 61850. Further it should be considered that errors at the reconfiguration of the data set when keeping the old revision number and data set identification can be safety critical, because the receivers do not demand to be newly configured. So, a good tool support or testing in a simulated environment is recommended.

The problem of binding GOOSE or SMV receivers to the data set layout does not appear for reporting clients, because they can perform this binding dynamically. However, if the names have changed, the binding to the functional semantics, especially binding of LN instances to instances of switch yard equipment and functions, is still a problem. One means to solve this binding to the application function is to re-establishing the link between functional names and IED related names also for the new IED(s). This is

supported in IEC 61850 better than in other protocols in so far, as this binding is done on the level of logical nodes instead of signals, and will in all cases, where application specific LNs are used (e.g. no GAPC and no GGIO), reduce to a selection of LN instances with the same LN class, thus minimizing the amount of work as well as that of errors.

For good implementations of station level clients, which internally work with the functional names as defined above, it is then sufficient to reload them at driver level with the SCD file resulting from this re-mapping of LN instances.

E v e n b e t t e r c l i e n t implementations allow to do this reload per IED e.g. when communication with the (new) IED is (re-) established. In any case, the probability of errors is restricted to the remapped IED, and this

Use functional names as a key

between old and new

configurations

5 Different architectures

Name differences caused by architectureTable 2

Architecture LD Name LN Name DATA Name Remark

Single bay controller

Ctr19LD1Ctr19LD1

Q0CSWI1Q0XCBR1

PosPos LNs located in same LD

Process bus from bay controller to circuit breaker

interface

Ctr19LD1SWg8LD1

Q0CSWI1QA1XCBR4

PosPos

LD (IED) name at switch interface IED must be different to name in bay controller; LN

instance names are manufacturer specific.

Central controller with process bus to circuit breaker

interface

Ctrl11LD9SWg8LD1

Q0CSWI1QA1XCBR4

PosPos

Free LD naming would allow using centrally the same LD names as de-centrally – if the

central LD structure is the same.

Degree of name standardizationTable 1

IED structurelevel

Degree of standardization Exampledesignation

Stan-dardized

Predefined na-me semantic

Logical device LD Syntactical (61850-7-2) MyControlLD1 --- ---

100 Kb/S Partly: LN class (61850-7-4) Q0CSWI3 CSWI Switch control

200 Kb/S Full: DATA name (61850-7-4) Pos Pos Switch position

Attribute Full: Attribute name (61850-7-3) stVal stVal Status value

For maintenance it is recommended to choose an IED related logical device name, structured as IED name - LD relative name

defined by data sets and control blocks (CB)

DO

LN

DO

LN

Logical Device

DO

LN

Logical Device

IED

Data Set

GOOSE or Report messages

triggers

CB

51

PAC.SPRING.2008

probability is quite low, because the remapping is performed on the relatively high level of LN instances, supported in most cases by the needed LN class. It should however be considered that the new IED should contain at least the same DATA per remapped LN instance as needed by the application.

Impact on engineering and used products

The follow ing point s are important to minimize the efforts in case of SA system retrofit:

Use functional naming for system engineering and the IED related names, so that the SCD file provides a translation between them in a standardized format.

Use functional naming at application level, i.e. within application functions. Let the (MMS based) communication drivers translate the IED names into functional names by means of SCD file(s). In case of (station level) clients which do not support this, use a tool to create the new configuration from the SCD file, by using the functional name as common key between old and new configuration.

The safety of this approach can be supported by a system tool which supports the IED replacement at the functional structure on LN level, with a check of the same respective correct LN classes.

As we have seen, the replacement of GOOSE servers without having to reconfigure all GOOSE receivers needs some optional features from the IED respective its tool:

Support free LD naming Support free data set naming, at

least for GOOSE and SMV data sets Support free (guided) setting of

GOOSE confRevTo make this procedure safer,

the tool should support remapping the new IED to the functional names and, after this remapping, automatically (re-)create the GOOSE / SMV data sets with identical layout and name, set the LD name property identical and take over all ‘old’ addresses.

Unfortunately, all these features do not help for the GOOSE / SMV case, if a changed architecture leads to another logical device structure, so that the requirement on uniqueness of the LD name forbids the proposed LD renaming, or if due to a new physical structure the GOOSE messages have to be split onto different IEDs.

Some impact on system modelling principles

A relatively safe tool-supported binding of the LN instances of the new IED to the functional names by using the old IED’s binding as template is only assured, if GGIO and GAPC LN classes are avoided as far as possible. This is also in the sense of IEC 61850, which demands using a fitting LN class wherever one is defined. Here also some improvements of manufacturer IED tools might help, which allow replacing a GGIO by a more appropriate LN class at IED (pre-) engineering time.

However, if the old structuring into logical devices does not fit to the new structuring, this does not help. Therefore, already at the initial system design, the logical device structure in relation to the used GOOSE and SMV messages should be set up to support the most distributed structure which is intended to be used during the switch yard life time. Further, GOOSE and SMV data sets should not reference data outside the LD in which they are defined – else these may later reside on different IEDs, and therefore force a redefinition of the data sets with appropriate re-engineering of the receivers.

The general concept of a maximal distributed system, even if it is implemented centrally, also helps in having a common behaviour of distributed and central systems concerning functionally connected logical nodes, because it makes the functional behaviour independent from the fact if internal functional connections between the LN implementation are used or external

explicit communication connections. This has also been considered at the more detailed definitions of IEC 61850 Edition 2 for the influence of the test and block quality of incoming signals, and should also be used when implementing test and block modes on internally connected logical nodes.

If these additional system structuring rules are considered, then the consequent usage of functional naming for application related functions in parallel to the usage of product related naming for automation system maintenance, as foreseen in IEC61850-6, supports easy retrofit and system extension with minimum engineering, modification and (re-)testing effort even if the underlying physical architecture is changed or IEDs of a different type or a different manufacturer are used.

Designing systems for the maximal

ever intended physical distribution,

eases future retrofit

6 Communication model

Communi-

cation model

with data sets

and control

blocks

Iana A. Apostolova J.D.

PAC.SPRING.2008

Lega

l Iss

ues

Cla

ss A

ctio

n L

awsu

its

53

As we will consistently reestablish in these editorials, there are many legal concerns which do, and will continue to, have an increasingly significant impact on the protec­tion and control world. This issue however, focuses on the manner in which these legal matters are brought to the forefront, the most considerable of which, is the class action lawsuit.

Whenever a blackout or other ma­jor power disturbance occurs, mil­lions of consumers are affected, to varying levels on “inconvenience.” While an individual consumer may loose the ability to complete his midterm paper, to a hospital, an outage of even a couple of hours can have devastating consequen­ces. Clearly, in such circumstances large institutions and corporation possess the legal resources neces­sary to assert their legal rights, and demand answers and more importantly, compensation, from the relevant utility that they deem at fault. However it is unlikely that too many average consumers, would regard themselves irked enough to file an individual claim versus a large, and well legally pro­tected utility. At least so would be the case, if not for the powerful le­gal tool of the class action lawsuit. In the words of the U.S. Supreme

A c l a s s a c t i o n l a w s u i t i s a procedural device that permits the litigation of multiple claims in a single proceeding.

larger group.” Black’s Law Dictio­nary, 7th Edition. Federal proce­dure has several requirements for maintaining a class action: (1) the class must be so large that indivi­dual suits would be impracticable, (2) there must be legal or factual questions common to the class, (3) the claims or defenses of the repre­sentative parties must be typical of the class, and (4) the re presentative parties must adequately protect the interests of the class.

This definition sheds light on the fact that the class action lawsuit has become so popular in recent years with power consumers. It is evident that it would be im­practicable for such a multitude of customers to file individual suits, when there are so many common questions of both law and fact at the core of their grievance.

The increasing phenomenon of the class action lawsuit should be a source of notable concern for utili­ties, for it affords all its individual members the ability to pool their strength and assets together into a lawsuit, which once resolved, could require the affected utility to pay compensations worth mil­lions, versus the comparatively modest number which an indivi­dual suit would produce.

Court, “the class action was an invention of equity… mothered by the practical necessity of pro­viding a procedural device so that mere numbers would not disable large groups of individuals, united in interest, from enforcing their equitable rights nor grant them immunity from their equitable wrongs. Montgomery Ward & Co. v. Langer, 168 F.2d 182, 187 (8th Cir. 1948). It is this “procedural device” that gives all consumers, large and small alike, the ability to bind together, and wage their own personal battle, for accountability and reparations.

A class action lawsuit is literally defined as “a lawsuit in which a single person or a small group of people represents the interests of a

BiographyIana graduated

from UCLA in

2001 with a

major in Political

Science. In 2005

she was awarded

the degree of

Juris Doctor,

from Loyolla Law

School.

During her

studies, Iana

worked for Soft

Power Int., where

she became well

aquainted with

the engineering

world. She

furthered

her business

knowledge

working for

Insurance

Marketing Inc.

Upon graduating

from Law School,

Iana joined the

Criminal Defence

field, where she

has devoted her

talents to fight

for her clients.

Iana is currently

working on her

MBA from Ashford

University.

PossibleLegal Concerns

80

60

40

20

0

-80

-20

-40

-60

25 50 75 100Time [ms]

Curre

nt [A

]

80

60

40

20

0

-20

-40

-60

-80

Cur

rent

[A

]

Time (ms)

0 25 50 75 100 I I I I

54

PAC.SPRING.2008

by Demetrios Tziouvaras, Schweitzer Engineering Laboratories, Inc.,USASy

srem

An

alys

is

EMT

P

STEADY-STATE APPLICATIONSPower system operations can

cause unbalanced currents and voltages in the network that could impact the operation of protective relays, e.g., during a single-phase trip, unequal gap flashover of series capacitors, or when a three-phase transformer bank consists of different single-phase units. These operating conditions cannot be analyzed using conventional load-flow programs but can be easily studied using steady-state EMTP simulations and demonstrate the benefits of applying EMTP for power system protection applications.

Conventional short-circuit and load-flow programs assume

EMTP Applications FOR POWER SYSTEM PROTECTION

The EMTP can supplement conventional fault studies and hand calculations to improve the understanding of power system phenomena and to assist in proper protection applications.

A protection engineer may determine extreme conditions of steady state fundamental frequency unbalances or harmonic distortion that will be faced by a protection system.

Biographical SketchDemetrios Tziouvaras was born in Mona-

hiti, Grevena, Greece. He holds a Masters

Degree in Electrical Engineering from

Santa Clara University, California, USA.

From 1980 to 1998 he worked for Pacific

Gas and Electric Co., where he held

various positions in the System Protection

Department including Principal Protec-

tion Engineer responsible for protection

design standards, application of new

technologies, substation automation,

relay settings, and analysis of relay opera-

tions and system disturbances. He joined

the Research Engineering Department

of Schweitzer Engineering Laboratories,

Inc. in 1998 where he is involved in digital

relay algorithm development and electro-

magnetic transient simulations.

Mr. Tziouvaras is a senior IEEE member and

member of the Power System Relaying

Committee. He is a member of CIGRE

and the convenor of CIGRE SC B5.15 on

“Modern Distance Protection Functions

and Applications.”

He is the author of more than 35 IEEE

and Protective Relay Conference papers,

holds three patents in the area of power

system protection and has more pending.

He has taught seminars in Protective Re-

laying, Digital Relaying, and EMTP at the

University of Illinois at Urbana-Champaign,

the California Polytechnic Institute in San

Luis Obispo, IEEE PES, and elsewhere. He

served as the chairman of an IEEE PSRC

working group that developed an IEEE PES

tutorial on “EMTP Applications to Power

System Protection”

Comparison Comparison of a laboratory and an EMTP simulated CT saturation test

1

55

PAC.SPRING.2008

Series capacitor gap flashing during a fault is a special case of a multiple unbalance. Unbalanced gap flashover may occur as a result of a short circuit, or unbalanced bypass may occur as a result of control or bypass equipment problems. EMTP can calculate steady-state unbalance currents and voltages resulting from such unbalanced operation. Knowledge of these quantities can assist in proper protective relay application and settings. Simultaneous or cross-country faults are difficult to analyze with conventional short-circuit programs that use sequence components for analysis but are easily handled by EMTP simulations.

U n d e r s o m e co n d i t i o n s , unbalances are deliber ately introduced into a network to address special problems. For example, failure of a large single-phase transformer may necessitate its replacement with another single-phase transformer having different MVA capability and different leakage reactances. EMTP simulations can be used in such a situation to determine the steady-state unbalances resulting from load flowing through the unbalanced transformer impedances. The simulations would reveal the

level of system unbalance and the circulating current in the transformer bank tertiary winding. Relay engineers can use the results of the EMTP steady-state simulations to determine the effect on transmission line protection and the required settings for transformer tertiary overload protection.

