Power System Relaying · Introduction The Power System Protection Philosophy Zone Protection / System Protection ... Modeling Symmetrical Components Three Phase/Asymmetric Faults/Fault

Power System Relaying – Deck 01

Copyright 1994-2020, A. P. Sakis Meliopoulos1.1

Power System Relaying

Theory and Application

ECE 6323

School of Electrical and Computer Engineering

Georgia Institute of Technology

Atlanta, Georgia 30332

Instructor:

Dr. A. P. Sakis Meliopoulos

Room 2447, Klaus Building



This course covers the theory, technology and practice of power system protection. It is intended to provide

students with the ability to understand modeling of power systems, fault analysis, stability analysis and a

wide range of protection functions and associated settings of protection functions. It will also discuss the

effects to protection systems of inverter interfaced generation and distributed energy resources in smart

grids. It will enable students to specialize in this important area of modern power systems.

Instructor: Dr. A. P. Meliopoulos

Office: E-164 VanLeer Building, Phone: 404 894-2926 (office)

e-mail: [email protected], [email protected]

Course WebSite : http://www