In addition to unbalanced analysis, steady-st ate EM T P solutions help to study the effect of non-fundamental frequencies on relays. For instance, the system response at a variety of frequencies generated by a multifrequency injection may be used to test for the presence of system resonances. Such information will help determine the importance of harmonic rejection in relays in particular applications.

a balanced power system. The assumption of a balanced system is usually adequate under normal operating conditions. In cases where network unbalances exist under normal conditions, conventional programs may not be able to determine the magnitude of normal unbalances. EMTP steady-state solutions are performed in the phase domain, not using sequence components, thereby easily solving networks with nonsymmetrical phase impedances. The EMTP steady-state solution may be used to help quantify the extent of normal unbalances to assist in relay applications.

Open conductors create series unbalances that are not normal conditions, and relays may be expected to protect against them. However, the resulting system unbalances may be significantly less than unbalances resulting from short circuits. In fact, the unbalance currents and voltages are heavily dependent on the magnitude of load currents. EMTP steady-state solutions can readily determine voltages and current measured by relays under such conditions. Cases of interest are: single-phase tripping; 1 phase of a disconnect switch open.

Calculated distance values Calculated distance m values with normal and saturated currents

2

0

0.25

0.5

0.75

1

0 0.05 0.1 0.15 0.2 0.25 0.3

Cal

cula

ted

m

Time (s)

Nonsaturated

Saturated5

2.5

0

-2.5

-5Cal

cula

ted

m

Time (s)

0 0. 05 0.1 0.15 0.2 0.25 I I I I I

Saturated

Nonsaturated

The calculated distance to the fault m

value corresponding to a normal fault

current settles to 0.33 as expected. For

a saturated phase current (Fig. 2), the

calculated distance m value crosses the

unity line with a half-cycle delay and

settles around 0.45 because the current

remains in a saturated state.

EMTP is a valuable tool for analyzing

the transient and dynamic behavior of

power systems.

56

PAC.SPRING.2008

Sysr

em A

nal

ysis

EMT

PPower line carrier frequencies propagate in several modes on a multiphase transmission system. Study of these propagation modes is complicated by discontinuities in the transmission circuit, such as transpositions and overhead-to-underground interfaces. At high frequencies, such as those of power line carrier, EMTP steady-state solutions can be used to study the effects of line transpositions and discontinuities on wave propagation.

Transient ApplicationsSeveral transient applications

are discussed here to demonstrate the benefits of EMTP applications in the field of system protection engineering.

EMTP is a very powerful tool in the study of transient conditions. EM T P aids si gnific antly in protective relay applications since protective relays operate during transient conditions. Traditional relay application has considered fault conditions to be temporary steady-st ate condit ions that can be studied by fundamental frequenc y steady-st ate fault studies. Conventional short-circuit studies exclude some important phenomena, and some conditions are not even caused by short circuits. Additionally, the duration of a transient EMTP study is variable. The period of signals of interest may vary from microseconds to tens of seconds.

Series capacitors in transmission lines often present challenges to protection systems. Depending on the size and location of the capacitor bank and the overvoltage protective equipment such as spark gaps or metal oxide varistors (MOVs), the operating and polarizing signals presented to transmission line protection can be very unusual. C o nve n t i o n a l s h o r t- c i rc u i t programs often have difficulty in calculating fault quantities because of the non-linear performance of the series capacitor overvoltage protection gaps or MOVs. Further,

the interaction of the series capacitors and power system introduce off-nominal frequencies that can affect protective relays. When the capacitor is switched into or out of the transmission line, system oscillations arise that should be considered for line protection application and setting.

Relay response to evolving faults is sometimes uncertain. This is especially applicable to protection systems, which must determine the type of fault before measuring the faulted loop impedance (such as switched distance protection schemes). The uncertainty arises because of the wide variety of rapidly changing conditions that may potentially confuse a protection system, which is trying to determine the type of fault. EMTP provides a convenient way to generate test signals to physically test a relay's response to such faults.

Traveling wave high-speed transmission line protection systems do not use the fundamental frequency components. They use higher frequency signals to determine the direction or type of fault. EMTP-generated signals are essential for application studies, testing and settings of such relays.

Some power system effects simply cannot be investigated by any other means than a transient analysis program. Single-phase switching is one area where EMTP has been widely applied. An important problem in such cases is extinction of the secondary arc after the faulted phase is opened at the line terminals. This secondary arc may be maintained by capacitive and inductive coupling with adjacent energized phases. Special four-reactor bank applications have been designed and widely applied to minimize the duration of secondary arc. The presence of these reactors and the secondary arc can have significant effects on transmission line relaying. EMTP has been used to study the secondary arc extinction characteristics and protective relay

response to such transients. To perform single-phase tripping, transmission line protection relays are required to determine the faulted phase. Numerous faulted phase selection schemes have been designed. The effect of heavy load and possible high fault resistance during single line-to-ground faults remain challenging applications. EMTP has been widely used to test relay response to such challenges.

High-speed automatic reclosing is frequently applied to maintain the integrity of a transmission system after a short circuit. Voltage detectors are sometimes used to supervise such reclosing to ensure the remote line terminal has opened before reclosing occurs. The oscillatory decay of the trapped charge remaining on the line may cause problems to voltage detectors used for such supervision. EMTP offers a convenient way to test voltage detector’s response to such oscillatory decay. The dynamic response of the power system to faults and automatic reclosing has an important effect on relay performance. This is particularly important on protection systems designed to trip or block on OOS conditions or to respond to rate of change of certain parameters. EMTP may be used to simulate such conditions to determine protection performance.

The time varying response of rotating machines to changes in system conditions has always caused difficulties in protection application. Induction motors can contribute current to short circuits for a brief time, but such contributions are normally neglected in protection applications. Synchronous motors and generators cont r ibute a varying amount of current to short circuits, depending on the type of

Effectively

using EMTP to

model complex

power system

operating

conditions can

improve the

protection

schemes

and provide

answers

to relay

operations

that otherwise

are difficult to

obtain.

Effectively using EMTP can provide answers to

relay operations.

–5

–2.5

0

2.5

5

0.1 0.15 0.2 0.25 0.3

Cal

cula

ted

m

Time (s)

0 0.05

Saturated

Nonsaturated

–1 –0.5 0 0.5 1 1.5 2 2.5 3

–60

–40

–20

0

20

40

60

Wav

e

–1 –0.5 0 0.5 1 1.5 2 2.5 30

2

4

6

8

10

Mag

nitu

de

Time (cycle)

CVT Output

Ratio Voltage

CVT Transient

Ratio Voltage

5

2.5

0

-2.5

-5

Cal

cula

ted

m

0 0.05 0.1 0.15 0.2 0.25 0.3

Time (s)

5

2.5

0

-2.5

-5Mag

nitu

de

0 -0.05 0 0.5 1.0 1.5 2.0 2.5 3.0

Time (cycle)

I I I I I I

I I I I I I I I

I I I I I I I I

57

PAC.SPRING.2008

Figure 4 a/b:

shows a CVT

transient response

during a line-to-

ground fault.

Figure 3:

shows the

unsaturated and

saturated current

waveforms from

an EMTP simula-

tion of a CT model

for a line fault at

a distance of 33

percent from the

relay location.

Figure 4 a/b:

also shows the

fundamental

frequency mag-

nitude of a CVT

secondary voltage

as compared with

the ideal ratio

voltage.

excitation system and the duration of the period of study. Protection of synchronous motors is normally applied considering response within a cycle or two of the fault initiation, or after a considerable period of time when steady-state fault conditions exist. This type of study leaves a gap in simulation that is readily covered by EMTP simulations of the generator and its excitation system. Synchronous machines could lose synchronism (OOS) with the power system, requiring prompt protective relay action. These OOS conditions are readily simulated by EMTP. The results of such simulations aid in the application of power swing blocking, OOS tripping, or field failure protection applications.

EM T P simulations are not l imit ed to elec t roma gnet ic transients. EMTP can be used to st udy elec t romec hanic al transients. For instance, large thermal turbine-generators have been damaged or destroyed by electromechanical subsynchronous oscillat ions caused by series

Protection engineers are

encouraged to apply the various

capabilities of EMTP to help

them design more robust and

dependable power systems.

Saturated and normal phase currents 3

CVT Transients - waveCVT transients reduce the fundamental voltage magnitude

4a

CVT Transients - magnitude CVT transients reduce the fundamental voltage magnitude

4b

Saturated

Nonsaturated

CVT Output

Ratio Voltage

–1 –0.5 0 0.5 1 1.5 2 2.5 3

–60

–40

–20

0

20

40

60

Wav

e

–1 –0.5 0 0.5 1 1.5 2 2.5 30

2

4

6

8

10

Mag

nitu

de

Time (cycle)

CVT Output

Ratio Voltage

CVT Transient

Ratio Voltage

60

40

20

0

-20

-40

-60

Wav

e

-1 -0.5 0 0.5 1.0 1.5 2.0 2.5 3.0

Time (cycle)

Ratio Voltage

CVT Transient

2000

0

-2000

Mag

nitu

de (M

ag)

0 500 1000 1500 2000 2500 3000

Time (ms)

–0.5 0 0.5 1 1.5 20

0.5

1

1.5

2

2.5X-

Ohm

R-Ohm

Relay Protection Region

Apparent Impedance From CVT Output

Apparent Impedance From Ratio Voltage

2.0

1.5

1.0

0.5

0

X - O

hm

-0.5 0 0.5 1.0 1.5 2.0

58

PAC.SPRING.2008

EMT

PSy

srem

An

alys

is

Figure 6, 7:The waveforms

shown in those

figures are from a

simulated

multi-machine

network.

capacitors on nearby transmission lines. Subsynchronous electrical oscillations can excite mechanical resonances on large thermal turbine generators with sometimes c at a st rophic result s . EM T P simulations have been used to apply protection systems to prevent unit damage by subsynchronous oscillations.

Examples: Simulation of Instrument

Transformer Transients Current and voltage transducers

provide instrument-level signals to protective relays. Protective relay accuracy and performance is directly related to the steady-state and transient performance of the

instrument transformers. Protective relays are designed to operate in a shorter time period than that of the transient disturbance during a system fault. Large instrument transformer transient errors may delay or prevent relay operation. EMTP simulation of instrument transformer transients can be used to study their effect on the performance of relay elements.

S imula t ion of Cur rent Transformer Transients:

CTs can saturate due to large symmetrical fault currents or the prolonged presence of a DC component in the primary fault current. The fidelity of the CT transformation is reasonably good until saturation takes place. Upon

saturation, the CT current delivered to the relays and other instruments deviates in both magnitude and phase angle from the current flowing in the power system. Current transformer transient performance can be easily modeled by EMTP. Transient saturation, steady-state saturation and poor performance, due to low-frequency effects, (including geomagnetic induced currents) can all be simulated.

Figure 1 shows a comparison of recorded laboratory secondary CT waveforms and EMTP simulated secondary CT waveforms. The simulation results are nearly identical to the laboratory tests.

Figure 3 shows the current w avefo r m s f ro m a n E M T P simulation of a CT model for a line fault at a distance of 33 % from the relay location. Figure 2 shows the response of a numerical distance relay to the unsaturated and saturated waveforms shown in Figure 3. The calculated distance to the fault m value corresponding to a normal fault current, settles to 0.33 as expected. For a saturated phase current (Fig. 3), the calculated distance m value crosses the unity line with a half-cycle delay and settles around 0.45 because the current remains in a saturated state.

Capacitive Voltage Transformer (CVT) Transients:

Similar to poor CT performance, CVTs can also cause unexpected protection system performance.

EMTP simulation of out of step phenomena the OOS condition resembles that of a two-machine system

6

Overreach due to CVT transients Two apparent impedance loci of an end-of-line fault, calculated from the ideal ratio voltage and the CVT secondary voltage

5

Apparent Impedance from Ratio Voltage

Apparent Impedance from CVT Output

Relay Protection Region R - Ohm

1000

0

-1000Mag

nitu

de (M

ag)

0 500 1000 1500 2000 2500 3000

Time (ms)

59

PAC.SPRING.2008

Figure 7: The waveforms

shown here

would be impossible

to generate using a

test set while trying

to ramp the volta-

ges, currents, and/or

frequency.

One of the most common causes is a subsidence transient that can grossly distort the secondary signals presented to a relay. (Fig.4a,b) EMTP can simulate CVTs connected to the power system and provide suitable test signals for determining relay performance. In addition to the subsidence transient, CVT response to non-fundamental frequency signals can also be determined. CVT transients reduce the fundamental component of the fault voltage and cause distance relays to calculate a smaller than actual apparent impedance to the fault. (Fig. 4 a,b) Ferroresonance is possible in any system composed of capacitors and iron-core inductances. In a CVT, the interaction of the source capacitance with the tuning reactor inductance and the step-down transformer magnetizing inductance can lead to a ferroresonance oscillation. CVT manufacturers use ferroresonance-suppression circuits (FSCs) to reduce or eliminate ferroresonance conditions. EMTP can be used to simulate ferroresonance conditions in CVTs.

Relay Testing with EMTP Generated Signals

Relay testing in the field has generally involved steady-state tests to determine the integrity of the relay. These tests were performed in the past using variacs, phase shifters, and load boxes, or more recently with modern electronic test equipment. In recent years, more interest has arisen

in testing the relays under transient fault conditions that they will likely encounter while in service.

For many years, model power systems were used for transient tests. Because of the expense, such systems were only available to relay manufacturers and research laboratories. Since digital system analysis techniques are widely available, EMTP or real-time digital simulators are often the tools of choice to generate transient test signals for relay application tests. For troubleshooting tests, digital fault recorder (DFR) or relay-captured event signals may be available to replay using modern electronic test equipment.

EMTP simulations are able to represent a variety of power system conditions in which protection systems must operate reliably. The simulations may include models of the instrument transformers used to convert the signals to relay input levels. Since the EMTP output consists of a file of numbers representing instantaneous values of signals "seen" by a protection system, some hardware is required to convert these numbers to an analogue electrical signal that can be injected into the relay. The format of test files has recently been standardized to simplify exchange between interested parties. This allows test files from actual DFR records or EMTP simulations to be used almost interchangeably.

Test ing of Power-Swing Protection Functions:

The most appropriate test method to verify the relay behavior during stable power swings or OOS (loss of synchronism) conditions is to generate a number of COMTRADE test cases from EMTP simulations and play them back into the relay using modern test equipment. Modern test sets are capable of replaying COMTRADE waveforms captured during power swings by relays and DFRs or generated by EMTP. Using this methodology, one can verify if the relay will perform satisfactorily during stable or unstable power swings.

Figures 6 and 7 demonstrate how different the waveforms are on two transmission lines in the same network during an OOS condition. Testing of power-swing protection functions with traditional relay testing equipment can be very difficult, if not impossible, to perform. The difficulty arises from the inability of older test sets to reproduce the type of waveforms present during power swings.

Out of step waveforms of multimachine power systems The example shows how complex the OOS waveforms can be due to multi-machine mode excitation

7

EMTP is a valuable tool for relay testing

and setting optimization.

6060

PAC.SPRING.2008

the

guru p

asa d

mat

a Technical innovation and developments

are taking place in a very high

pace.

More than 50 years in protection. r

All awards have been very enjoyable, intoxicating and encouraging.

shri

1991

2008

1982

1998

the

guru

PAC.SPRING.2008

Biography Shri Mata Prasad has more than 50

years of experience in the fields of

electric power systems protection,

extra high voltage and high voltage

DC systems, power plants and SVC.

He received his B. Sc. degree in

Electrical Engineering from BHU

Varanasi. He was responsible for

the development of the first 400 kV

system, as well as the first SVC, the

first HVDC bulk power transmission

and the first HVDC asynchronous

link in India.

He has also worked in Sweden, the

UK and France and has been an

active member of many professional

organizations, achieving the status

of Distinguished Member of CIGRE

and Senior Member of IEEE, and a

Fellow of the Indian Academy of

Engineering.

For his accomplishments and

contributions he has received

many national and international

awards, such as the CBIP Golden

Jubilee Award. the CIGRE Technical

Committee Award and the CEA

Silver Jubilee Celebrations Award.

He has authored and presented

more than 115 papers at many

conferences around the world.

I like to read and think about all the questions that we have not answered yet. .

Shri Mata Prasad

62

PAC.SPRING.2008

PAC World: Would you tell us something about the places where you were born and where you grew-up? MP: I was born at Varanasi, UP on 3rd April 1932 and completed High School (Commerce) from Sanatan Dharam High School in 1948, Intermediate (Science) from Banaras Hindu University 1950 and B.Sc., Electrical Engineering from Banaras Hindu University in 1954, in Varanasi.PAC World: Do you think there was something special during your school years that affected your future?MP: I was quite keen to study engineering, especially mechanical engineering, since the day I started school due to my special fascination for machines and mechanical gadgets. Unfortunately, I had to continue my academic education until high school with non-science subjects like commerce, bookkeeping and accounting. However this did not discourage me from pursuing an engineering education. PAC World: Did your family influence your career?MP: I lost my father in 1948 just before my high school examination. The inspirational support I received from my creative mother gave me all the strength to complete my engineering courses - securing first division in all the

four years of my engineering education. I believe, it was God’s wish that none of my close relatives came forward to guide or support me in my efforts and I surrendered to Almighty God to guide me all the way. This proved to be a blessing as I received all the help from HIM and I never felt alone. The strength

of my mother and guidance from Above kept me fully energized to realize my objectives.PAC World: Did you have any special interests while in school?MP: I did have interest in pencil sketching, instrumental music, drama and some games like volleyball, but my special inclination was towards reading everything I could lay my hands on, including novels, stories and mythological/religious masterpieces like Ramayana, Mahabharata and Bhagavad-Gita. The contribution and direct influence from Shri Jaishankar Prasad, a great name in Hindi literature who was a close friend of my father and quite influential. I had time allotted to study my normal course and general literature studies that did not leave me

My family

plays a very

important

role in

my life.

63

PAC.SPRING.2008

time for indoor or outdoor games. I always felt a shortage of available time during my youth and even today I feel that there isn’t enough time and so many things to do.PAC World: How and when did you decide to study electrical engineering?MP: The four year engineering course at BHU consisted of two years for combined study in civil, mechanical and electrical engineering. In the third year, one has to select whether to pursue a mechanical or electrical discipline. As I said earlier, I had a blind infatuation for mechanical engineering however a group of my Electrical Engineering professors, especially Prof PC Dutt, Prof MC Pandey and Principal M Sengupta advised me to choose electrical engineering as they felt that I was more suited for it. Today I must admit that my professors correctly judged my aptitude and I owe everything to them.PAC World: Did you study protection while in university?MP: Yes, I did study basics of Protection relaying covering Generator, Transformer and Transmission Lines and this particular topic fascinated me especially when I had gone through some of the classic relaying schemes described by Lewis and Tippet, Montieth and others published in AIEEE Transactions . I was later exposed to protection philosophy when I joined active service in UP Electricity Department in 1957. PAC World: Did you have any other interests while studying? Sports? Music? Arts?MP: As I said earlier, I did have great interest in music and arts but I could never fulfill my desire to accomplish anything further in this regard. I was very good in pencil sketching of portraits and landscapes. I should have contin-ued in these fields at least after retirement!PAC World: Where did you start your career? Did you work on power system protection from the beginning?MP: From October 1954 to January 1955 I was under training in Rihand Hydro project department and then shifted to field duties - responsible for surveying and construction of 33 kV double circuit lines. After joining the Electricity Department as Assistant Project Engineer in 1957, the first technical job allotted to me was to study the Protection System for Rihand Power Plant and draw specifications for protection of 132 kV lines and substations. Thus, I started my career with Protection and that became my first love. PAC World: Would you describe the most challenging project that you have been involved in?MP: There were scores of challenging jobs entrusted to me and successfully delivered. For example, the interconnection system of the Obra 1000 MW power plant with nine 400 kV lines of length varying from 140 to 400 km. In 1984, I joined NTPC on deputation for the HVDC Projects and also for handling the associated 400 kV lines from power plants and interconnected network. I had the privilege to be actively associated with the first 400 kV Static Var Compensators at Kanpur, the first 2*250 MW

Asynchronous Back-to-Back HVDC Link between Northern and Western Regions, the first 810 KM Long +/- 500 kV Bulk Power HVDC Transmission from the Rihand Power plant to the Dadri HVDC Receiving Station.PAC World: You received several awards for science and technology in your country. Would you describe some of them and why you did receive them? MP: God was very kind to me that I received the following prestigious awards:

CBIP Golden Jubilee award in 1982 for my contribution for successful execution of field tests on 400 KV system

NPSC Award in 1991 for Excellence in Power System Management

“Distinguished Member” of CIGRE (France) Award in 1996 for my contribution in CIGRE Activities in India and abroad

CIGRE Technical Committee Award in 1997 for Outstanding Contribution in SC 14 HVDC & Power Electronics

Scroll of Honour from Institution Of Engineers (I) Calcutta in 1997 as Eminent Engineer

Fellowship of Indian National Academy of Engineering in 1998

CEA Silver Jubilee Celebrations Award for Excellence in Design and Engineering of Power Sector in 2000

Life Time Achievement Award by IEEEMA in 2008 for my contribution on Switchgear and Control Industry in India. PAC World: Which of your awards you consider the most important and why?MP: All of the awards are important to me but the follow-ing three awards are most precious to me: CBIP Golden Jubilee Award in 1983; Silver Jubilee Celebrations Award

the

guru

64

PAC.SPRING.2008

Shri

Mat

a Pr

asad

of CEA in 2000; and the Life Time Achievement Award in 2008 from IEEMA. PAC World: How did you feel when you received these awards? MP: Oh! How do I express it? Very enjoyable, intoxicating and encouraging!PAC World: What do you consider your greatest achievement?MP: Optimizing the design of EHV Network and appreciation of impact of Reactive Power Compensation in Indian Power Network affecting the Security, Reliability and Efficiency of the network.PAC World: And what do you consider your greatest personal achievement?MP: Motivating and providing training to young engineers to enrich themselves with the latest technology and bring the country to a level even with any developed country. PAC World: When and how did you get involved in CIGRE activities?MP: My association with CIGRE started when I was with CEGB Bristol. Dr. John Rushton and Mr. L Annanin of Plant Design Department of CEGB had virtually indoctrinated me with CIGRE philosophy.PAC World: How did you share your knowledge and experience? Did you write papers or books, or did you teach directly to your younger colleagues? MP: I believe that technical knowledge acquired must be distributed to younger engineers in order to motivate and inspire them to rise further in their profession through the

use of acquired technology. There is an old saying that every word is a Mantra, every plant and herb is a medicine and no man can be deemed as unfit. What is scarce is the teacher, with spirit and desire to teach and pass along knowledge.I have not written any books on my preferred subjects but have contributed more than 115 technical papers to various national and international conferences in various countries: North and South Americas, Europe, Australia, China, etc. I have had extensive discussions with the de-legates from utilities and private sector industries and I am satisfied that my papers have created interest.PAC World: Do you still participate in conferences? Do you still present papers?MP: Yes, I do, but my contributions have reduced and that is quite natural. I am also promoting and supporting the need for experienced young engineers to come forward and take part in international and national conferences.PAC World: What do you think about the difference in the technology that we use for protection today and when you started?MP: There is a marked difference due to the onset of solid-state electronics and now the digital techniques. However, the philosophy remains the same. The fantastic journey from four-pole induction cup relays with polarization from healthy or faulty phases to the use of replica impedance using phase or amplitude comparators has been quite rewarding to study and apply.The complex multi-level digital electronics have made the protection relaying much more versatile with multiple be-nefits. The era of Computer relaying has now arrived; Pha-sor and wide-area measurements with GPS appear to be

I hope the full

IEC 61850 will

be applicable and

the design and

testing engineers

will be trained to

handle all such

applications.

65

PAC.SPRING.2008

quite complex and dynamic. The relays seem to transform into a universal type of protection and measurements fully fitting into SCADA and remote integration. “One Substa-tion and One Computer” as a part of a complete SCADA and Substation Automation appears to be the real target.PAC World: What is the difference in the workplace between when you started work and today?MP: The difference is too great to describe. For some time now we have wondered how the whole protection appli-cation, testing and coordination were done in olden days completely on a manual basis; the application gave us very good insight. We are now required to handle the black-box with computer assisted testing. However, the present day technique is versatile and efficient.PAC World: What do you think of the impact of IEC 61850 on the future of protection?MP: How much did we struggle to coordinate the systems provided by different manufacturers for SCADA Load dispatch and integrating various control functions of various equipment? Now with one common platform the coordination becomes very smooth and rewarding. I hope within a couple of years the full IEC 61850 would be applicable and the design and testing engineers would be trained to handle all such applications.

PAC World: What is your definition of retirement?MP: For me the word retirement does not exist. You may be working in one arena and stage and after exiting your role, you go to other areas. The superannuation at the age of 60 is just a milestone to be celebrated to take off to next stage of working with renewed spirit with new tires on the wheel. I cannot forget the spirit of Dr. Charles Concordia whom I had met several times during CIGRE Conferences in Paris where he used to come every two years. He had grown weak with a frail body but he still had a strong will to learn and teach. Now he is no more - at the ripe age of 93.PAC World: What do you think about the Internet?MP: Internet has revolutionized the entire world and equally well the Power System in all the fields. You can realize your dreams through integration of computer, power electronics and Internet. The Internet has become very addictive.PAC World: What books do you like to read?MP: I have an insatiable hunger for purchasing books of all kinds including English and Hindi covering Fiction, History and Region besides technical Handbooks and Classics and above all International Conference Publications. I am a very fast reader. I study different books and like to share with my colleagues in CEA, PGCIL and NTPC who show interests and believe in imparting and exchange of such knowledge.PAC World: What do you like to eat?MP: I am strictly vegetarian, as I believe our human body is designed for only such foods. I like spicy foods and mostly drink tea – for example Darjeeling tea mixed with some Tulsi leaves that I add to it.PAC World: What music do you usually listen to?MP: I like to listen to instrumental classics from known maestros especially those who play sitar, flute shehnai and percussion instruments. My interest in light music, Gazals and good songs from films is always kept alive. When I was younger I was very fond of films - both English and Hindi - and I was a regular visitor to cinema halls. Of late, this has reduced and I prefer watching the good ones on my TV through a DVD player. I have my own collection of film and music CD'sAC World: How do you spend your time when you are not working?MP: When I am not working, I remain at home. I like to read and think about all the questions that we have not answered – where do we come from, are there any other civilizations out there and many others. If we look at Stephen Hawkins and what he has achieved despite his disability – we need to think more about what we all can do with our abilities. I also visit friends for a chat. I wish to provide more time to my family as I had deprived them of the same when I was working full steam.PAC World: What do you think are the biggest chal-lenges for our industry?MP: Technical innovation and new developments are tak-ing place at a very fast pace and one must plan to with-

We need to think

more about what

we can do with

our abilities

Shri

Mat

a Pr

asad

the

guru

66

PAC.SPRING.2008

MP: The whole universe is based on electrons and neurons. Power system engineering is one discipline that throws the real challenge. It is a different path and power system engineers become rather introvert, just as they have to think and act. However, the challenges that come up in delivering the objectives of the system engineering and protection is really intoxicating and once you have fallen in love, you will remain faithful forever. I always give an ex-ample of doctors and lawyers who have to study on a daily basis, consult the latest developments in their profession and then they achieve their goal of eminence. This is true for power system engineers, as they will always have to keep themselves fully aware of the developments through regular study and interaction.PAC World: How do you think we can attract younger engineers to our field?MP: By providing a better working atmosphere with all the necessary tools, better training and prompting them to participate in interactive conferences for exposure to the latest technology.

Good technical documentation with immediate access for references, when required.

Recognition of their talent, experience and occasional pat on their back.

Better payment as specialists, corresponding to their expertise and contribution.

stand the impact of such a fast pace through deployment, structured training and modernizing the course contents in degree and post degree classes to create more avenues in Power System Engineering education. The way the young engineers of any discipline are being pushed blindly towards IT must be handled discreetly. Complete fusion of power electronics, information tech-nology and computer application with special reference to Power System Engineering must be examined by the technical institutes.PAC World: What do you think about the interest of young engineers in power systems protection?MP: Young engineers are like plastic clay and one can mold them into any shape. They are swayed by the winds of explosive development in electronics and feel that this is their final goal. This misty notion has to be intelligently clarified. These days young engineers feel that protection relaying is too complicated, forgetting however that in their own application and relaying, the algorithms are com-mon and very easy to understand.PAC World: You were married in 1954. What is the secret of being together for so many years?MP: IIt is very simple. My wife loves me and believes in me and I do the same.PAC World: If you were standing in front of an audience of young engineers, what would you tell them?

The secret of being together is very simple - my

wife loves me and believes in me and I do the

same.

GALLERY

PAC.SPRING.2008

continued on page 8

Digital Art by Harmeet Kang

Harmeet KangUK

A slightly colorful look

at signal processing

inside a relay

A Very Close Look

Harmeet is a

protection design engineer

at AREVA T&D

Automation, Stafford, UK

who believes that

protection is not just

science, but

art as well

PAC.SPRING.2008

PAC

his

tory

70

Distance protection became the

most important protection techno­

logy in the twentieth century.

History is the tutor of life

Distance Relay R1 Z23bg

by Walter Schossig

71

PAC.SPRING.2008

device. Only after this, a manual raise was necessary ­ an issue that was welcomed by operating staff at this time because it requires a systematic check of the relays. The Ohmmeter functioned as the directional element as well, eliminating the need for special reverse­power relays. A flag showed an operation of the relay and a slave pointer the distance of the fault. For resetting, a winding up of the clock up to a stop position was necessary­ pointer and clock came back into normal position.

Impedance protection of Siemens was put into operation with the 50­kV­ring Bleicherode­Huepstedt­Muehlhausen­Langensalza (Germany) in 1929 . (Figure 6). In the same year distance protection was used for the first time in the 28­kV­grid of Vienna (Austria). To prevent out­of­step of generators and motors, a change from continuous to multi­step time characteristics was observed in the next 10 years. A fast tripping time of less than 0,3 s was achieved with balance beam electromechanical elements. Therefore, these relays had their own name ­ "fast distance protection".

At the same time "express impedance relays" for use in medium voltage grids were developed. Their advantage was

From continuous to multi-zone characteristics First publications and first relays for distance protection

were covered in the last issue. The requirement of the utilities was a decrease of the tripping time to a value less than 2 s. To achieve this they skipped the distance­to­fault depending continuous tripping characteristic and changed to cascaded (multi­step) or mixed characteristics. The distance relays provided by BBC and Siemens in 1928 still used the continuous characteristic. Stoecklin J. proposed and BBC developed a Relay that used the crossed­coil­ohmmeter (known from measuring devices). It was patented for selective protection. The base time of this relay was 0.5 to 1 second, which increases with the distance to the fault up to five second. The device consisted of three mechanically united main parts. The impedance startup started a timing mechanism, while an ohmmeter limited the relay’s time. The timing element ­clockwork with manual winding ­ measured the time and operated exactly. It disburdens the current system; the result was a well working device with small power consumption, even with low currents. The clockwork stored approximately 100 seconds operating time ­ equal to 50 operations of the

BiographyWalter Schossig

(VDE) was born

in Arnsdorf (now

Czech Republic) in

1941. He studied

electrical engi-

neering in Zittau

(Germany), and

joined a utility in

the former Eastern

Germany. After the

German reunion

the utility was

renamed as TEAG,

now E.ON Thuerin-

ger Energie AG in

Erfurt. There he re-

ceived his Masters

degree and wor-

ked as a protection

engineer until his

retirement. He was

a member of many

study groups and

associations. He is

an active member

of the working

group “Medium

Voltage Relaying”

at the German

VDE. He is the

author of several

papers, guidelines

and the book

“Netzschutztech-

nik (Power System

Protection)”He

works on a

chronicle about

the history of

electricity supply,

with emphasis on

protection and

control.

HistoryProtection

This article discussees the next phase in distance protection development

From Protection Relays to Multifunctional

Distance Protection

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PAC.SPRING.2008

the use of a step time characteristics (Figure 3). They were able to protect 70% of the length of line with an operating time of 0,3 s . Neugebauer,H. and Geise,Fr., Siemens, proposed an express impedance relay in 1932. It was the first distance relay in an economical single plate housing per end of line. Fast distance relays were used to achieve short tripping times in the EHV­grid (solid earthed star point). Usually they had three measuring elements (in the English­speaking countries up to six). Single­pole autorecloser with definite 3­phase trip was possible now.

In the medium voltage, the grids had an isolated star point. Petersen,W. invented the earth­fault neutralization in 1917. Since then, especially in the German­speaking countries, compensated grids are quite common. The capacitive earth fault current is compensated by the inductive current and continuing operation of the grid is possible. Fast distance relays with only one measuring element were sufficient to detect 2­ and 3­phase short circuit faults.

The distance protection in Europe was the most often used protection technology on mashed or parallel­operated high voltage grids. When the short­circuit power in the grid became higher, the requirement for fast tripping on the whole line length became important. Ackermann already showed a proposal for a step protection in 1920/21. This was used in Siemens reactance relays in 1930, in the Oerlikon­Mini­mum­Impedance­Protection and the newer distance relays of Westinghouse Co. and General Electric Co.

AEG developed their first fast distance relay in 1934 (SD1). It uses pure three­step characteristics; fast tripping times of 0.3 up to 0.4 s were achieved. As an under­impedance protection it uses two balanced beams, which were set up to different lengths of the line. Additionally it consists of a 3­step timing element and an iron­cored dynamometer as a directional element. Startup was realized with built­in overcurrent elements or ­ in a separate housing ­ with under­impedance elements. The right housing consists of measuring elements and the directional element with a tapped voltage­matching transformer (for impedance setup). The other two devices contained the startup, the choice of measuring values and

the three­step timing relay. For the detection of two­phase to earth fault the SD1 used for the first time the sum current and a change to the phase­earth voltage for the measurement of the impedance. The one­system protection relay required the right choice of measured values. Special auxiliary relays, with strong contacts were necessary. The SD1 was already equipped with HF­channel to realize a directional comparison protection. For the medium voltage, the less complex SD2 was provided.

The Arrival of Rectifier TechnologyIn 1937 AEG presented as a first big vendor the use of

metal rectifiers in a distance relay with their SD4. Since then, it was possible to reduce the measurement of the short­circuit loop to a DC­measurement. Influenced by voltage and current, a rectifier operates sensitive plunger coil relays. The power consumption in the voltage circuit could be decreased ten times ­ in the medium voltage it was possible now to supply several distance relays with one busbar­voltage­transformer.

After the good experiences with rectifier technology in Germany, a bridge connected rectifier was common at the end of World War II. Two or three sets of rectifiers supply relays with one moving coil (Figure 7). Voltages and currents were provided with interposing transformers to the Graetz­Circuit. A polarized moving coil relay was in the shunt arm of the anti­parallel switched rectifiers. It closed the contacts at a certain ratio of voltage and current.

Due to the very low power consumption of the rectifier measuring systems it was not necessary to rectify the whole transformer current ­ only a current proportional voltage over a diverter resistor was necessary. In the first AEG SD4 relays (1934) this resistor was connected via a phase selection contact to the affected current circuit.

The selection transfer, developed in the last two years of World War II the resistance was realized as a 3­pole one. in relays with doubled earth fault detection as 4­pole. The secondary circuits of the current transformer in that case did not need to be switched. The selection of current was realized with normal contacts. In that case in the current as in the voltage a correct selection of the measuring values was realized.

1 Distance relayRAZOG, ASEA, 1970

3 Distance protection characteristic with express contact & maximum operating time

Distance characteristic

t [S

]

2 Distance relayLG1, BBC

Z [Ω]

73

PAC.SPRING.2008

When the corresponding phase selection contacts of voltage and current were from the same auxiliary relays it was simple to justify the contacts to open and close at the same time or to open the current circuit a short time before the voltage circuit and close one a short time after another.

A new measuring principle based on comparison of the peak values with rectified values, was introduced with the distance relays SD4. A bridged­connector rectifier allowed a comparison of any combination of voltages and currents for the estimation of a difference and the estimation of impedance and power (direction). Mixed impedance characteristics (blocking of the circle characteristic along the R­axis) were available to eliminate the resistance of electric arc from the estimation of the distance.

The Impact of Arc Resistance and Power SwingThe impact of the electric arc resistance on the distance

measurement was a main issue for a long time. Very early the utilities performed extensive and systematic short circuit tests (e.g. Bayernwerk AG in their 110­kV­transmission­line­grid (1926/27) and Preussenelektra (1929) ­ both in cooperation with the vendors ­ AEG, BBC and Siemens. Under impedance­startup in off­peak periods was tested for suitability during these tests and new requirements for further improvements were found. At first, they tried to eliminate arc resistance with real reactance relays. BBC and Siemens provided the first solutions in 1928. Maloperation of relays was observed when power swing occurred between power plants (seen as short circuits by the relays). This was frustrating for the engineers. Power swing blocking and power swing relays were developed. Gutmann,H., AEG patented the

modified impedance measurement in 1944. The measuring value of the modified impedance element was:

IIkUZ ⋅+

=ˆ

An arcing reserve of 60% was possible with consideration of line angle at the relay’s trigger point.

100 % of Line Length with no time delayStarting in the 50's of the last century, fast distance relays

in connection with automatic reclosers were widely used for the detection of lightning strike faults over the whole length of the line with no time delay ­ the "overreach".

An auxiliary device was used to enlarge the zone of the first stage up to 115% of the length of the protected line . After the first trip, the value was decreased to the common 85…90% ­ after an unsuccessful reclosing there was guaranteed selectivity for the second trip. Use of a power line carrier (PLC) channel for accelerating the trips on both sides of the line allowed instantaneous protection of the whole length of the line with the 15%­overreach. This approach was used where PCL connections were available (remote control, phone, remote measurement etc.). The first installation was realized in Germany in the 220 kV grid of Preussenelektra in 1955.

At the end of the 60's distance protection was extended with "distance dependent directional comparison protection

4 Distance relay RD7, 1958

The impact of the electric arc resistance on the distance measurement was a main issue for a long time.

5 Fast distance relay SD36, AEG 1986

6 Observing the Siemens impedance pro-tection when energizing a 50 kV line

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PAC.SPRING.2008

N-Relays with balanced-beam element 30 years before). Now a higher sensitivity was reached ­ 1 % of nominal voltage at nominal current. A special series element allowed an angle of up to 30° (inductive) required when used in medium voltage cable systems. Increasing the pressure of contacts for high­sensitive distance relays allowed a further improvement of reliability. A big advantage was the direct­CT­powered operation ­ it was useable in stations without batteries. The switch to the next stage was realized with " synchronous time relays" (with synchronous motor).

In the USA in almost all cases three balanced­beam­relays were used ­ permanently connected with voltage and current. They were set up according to three stages with different time settings. Thus, a stepped characteristics was available. German Railways used a similar system.

„Self-Supervision"Some of the first distance relays were equipped with voltage

transformer supervision. The N­relays (PAC World, Winter 08 issue, Figure 4) had a built­in voltmeter. Another possibility was the use of external or internal glow­lamps. Aigner developed a rotating ­field discriminator for supervision of interruptions of one or two phases and of the existence of a right rotating field. A fault in the current circuit could be only detected with the startup of sensitive zero­sequence relays. The loss of auxiliary voltage could be visualized with a flag relay. Development of microprocessor­based relays allowed a further self­supervision (measuring values, CPU-failures, trip-curcuit, circuit breaker supervision…).

Guidelines for Distance Protection - Further Steps Lessons learned in the time before World War II show,

that a joined operation of adjasent protection systems was

systems". In these devices the directional information and the measured distance are evaluated. The comparison of distances is performed in the first stage of distance protection only. Several methods are used for tripping. In the United States it was quite common to use "blocking" ­ the tripping command of the own protection is blocked by the PLC­signal of the other station. Another possibility is "permissive intertripping". If a fault occurs and the device should trip, a permissive signal is provided to the other end. Last, but not least, "inter­tripping " should be mentioned. In that case the distance protection trips its own circuit breaker without a signal from the opposite station. This is also communicated to the other end –it "inter­trips". This scheme realizes a backup protection ­ at the opposite site neither a distance estimation nor an estimation of direction is necessary.

In the relay SD14, developed by AEG in 1954, the directional element was realized with a small moving coil relay instead of a plunger coil system. The mode of operation is comparison of absolute values of V + I and V – I (as in the

8 Transmission line protection distance relay LZ91 (BBC)

7Circuit for measurememt of the impedance

Withdrawable

boards allow

quick fix of

problems in

solid state

distance

relays.

Self-supervision plays an important role in

improving the performance of distance relays.

10 Distance relay DD2, EAW

I U

Current circuit Voltage circuit

9 Distance relay 7SA500, Siemens, 1986

75

PAC.SPRING.2008

not successful in any case and that the vendors did not allow that. The same problem occurred when different vendors were used in the same grid. That is why the utilities defined their requirements to allow the usage of relays of different vendors in one grid. The pre­condition to do that was to harmonize the operation behavior of relays. The German VDEW proposed an "Agreement of Utilities for Harmonization of Distance Protection" in 1951. The paper describes relays of the following vendors ­ AEG ­ SD4, BBC (L3, LG1­ and LG2­Relays, Figure 2) and Siemens RZ24­/ RK4­Relays.

The BBC relays were reactance protection, while AEG and Siemens provided impedance relays (elimination of arc resistance with a mixed­impedance add­on). The guideline defines startup (2­and 3­pole, range of overcurrent or under ­impedance­startup); voltage; dead zone; first­zone­time; smallest measuring impedance; maximum operating time, detection of doubled earth faults; power consumption.

Other recommendations were regarding the mounting and the usage of the DC measurement (shunt instead of interposing transformers). The recommendation for timing elements was motor drive instead of clockworks (higher moment of force and improved resistance against contamination). Ulbricht,R. und Kadner,G. publish a bulky guideline for time grading coordination with distance protection in the GDR (Eastern Germany) in 1958. The document considers the special circumstances in the GDR after World War II ­ 13 different types of relays with different characteristics were available. Therefore, the document describes selective time interval and impedance, single and parallel lines, impact of measuring failures at transformers, arc resistance, detection of doubled earth faults; maximum operating time and calculation of short­circuit currents.

ASEA (Sweden) produces the distance RYZKC relays since 1950. To decrease tripping time distance protection was used as busbar protection in transformer infeeds. EAW (GDR) introduced RD7 in 1952. Pushing the button (Figure 4) performed a functional test of the relays (only if the tripping circuit was interrupted). Austrian Rail (ÖBB) used an auxiliary distance relay in their 16 2/3 Hz grid since 1957. It was developed by Gutmann,H, AEG, and was named SD4/WZD0. It was a joint initiative with German Rail and AEG and could be used for non­fading earth­faults as well (the other phase was earthed in another station, and then a doubled earth fault occurs and the faulty line could be tripped).

Backup ProtectionLively discussions regarding the use of backup protection

started in 1960. Norway, Russia and England preferred doubling protection in the EHV grid. They used two similar or equal relays. An expert from the United States reported the „ breaker­and­a­half approach" ­ the reserve was the circuit breaker, because failures of breakers and tripping circuits are more likely than with relays and measuring transformers. The EHV grid in Germany uses a backup relay per feeder ("main" and "backup" or "system 1" and "system 2"). Both systems are separated; up to today, it is quite common to merge different type relays (e.g. distance and differential protection) of

11 Distance relay RAZOG, ASEA, 1970

12 Distance relay PD531, AEG, 1991

This is one

of the examples

for the usage of

microprocessors

in distance

relays

13 Distance relay 316LZ (ABB,1990)

The first

distance relay

with polygonal

characteristic

was produced

by ASEA

in 1970

Resistive reach setting Reactive reach line

Rb

zone 1

X1

R

Rb

Rb

zone 2

zone 3

Terminal rack of type THR from 1975

The 1999 OHMEGA version

PAC

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PAC.SPRING.2008

different vendors. To avoid malfunction a "2 out of 3 circuit" was discussed often but did not became established.

Introduction of ElectronicsThe first electronic distance protection was used in 1959.

The French EdF reported the commissioning of a transistor based distance protection in the 200 kV grid. In its first year it worked properly in 38 cases (of 40 faults). According to vendor’s publications the relay needed only 2 VA (in current and voltage) and the stepped characteristic should be nearly perfect, not depending on the short­circuit current. Other documents describe an English distance relay with Mho­circle, based on transistors. It was developed for the South African EHV grid and was proved of value. It should be mentioned that the vendor at this time warned against big enthusiasm for “transistor relays”.

The sophisticated electromechanical relays in bridge­connected rectifier circuit were better and more economic at this time. The first distance relay with polygonal characteristic (Figure 11) was produced by ASEA in 1970 ­ the three­phase static relay RAZOG (Figure 1) with a shortest operating time of 21 ms.

Mann and Morrison, UNSW (Australia) developed algorithms for the calculation of line impedances in the same year. Rockefeller,G.D., Westinghouse; published an IEEE paper one year before and patented a digital distance protection

in 1972. Before that he did together with Gilchrist,G.D., (PG&E) a field test with digital line protection PRODAR and a computer in a 230 kV substation in 1971.

It is worth to mention the EHV directional comparison protection RALDA (ASEA) from 1976. It is based on superimposed components principle and achieved a time for estimation of a fault of 2.4 ms. Cubicles for each feeder with swing frame and plugs, introduced at this time, allowed an easy change and combination of withdrawable boards (Figure 9). Beginning in 1985, distance protection with digital measurement was used in the medium voltage as well ­ AEG introduced the fast distance relay SD36 (Figure 5).

Examples for the usage of microprocessors in distance relays are: 7SA500 (Siemens, 1986 ­ Fig.9); 316LZ, (ABB, 1990 ­ Fig 13); PD531, (AEG, 1991 ­ Fig.12); DD2, (EAW, 1996 ­ Fig. 10) and OHMEGA, (Reyrolle, 1999 ­ Fig. 14).

These solutions were the quantum leap ­ from impedance depending short circuit protection to multifunctional feeder­relays. The development of the different generations of numerical protection and their advantages will be covered in a special article later.

Despite of comprehensive tests, type tests according to international standards by the vendors, certifications and commissioning tests with sophisticated test sets, staged short circuit faults are still valuable. In these tests vendors, utilities and universities contribute. A good example was the international line 750 kV Zapadno­Ukrainskaja (Western Ukraine)­ Albertirscha (Hungary) with the distance relays PD551 (AEG) and 7SA502/511 (Siemens) Figure 15.

A special challenge for protection engineers was the commissioning of a six­phase transmission line 93­kV­ Goudey Station ­ Oakdale, NYSEG (US) in 1992. Sambasivan, S and Apostolov,A.P. solved the protection problem with digital differential relays LFCB, directional comparison relays LFDC, distance relays LFZP and a high­speed programmable logic device LFAA (all from GEC ALSTHOM) (Figure 16).

Any comments or questions please send to: walter.schossig@pacw.org

www.walter­schossig.de

16 Protection of a six-phase line or distance relays OPTIMHO LFZP, GEC ALSTHOM

15 Test distance relays PD551, AEG and 7SA5, Siemens in a 750 kV grid

14 Distance relays THR and OHMEGA

10 kV

GOUDEY

103.7 km 21 km

330 kV

373.3 km (78.3%)

750 kVOAKDALE

Six-phase line protection, one end, three-phase group A-C-E or B-D-F

A - C - E

B - D - F

67G

78

21

87 62

21G

21

LFCB

LFDC

MCTI

LFZP

477km

750 kVUkraine Hungary

77

Marco C. Janssen

PAC.SPRING.2008

I thi

nk

Does our sudden interest for “Smart Grids” mean that up to now everything we did was stu­pid? I don’t think so.

When I look back at my first years as an engineer in the power indus­try I have to say that I had some extremely smart colleagues who tried to teach me everything there was to know about power systems and their behavior. And I can say I had to learn a lot!

Until recently smart engineers handled the most complex issues without grids being as “smart” as we believe everything should be today. Given the fact that electri city has become a reliable commodity in our society and that we all hea­vily rely on it, must mean that they have done something right.

Why is it then that we believe that, to solve the issues of our ages, we have to throw technology at e verything? I was brought up with the philosophy that simple was better.

So why are we making things more complex then? In some ca­ses we make them so complicated

Do we really need Smart Grids?

The buzz word of our time is “Smart Grids”. It seems that suddenly everything has to become “Smart”. When I look at this it makes me start to think…

way. On the other hand however I get the feeling that we are making things unnecessarily complex by throwing technology at any pro­blem we try to solve. So what is the true answer?

As so often I believe the truth lies in the middle. Yes, we can improve the utility business by combining information and using the newest technologies. On the other hand I also believe that it is wise to think before we act. We should remem­ber that automation for the sake of automating has never led to cost effective solutions. So pursu­ing “Smart Grids” for the sake of having “Smart Grids” will in my opinion not lead to long­lasting, feasible solutions.

So what should we do? We should never forget to ask at least one important question. “Why are we doing this?” When we start answering this question we will most likely find the right answers to what we really need to do and when.

So I look forward to seeing many new “Smart Solutions” that are be­ing built for all the right reasons.

that even the smartest of engineers have trouble following what is going on. Are we trying to com­pensate for the fact that we are no longer smart enough ourselves or is there some other, deeper, reason why we are doing this?

When I try answering these ques­tions myself I struggle to come up with answers. On the one hand I strongly believe that a combina­tion of all the available information existing today within so­called is­lands of automation, can lead to better and even simpler solutions. Which allow utilities to deal with today’s challenges when operating a power system in a more efficient

BiographyMarco C. Janssen

graduated the

Polytechnic in

Arnhem, The

Netherlands and

further developed

his professional

skills through

programs and

training courses.

He is President and

Chief Commercial

Officer of

UTInnovation LLC

– a company that

provides consulting

and training

services in the

areas of protection,

control, substation

automation and

data acquisition,

and support on the

new international

standard IEC 61850,

advanced metering

and power quality.

He is a member of

WG 10, 17, 18, and

19 of IEC TC57, the

IEEE-PES and the

UCA International

Users Group.

PAC.SPRING.2008

79

B5 is one of 16 Study committees of CIGRE. Its scope is to facilitate and promote the pro­gress of protection and automation.

industryreports

The business environment for utilities has changed drastically due to the restructuring of the world electrical energy markets. The profitability pressure has demanded reconsideration of the complete secondary system approaches, to identify and beneficially utilise all possible synergies between the tasks of protection, control and monitoring. All assets have to be used in more profitable ways, whilst the security of on-demand energy supply is increasingly important, due to the increasing costs for energy not supplied and the severe impacts that blackouts now have on communities, industry, commerce and nations.SC B5 covers all the secondary equipment and systems installed within substations. This includes power system protection, substation local and remote control, automation, metering, monitoring and recording.

PrioritiesAutomation of substations, with integrated protection and control systems and the use

of the new IEC 61850 Standard are major industry trends. The application of IEC 61850 will be extended to further areas and its impact will demand continued review and study to detect any general problems, so that they can be addressed before they become too widespread. CIGRE SC B5 provides a unique channel of feedback to IEC in this respect.

CIGRE SC B5 Protection and Automation

1 Evolution of number of devices for a protection and control system

Communications within substations are

covered by the new and expanding

IEC 61850 standard.

1960 1970 1980 1990 2000 2010?

4 Cubicles,"Soft" Devices

11 12 6 6 3

4 4 4 4 2

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icle

s, >

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ices

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ices

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by Ivan De Mesmaeker, ABB, Switzerland

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RE

B5

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Relevant issues related to the IEC 61850 standard are:

Functional testing of IEC 61850 based systems

Applicat ion of protect ion schemes based on IEC 61850

Engineering Guidelines for IEC 61850 based systems

Maintenance strategies for Substation Automation Systems

Impact of security requirements on SAS

The introduction of digital hardware and numerical protection technology has greatly transformed the planning, operation and maintenance practices for protection systems. Design engineers now require appropriately adapted guidelines to support their work. Several working groups are preparing reports about on-going trends and offering recommendations for the protection of generators, transformers, shunt reactors, overhead lines or cables and busbars.

Modern numerical relays are highly integrated and contain a great number of protection and additional functions. Special attention is

given to the increasing trend for functional integration. “Bay Units” for combined protection and control are now accepted at distribution levels and this trend may migrate to the transmission levels. Numerical relays are widely self-monitored. Regular routine testing will therefore be increasingly replaced by condition-based maintenance, depending on how comprehensive the self-monitoring is.

System-wide monitoring and protection

Wide area disturbances due to loss of stability or voltage collapse, still occur and may become more probable in the future, with higher system loading and by regularly operating plant and power systems towards their design limits and capabilities. On the other hand, wide-band communication links, adaptive digital protection and GPS synchronized data acquisition provide platforms for novel system wide monitoring and protection techniques. In many countries a large part of the business is the retrofitting of existing plants and

systems because of life-expiry, or because of recommendations about the need to change current practices. The development of life-cycle maintenance and risk management strategies are therefore expected.

Software tools for dynamic simulation, management of relay settings, disturbance or fault record analysis, or how to write specifications are improving.

Emphasis on education is a challenge, considering that protection is generally not a topic dealt with to any significant depth by colleges and universities, and that engineers entering in the power engineering sector in general are becoming rare.

Numerical technology combined with advances in information management contributes to the more efficient management of power networks, but it introduces problems and issues in four main areas: level of integration, standardisation, information management, wide area monitoring and protection.

The integration of ever more functions into fewer devices and systems has been an increasing trend – especially over the last 10 years or so. Figure 1 indicates the evolution of the number of devices for a protection and control system covering a station with six 220 kV lines and eight 16 kV feeders.

Protection function integration is now the norm and combined with high level of self-supervision in numerical protection devices actually supports a higher degree of integration - a trend that will continue in the future.

PAC.SPRING.2008

reviewing the guide before it was published in 2005. The result is IEEE STD C37.119 Guide for Breaker Failure Protection of Power Circuit Breakers – 2005. The following are excerpts from the guide Remote versus Local Backup.

If remote backup is employed, then the time delayed overreaching element (Z2) of the relay at a remote substation operates for a fault on line BC when local breaker fails to clear the fault on a line. Operation of remote breaker interrupts the load connected downstream of it. If local backup is used, when a breaker fails, local breakers clear the fault. The load is not interrupted in this case on the line with the remote substation. Local backup provides faster clearing and less loss of load than remote backup:

In the basic scheme for breaker failure protection, as soon as the relay issues a trip to its breaker, a breaker failure timer is started. If the fault still persists after the timer times out, then a breaker failure condition is declared, and the breakers connected to the bus are tripped.

Breaker Failure Initiate (BFI) is the signal coming from the primary

How do u tilities handle backup protection? What are the advantages of using local backup over remote backup? How is breaker failure protection being implemented by utilities? What are the pitfalls in using the breaker auxiliary contact for breaker position? Where do you go to get these answers? Prior to 2005 no guide existed in applying breaker failure protection to answer any of these questions. The only previous article written by the PSRC was in 1982. An IEEE Power System Relaying Committee Working Group w rote a report t itled “Summary Update of Practices on Breaker Failure Protection” and published it in the IEEE Transactions on Power Apparatus and Systems. Vol. PAS 101, no.3, pp 555-563. March 1982.

To answer these questions and provide a reference for engineers to for future generations, the IEEE PES PSRC Substation Subcommittee formed a working group to write a guide on this subject. This working group was formed in 2000. 62 industry experts from utilities, manufacturers, academia and government agencies put in many hours of effort in writing and

The Power System

Relaying Comettee is in

the Power Engineering

Society of IEEE.by Roger Hedding, ABB, USA

T h e m o d e r n p r o t e c t i o n technology facilitates new solutions and functions to tackle several fault management problems, such as the protection of combined cable-overhead lines (adaptive auto reclosing with ability to distinguish potentially transient overhead line arcing faults from solid cable faults) or the protection of parallel and/or multi-terminal lines.

StandardizationStandardization covers two main

aspects: Typical Bay and Station levels and Communication.

Independently of the applied technology, it is possible to define the required functionality and performance of each protection and control function (tripping times, precision, etc) for each type of Bay, in each type of substation. Users can define additional requirements, such as the permitted level of functional integration, the physical scheme architecture, the requirements concerning DC auxiliary/tripping supplies, test facilities, wiring and inclusion of some specific devices. Functional requirements can also be listed at the Station level, covering HMI (Human Machine Interface), event and alarm lists, etc.

Specifications need only be functionality based, with reference to a single line diagram, rather than detailing specific protection system devices.

CommunicationsCommunications in substations

should assure interoperability between compliant Intelligent Electronic Devices and functions within the substation. They should be future-proofed, i.e. able to cope with the fast developments in communication technology compared to the more slowly evolving application domain of power systems.

These are very ambitious goals, which demand that all secondary substation devices and functions must be examined with regard to their communication performance and requirements.

Guide for Breaker Failure Protection Published

IEEE C37.119 Guide for Breaker Failure

Protection

TimerAND50BF

BFI

62-1

Breaker Failure

Scheme Output

ABC Breaker Failure

Scheme Output

2 of 3

Timer

AND

AND

AND

TimerOR

BFI

62-1

OR

62-2

50BF

50BF

52a TimerANDBFI

BFI

62-1

Breaker Failure

Scheme OutputOR

OR

AND

Timer

50BF

100msec

Low gas pressure contact

BFI Standard BreakerFailure Scheme

Breaker FailureScheme Output

Breaker Interrupt Time

50BF current detector

Protective Relay Time

Margin TimeFault Cleared

Fault Occurs

Local Backup Breaker Interrupt Time

Remote Breaker Interrupt Time

Transfer Trip Time

RelayTime

62-1 BF Timer TimeBFI

Aux Trip

by Roger Hedding, ABB, USAIE

EE

PE

S P

SRC

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PAC.SPRING.2008

protection to trip the breaker. An overcurrent fault detector (50BF) is employed to determine if the fault is still present. 50BF will drop out if the breaker clears the fault. The guide discusses issues related to the setting and drop out of the fault detector (50BF). The timing for the scheme is seen below. (Fig. 1)

In EHV transmission systems, the total fault clearing time needs to be less then the power system critical clearing time plus some margin. The power system critical clearing time is a function of the steady state stability limit for the power system. Since the critical clearing time to maintain system stability is greater for single line to ground faults than three phase faults, some schemes employ dual timers. (Fig. 3) The 62-2 timer can be much longer than 62-1.

For lower voltage systems, the total clearing time is chosen to limit damage to equipment. Some faults such as transformer or reactor faults have such small currents that a fault detector can not be used. In those cases, a breaker 52b contact is used for indication of breaker operation. (Fig. 4) In some cases where there is a known problem with a breaker before it’s called to trip, a bypass scheme can be employed. (Fig. 5)

In this scheme, if there is low gas pressure and the primary relay calls for a trip, the breaker failure scheme is bypassed and the surrounding breakers are tripped immediately. Other schemes are also discussed.

A section of the guide deals with design considerations for the breaker failure scheme. Several factors need to be considered. Among them:

Scheme operation should only occur when expected and desired.

Scheme operation should be independent of the types of failures detected in the breaker. For example, the failure mode of the breaker trip coil should not effect the schemes ability to detect the failed breaker and to properly isolate it from the power system.

Scheme operation during loss of dc power to the failed breaker.

Sufficient overlappin g of protection and isolation switches to allow maintenance and overall testing of the scheme.

Proper application of auxiliary tripping relays.

Selection of properly rated inputs and outputs when the breaker failure is integrated as part of the equipment protection package and when user selectivity in rating is provided.

Proper application of dc circuits and avoidance of mixing supply sources.

Minimizing the impact of dc transients.

Other sections of the Guide deal with factors that influence settings, communications based breaker failure schemes, and end to end testing.The guide is available through the IEEE Standards Department

1 Total fault clearing time 5 BFP bypass scheme

2 Basic Breaker Failure Protection scheme

3 Dual-Timer Breaker Failure Protection scheme

4 Breaker contact use for bre-aker operation detection

83

PAC.SPRING.2008

Protection, Automation

and Control conferences

around the world provide

forums for discussions and

exchanging ideas that help

the participants resolve

the challenges that our

industry faces today.

conferencereports

PAC conferences around the world

Chicago,

Illinois, USA

page 89

IEEE T&DConference 2008

Tampa ,

Florida, USA

page 84

DistribuTECH 2008

Spokane,

Washington, USA

page 88

Western PowerDelivery Automation

College Station,

Texas, USA

page 86

Texas A&M Conference forProtective RelayEngineers Glasgow, UK

page 86

The 9th International Conference-Development in PS Protection

Clemson,

South Carolina,

USA

page 85

2008 Power SystemConference

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Th e 1 8 t h D i s t r i b u T E C H Conference & Exhibition was held from January 22 to January 24, 2008 at the Tampa Convention Center in Tampa, Florida. It is one of the key events in North America that gives the opportunity to many electric power system specialists to learn about the latest trends in technology and exchange ideas about the future of our industry.

The areas covered by the event include automation and control systems, information technology, transmission and distribution

The full day tutorials of interest to the PAC community covered:

Cost-effective distribution reliability improvement

Distribution automation – strategies for success

Substation automation projects: design issues, alternative approaches & cyber security considerations

Substation protection, controls & communications in the new century

Cyber security risk management Using the IEC 61850 standard

for communication networks and systems in substations

The conference started with a keynote session that included presentations by Spencer Abraham, the tenth Secretary of Energy in United States history, Don Cortez - Division Vice President of Regulated Operations Technology for CenterPoint Energy, the nation’s third largest combined electricity and natural gas delivery company and Jeff Sterba - Chairman, President and CEO of PNM Resources.

The conference papers were presented over three days in six tracks, four of which included subjects related to PAC. The substation automation track had sessions covering utilities experiences in substation automation, IEC61850

Industry

leading

manufactur-

ers partici-

pated in the

exhibition

The focus of the conference

was new technologies and

their impact on the future

of the industry.

engineering, power deliver y equipment and water utility technology.

DictribuTECH was attended by more than four thousand specialists from around the world. They visited and discussed the latest technology with approximately three hundred exhibitors, representing more than fifty product groups and more than twenty unique services.

The conference was preceded by the Utility University that included full and half-day tutorials on subjects of great importance to the industry.

The Tampa

Convention Center-

was the conference

venue in Florida

DistribuTECH 2008 held in Tampa, Florida

85

PAC.SPRING.2008

application and experiences, making systems interoperable – the standards evolution continues, designing and deploying successful substation automation and a look at standards-based substation network implementations designed for extensibility, resiliency and security.

The distribution automation track included sessions on pulling together multiple technologies to become the “utility of the future”, innovative integration of protection and automation for feeder restoration, keeping up with communications - the path to EZ automation and extracting information out of the automation data well.

The TransTECH track included a session on wide area monitoring systems and phasor measurements and their impact on the reliable operation of the grid.

PennEnergyJOBS Career Fair at DistribuTECH provided a selection of the top industry employers looking to recruit skilled energy professionals.

Several exhibiting companies sponsored a Ford Mustang Giveaway at the end of the show. Attendees that visited the booths of all participating vendors had to be present at the drawing. The winner claimed his prize within two minutes.

The 2008 Power S ys tems Conference was hosted by Clemson University at the Madren Center, Clemson, South Carolina from 11 March to 14 March 2008. The focus of the seventh annual conference was system issues associated with Advanced Metering, Protection and Control, Communication and Distributed Resources.

The program included a number of tutorials by leading power industry companies. All tutorials were available to all registered attendees at no additional cost and covered the following topics:

Practical Applications Protective Relaying Seminar Renewable Energy Challenges:

Present and Future Directions Substation Automation IEC

61850L eading indust r y expert s

were keynote speakers: Intelligent Grid - The Road Ahead - Bogdan Kasztenny, GE Multilin; Power

Engineering in a War Zone - Jim Hicks, Shaw Engineering Service Group; Future of the Smart Grid - Matt Smith, Duke Energy; PHEV's: Strategic Opportunities for Utilities - James Poch, Plugin Hybrid Coalition of the Carolinas; Innovations in Technology Changing Power Systems Today - Ed Schweitzer, SEL; Future of Nuclear Energy - Stephen Byrne, SCE&G

Four panel sessions gave an opportunity to the interested participants to discuss:

Integrating plug-in hybrid electric vehicles with distribution systems

Integrating advanced metering with distribution systems operation

Synchrophasors: principles, application and implementation

Utility of the future The seven paper sessions included

papers in the following groups: Protection of distribution

systems with distributed generation; Stability of distribution systems ; Renewable energy in power systems; Advances in digital protection; Synchrophasors ; Wide area monitoring & control; IEC 61850 applications.

An exhibit area allowed eight of

the leading industry companies

in the field to demonstrate the

latest solutions that they offer

to the market.

DistribuTECH provides more current resources, new industry technologies, and fast-track networking opportunities. Clemson Power Systems

Conference 2008

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The attendees enjoyed not only

their time together, but also an

art collection of international

significance which includes

works by Rembrandt, Botticelli,

Van Gogh and Lippi.

The Texas A&M 61st Annual Conference for Protective Relay Engineers was held from 31 March to 3 April 2008 at College Station, Texas. The conference was hosted by Texas A&M University. As Prof. B. Don Russell, Chair of the conference said in his Welcome address “…the conference has provided the best available information on protective relay applications and technology. With the changes that have occurred in the electric power industry and with the business emphasis on efficiency and cost savings, the relay conference is even more important than ever.”

Two pre-conference events were offered to the participants:

A presentation on the new “Guide for Protective Relaying Application to Distribution Lines” produced by a working group in the IEEE Power Systems Relaying Committee.

Presentation on Ethics in Engine- ering Practice.

Manufacturers seminars discussing latest advancements in protection technology were also held at the College Station Hilton before the start of the conference.

The papers were presented in several general sessions and tracks:

Power Engineering Track Industrial Track Communications Track Real World Experience

Three Break-Out Sessions discussed Phasor applications, Commissioning and testing of relays and Distance element challenge.

The papers presented during the different sessions triggered interesting discussions. This was to a great extent due to the practical focus of the presentations.

Demonstrations of the latest technology and discussions of their principles and applications help the participants improve their knowledge in the field of protection and control.

Texas A&M Protective RelayConference, USA

The conference

was hosted by

Texas A&M

University

The success of the conference

shows that at this time of

rapidly changing technology,

a period of four or even three

years between the conferences

is too long.

Th e 9 t h I n t e r n a t i o n a l Conference on Developments in Power System Protection was held from 17 - 20 March 2008 in Glasgow, Scotland, UK. This is the largest specialized protection conference in Europe that is held at three or four years intervals at different locations.

The conference venue was the Crowne Plaza Hotel in Glasgow. This is Scotland’s largest city with a population of 600,000. It is the commercial capital of Scotland and one of Europe’s top 20 financial centers. The hotel overlooks the River Clyde and is located next to the Scottish Exhibition and Conference Centre (SECC) and opposite the Glasgow Science Centre.

Developments in Power System Protection 2008

87

PAC.SPRING.2008

Glasgow

is the

largest city in

Scotland

The conference was held in

Glasgow, Scotland, UK

A one day tutorial on IEC 61850 and its application to protection systems was presented by some of the leading industry experts with the idea to improve the attendees understanding of the standard and help them in its successful implementation in different projects.

The conference started with two keynote addresses:

Trends in Protect ion and Substation Automation Systems and Feed-backs from CIGR E activities was delivered by Ivan de Mesmaeker, Chairman of Study Committee B5 of CIGRE. He addressed the main important issues regarding protection and substation automation systems:

the possible level of integration, the standardization aspects and the impact of IEC 61850, the information technology and the overall system protection scheme.

The second keynote speaker was Javier Amantegui, Protection M a n a g e r o f I b e r d r o l a a n d talked about the challenges and opportunities faced by utilities using modern protection and control systems.

The papers selected by the conference organizing committee ranged from research concepts and ideas to technical issues and industrial applications.

The papers belonged to the following main categories:

Relay design and protection

principles Impact of utility changes on

protection Funct ional integrat ion of

protection and controlThe papers were presented in

three forms: Oral presentation sessions Short presentations sessions Poster sessions

A dedicated exhibition ran in parallel to the DPSP 2008 conference, covering a range of products and services.

The Conference Dinner was held at the prestigious Kelvingrove Art Gallery and Museum, one of Scotland 's most popular tourist attractions.

The conference

was held at the

Crowne Plaza

hotel next to the

SECC

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John Tengdin delivered the key-

note address at the opening of

the conference.

substation engineers (IEEE C37.2 Device Function Numbers and Contact Designations), namely the introduction of the use of acronyms, were opposed by some engineers, but survived the working group ballot process.

The twenty papers selected by the program committee were presented during five sessions. This is one of the few conferences that give enough t ime for a detailed presentation, followed by questions and discussions between the audience and the presenting industry experts.

The papers presented at the conference not only introduced some new developments and applications, but also delivered valuable concepts and information related to retrofitting substations, selecting the right communications topolog y and improving the engineering process.

The location of the exhibition area right next to the conference sessions room allowed the participants to use the coffee breaks and the time after the end of the paper sessions to see demonstrations of the latest hardware and software tools exhibited by leading manufacturers in the field of power delivery automation and communication networking technology.

The tenth Western Power Delivery Automation Conference was held from 6 April to 10 April, 2008 at the recently renovated Davenport hotel in the center of Spokane, WA. The conference was organized by Washington State University and is an annual event which focuses on the fast-changing issues of automation and control of electric power systems and substations. This two-and-a-half day conference is a gathering place for automation specialists interested in:

N e t w o r k P r o t o c o l s a n d Communications

Case Studies and Applications Security

Control and Automation LogicS C A D A a n d W i d e A r e a

Measurements E n g i n e e r i n g a n d P r o j e c t

ManagementThe conference started with

a keynote presentation by John Tengdin, OPUS Publishing, Life Fellow of IEEE. He talked about the fact that this year’s program bears little resemblance to that of 1999 or 2000. This is mainly because during these few years Ethernet in substations and with it IEC 61850 have come of age. This is proven by the nine papers in the conference program that include those topics in their titles. The focus is on the use of standards that are having significant impact on the design of new substation and power delivery automation systems. This is very timely, as five new or updated IEEE substation related standards have been approved in just the last year. The changes to the “language” of

Western Power Delivery Automation

Conference 2008

Paper session

during the

conference

The conference

was held at

the historical

Davenport

hotel

89

PAC.SPRING.2008

electric power systems protection, automation and control:

Tutorial Sessions Education Track Super Session Panel Sessions Poster Sessions Exhibitor Info Sessions

In parallel with the conference t h e a t t e n d e e s v i s i t e d t h e exhibition hall and discussed with participating experts the

latest solutions available to meet the requirements of utilities and industrial facilities.

Technical tours to the Twin Groves wind farm, Argonne National Laboratory, ComEd’s We st L oop sub st at ion and Operations Control Center (OCC) demonstrated real-life applications of advances technology.

The Conference Reception was held at the Museum of Science & Industry and gave the participants an opportunity not only to enjoy the exhibits, but also to network and exchange ideas about the future of our industry with colleagues from around the world.

IEEE PES T&D Conference

2008

The theme of the 2008

conference was “Powering

Toward the Future”.

The IEEE PES T & D Conference and Exposition was held in Chicago, Illinois from 21 to 24 April 2008. It brings together power-delivery professionals with many different areas of specialization, including transmission and distribution p l a n n i n g , p r o t e c t i o n a n d control, substation engineering, d i s t r i b u t i o n a u t o m a t i o n , communicat ions, renewable e n e r g y , o p e r a t i o n s , a n d maintenance. The McCormick Place was the conference venue. This conference provides a forum for discussions of a wide range of topics related to the present and future of our industry.

The technical program was designed to address the concerns of the industry and the impact of new technical and business solutions that support the operation and maintenance of the elec t r ic transmission and distribution system at peak levels, while maintaining the required reliability and security under maximum load and dynamic system conditions.

One of the goals of the conference was to help the industry with their need to educate young engineers in the fundamentals of electric power technologies and the applic at ion of new communications based intelligent devices and systems.

The conference program was divided in several different types of sessions, covering a wide range of topics, many related to

One of the goals of the conference was to help the industry with their need to educate young engineers.

The Conference

Reception was

held at the

Museum of

Science &

Industry

The McCormick Place was the conference

venue.

Become a PAC World correspondent:

Report on conferences, symposiums and exhibitions Conduct interviews with leading

industry experts Send information about system

events Capture with your camera the life of

our industry

To apply, send an e-mail to: editor@pacw.org

Yourphoto

phot

os o

f the

issu

e

91

Photo Competition 2008These photos were selected for the Spring 2008 issue.

They will be

considered for

the final Photo

of the Year

Competition.

Please, submit

your favorite

pictures for

Summer 2008.

Desert Mood Photo: Alexander Dierks/ South Africa/ Pentax Optio S5i

Good Morning Spring Photo: Kervin-Peng Yu/ China / Nikon D40X

PAC.SPRING.2008

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You never know who you are going to meet at a conference or exhibition. One thing is for sure – there will be many interesting people from our industry. But this time while I was attending the Western Power Delivery Automation Conference in Spokane, Washington I met someone who is not from our industry, but was drawn to the exhibition area in the Davenport hotel by his interest in electric power and all the issues related to it. Upon meeting him, he held in his hand a book, his book it turns out, Kilowatt, which is the subject of this review. It triggered an interesting conversation and I decided right then and there that I would find the time to review this book – even though it isn’t a technical book, but fiction.I think a quote from the web site http://www.readkilowatt.com/joe_mchugh.html describes the author quite well as “… a professional storyteller, public radio producer, playwright, museum director, festival organizer, old-time fiddler, educational consultant and home-grown philosopher. He regularly lectures on the art and practice of storytelling in the electronic age and has written two collections of folktales and humor and an illustrated children’s book about the early days of aviation.”

It is d i f f i c u l t t o define the category of the book, because it is multidimensional. On the surface it looks like a thriller, because we have a couple of ordinary people – two journalists from a small town radio station – trying to find the truth about a mysterious power plant in Texas that is making the employees sick. They are standing up against different villains – ruthless corporate executives and their cronies, corrupt politicians and the Russian mafia. At the same time the book is philosophical. The subject of time is directly related to the main plot, but it is also discussed from the point of view of our existence in time and how it changes depending on our state of mind. The book raises a lot of other questions (e.g. the meaning of “clean” power). We define things based on what we know, as well as our personal experience. Something that does not produce CO2 and radiation may look clean, but if it caused the sinking of a Soviet submarine – is it?This brings us to a different line in the story – the moral responsibility of the scientist while letting the Genie out of the bottle. Another difficulty with classifying

the book is due to the technology used to generate the power in the rural Texan plant. For us, as protection engineers, it is clear that such technology does not exist – so maybe this will make Kilowatt a science fiction book. Regardless of the fact that everything is happening here – on the planet Earth, and today – not somewhere in the future.It is impossible to talk about this 400 pages book in the limited space we have available here. But what is important to say, is that this is a very well written story that keeps you turning the pages trying to find the answers to the many questions that Joe McHugh raises:

How does the power plant work? What is the energy source? Who is going to win – Alice and

Reb or the villains? What happens to the inventor

of the technology? And many more...

Well, I am not going to tell you. You will have to read the book.

Kilowatt by Joe McHugh

Published by Calling Crane Publishing

ISBN # 978-0-9619943-4-1

KilowattA Novel

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by Benton Vandiver III, OMICRON, USA

A Tasty Hobby for Those with Patience

two friends and well, you know the rest. They set the time and place and all of a sudden you have a BBQ Cook-Off!

These have become so popular over the years that they are used most often for charity fund raisers and there’s an official organization that oversees the competitions, it’s the International Barbeque Cookers Association. (www.ibcabbq.org)

The Houston Livestock Show & Rodeo, (www.hlsr.com or http://www.hlsr.com/et/bbqc/bbqc_in-dex.aspx) is where they also host one the largest BBQ competitions in the state.

In 2008 the over 400 BBQ teams competed over two days and fed over 190,000 people coming to the cook-off & rodeo event. The amount of beef, chicken, pork, ribs, and other items that were cooked and consumed was staggering.

BBQ - a hobby?First, it’s not that unusual in

Houston to cook BBQ (over 300 restaurants) and second it’s down right popular as there are over 800 BBQ teams in the greater Houston area. A BBQ team is usually made up of a BBQ Pit, a ‘head cook”, and three to a hundred helpers. You might wonder how a hundred could actually cook, well they don’t actually but the logistics for a BBQ Cook-off Competition for a cor-porate sponsored team needs a big group.

A competition, you ask?Yes, that is one of the driving

forces for the popularity of BBQ in the state of Texas, plus the fun of participation. One guy says he can make the best tasting BBQ, and then someone else throws down the challenge. Next they each tell

I was asked by Alex

what hobbies I had, in

particular anything that

was out of the ordinary.

I related a few of them

to him and he zeroed in

on the barbeque (BBQ)

team that my wife I

participated on in the

Houston area.

Benton, the BBQ participant, shares with us some of his famous bar-beque recipes.

BiographyBenton Vandiver III received his BSEE from the University of

Houston in 1979.

He was with Houston Lighting & Power for 15 years and Multilin

Corp. for 4 years before joining OMICRON electronics where

he is currently Technical Director in Houston, TX. A Professional

Engineer, IEEE Member, and an active Z Krewe member (Galveston

Mardi Gras krewe), he mainly enjoys spending time with his wife

Julia and 2 year old daughter Jaclyn at every opportunity.

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PAC.SPRING.2008

So how did I end up on a BBQ team?

A close friend of ours asked for help about ten years ago when two of his team members (his sis-ter & her husband) could not help out. Julia and I said, “sure we’d be glad too, what time do you need us, where, and do I need to bring my Hi-bachi?” (a very small grill)

He replied, ”Be at Sam’s Grill & Bar parking lot on Friday at 3pm, we’ll be finished about 2pm on Sun-day. And here’s a picture of the ‘Pit’ we’ll use to cook on.” (see Figure 4)

BBQ organization:I first thought "what have I com-

mitted too?" Turns out a traditional BBQ Cook-Off requires a while to organize and execute.

The BBQ pit has to come up to temperature.

The fresh meats of each team have to be inspected and tagged by the judges to insure fairness in the competition, and it often takes twelve to fifteen hours to slow smoke a typical ten pound beef brisket till it’s done and ready to be served. (Ribs take five to six hours, chicken takes three to four hours.)

So the whole process becomes a forty-eight hour project manage-ment effort to coordinate the cook-ing of the four typical categories (sometimes as many as seven cate-gories) and have them at their tasty perfection precisely on the hour each one is required for submission to the judges.

And yes, this means all teams that are in the competition are do-ing the same thing.

So the larger the BBQ Cook-Off, the larger the logistics for the panel of judges to taste each team’s sub-mission and come to a decision on who’s is the best!

Once we participated in the first cook-off, we were hooked and en-joyed each opportunity to help the team. It’s actually hot hard work but you get used to it because it’s focused. You have a specific goal and known time to get it com-pleted. But at the same time there’s down time where you can visit and socialize with a great group of peo-ple with whom you build lasting relationships.

Over a few years our team deve-loped into an efficient workgroup where each person knew their tasks

and performed them like clock-work. Of course we had to have a team name, and ours was “Coyote Cookers”. (see CoyoteSign above) And in short order we had a run of success over a few years where we scored First Place in each category. (see awards in Figure 2)

We were lucky enough to pull it all together in a couple of com-petitions and place high enough to be the overall team winner twice. But the most memorable thing was our tag line, “We eat the best and submit the rest!” It was our way of saying that we couldn’t resist our own cooking and just couldn’t give it to the judges.

Many of the other teams agreed and we’d often have a large group over when the meats came off the pit. Our seven foot long pit was by no means large; some pits can be as big as an entire eighteen wheeler (over 38 feet long), but it’s enough to cook 14 briskets, 24 whole chi-ckens, 16 full slabs of ribs, and even a few pork loins. That’s enough to feed a group of 300 people when you add in the sides, like cole slaw, potato salad and ranch beans.

Later DevelopmentsAbout 4 years ago the team re-

tired, mainly because our “head cook” took this all way too seri-ously and opened a very successful

2 Some of the Coyote Cookers' awards for the four years of competitions

The BBQ team sign!

hobb

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PAC.SPRING.2008

BBQ catering business in Houston. So successful he “retired” from his day job and within six months was financially secure.

So there was something to our tag line and many in the Houston area benefited from the years of practice in those BBQ cook-offs. Ju-lia & I also came away with a lot of knowledge about cooking this way and what really made great BBQ.

Our favorite was and still is the BBQ Baby Back Ribs. (see Pit_wRibs in Figure 3) These were so good we would often cook up ex-tras to take home after the cook-off and feast for days. Then it wouldn’t be long before we were eagerly an-ticipating the next cook-off date.

We still see the old team from time to time and fire up the pit to relive those great weekends.

I learned that the old adage, “Good things come to those who wait” has a lot of truth to it.

For really good BBQ you have to be patient. If you are really pa-tient, you can learn a few cooking secrets. Each team develops their own style, but almost all do these as a minimum.

The Secret! Here’s THE cooking secret for

great BBQ anything. Get a Pit with a separate fire

box. Use real wood: oak for heat,

mesquite or hickory for its flavor, and Sassafras (or Cinnamon wood) for a great natural BBQ taste.

Keep the temperature be-tween 275 F and 350 F, 300 F be-ing optimum.

Make sure you’re producing enough smoke and never let flame touch the meat.

If you follow those guidelines, you can “BBQ” anything. Meats, fish, foul and even vegetables.

If you have a traditional BBQ with charcoal or propane, then fire up one side to 350 F and cook on the no fire side.

Use water soaked hickory wood chips if possible to help create some smoke, but indirect heat is better than you think.

Recipes for almost anything can be found on the web nowadays. Google “Texas BBQ Recipes” for some great sites and tips on Texas BBQ.

The Final Secret: "Rub" is the term for the spices

applied to the meats, it can be ei-ther wet or dry. Both can yield ex-cellent results. But it takes patience and experimentation to find that magic mixture that makes for a 1st Place Winner!

My motive for joining the

barbeque team was mainly for

entertainment,

but the good food could be a reason

for staying nine years with the Coyote

Cookers.

4 The Coyote Cooker when new

A Quality Pit of this type ranges from $3000 - $5000 USD.

3 Famous "Coyote" barbeque ribs

Barbeque pits use indi-

rect heat & smoke for

BBQ - the Texas way.

Try one of the recipes,

you will enjoy it!

Th

e A

rt o

f B

BQ

Coo

kin

g

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PAC.SPRING.2008

Here’s one of my favorites:

BBQ Whole Chicken

Prepare a fresh whole chicken by cleaning it thoroughly removing all internals, loose skin and loose fat, then washing it in cold water.

Pat it down with a paper towel but leave it moist. Then dry season it the way you normally like. As a suggestion: in a bowl, combine 3 tablespoons of black pep-

per, 1 teaspoon of garlic salt, 1 teaspoon of cayenne pepper and 2 table-spoons of any Italian seasoning. (Adjust ratios to taste if this is too strong for your pallet.) Mix thoroughly and then pat over entire outside of chicken. (we called this loving the chicken)

Take any remaining mix and shake inside the chicken to coat it. Now you need a canned beer, (no glass) we used Miller Lite or Bud

Light because we really want the water content, but I’ve used dark beers like a Guinness with good results too.

Open the beer and carefully shove it up the opening in the chicken (yes that’s it’s a$$) so that the chicken will “stand up” with the aid of the can.

Place it carefully on the grill and close the grill’s lid. Check it after 15-20 minutes and make sure it stays standing, the

beer will come to a slow boil and keeps the chicken moist from the inside.

Using indirect heat it will take about 2 hours to cook. During the process you can “glaze” the chicken with a BBQ sauce

if you wish but it really isn’t necessary. Practice a few times and you’ll find it makes a terrific entrée and a

conversation piece when entertaining your friends.

5 BBQ whole chicken - one of Benton's favorites

editor@pacw.org

If you or one of your

colleagues has an interesting

hobby, please let us know.

Send an e-mail with a brief

description to:

We eat the best

and submit the rest!

Coyote Cookers

1996-2005

last

wor

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cale

ndar

PAC.SPRING.2008

Your OpinionEvery quarter we post a question on the PAC World web site and ask you to select an answer that will help your colleagues from around the world un-derstand the trends in our industry.

The results from this non-scientific poll are shown in the chart to the right. As in the previous survey the number of people that decided to pick one of the four answers is relatively small – 166. I would like once again to say that it is not that difficult to take part in it, while by clicking on an answer that you select you will make an important contribution to our understanding of industry practices.If we analyze the result it is clear that one thirds of the participants prefer to use both relays of the same type and same manufacturer. The remaining three options are evenly distributed – at about 20% each.This is probably due to the fact that the decision for selection of redundant transmission line protection relays are based on many

different factors, such as economics, training, maintenance, protection philosophy, etc.

The new question on the web site is related to the main subject of the Spring 2008 issue – power systems analysis:What type analysis tools do you use related to protection and control?

The answers that you can choose from are:

Short circuit and protection coordination,

Electromagnetic transient simulation,

Both , None.

Please take a minute, go to the web site page and click on your choice. — Alex Apostolov

No clear preferenceFor three months we had on the PAC World web site a simple question:What redundant protection do you use on transmission lines?

The answers to the questions you can choose from and the percentage of responders that selected them are as follows:

Same type and same manufacturer: 34.9%

S ame t ype and different manufacturer: 23.5%

Different t ype and same manufacturer: 21.1%

Different type and different manufacturer: 20.5%

IX Spanish-American Electric Power Systems Protection Symposium 20-23 May 2008Monterrey, México, http://www.uanl-die.net/pages/sipsep.html

WINDPOWER 2008 Conference & Exhibition1 - 4 June 2008Houston, Texas http://www.windpowerexpo.org/

IX Technical Seminar on Protection and Control 1 - 5 June 2008Belo Horizonte-MG, Brazil http://www.ixstpc.com.br/paginas/default.asp

8th West African mining and power exhibition and conference 20083-5 June 2008 Accra, Ghana http://ems.mbendi.com/events/e4zj.htm

POWERGRID Europe3 - 5 June 2008 Milan, Italy http://pgrid08.events.pennnet.com/fl/home.cfm?Language=Engl EAA 2008 14–15 June 2008 Christchurch, New-Zealand

SmartGrids for Distribution seminar 23 - 24 June 2008Frankfurt, Germanyhttp://conferences.theiet.org/ciredsmartgrids/index.htm

IEEE RVP AI 6 - 12 July 2008Acapulco, Mexico 2008 IEEE PES General Meeting20-24 July 2008Pittsburgh, PA, USAhttp://ewh.ieee.org/cmte/PESGM08/

ACS Applied Control Systems Cyber Security Conference 4-7 August 2008 Chicago, IL , USA http://realtimeacs.com/?page_id=18

T&D Latin America 13-15 August 2008Bogota, Columbiahttp://www.ieee.org.co/tydla2008/

CIGRE Session 200824-29 August 2008Paris, Francehttp://conferences.theiet.org/ciredsmartgrids/index.htm

Poll Results: What redundant protection do you use on transmission lines?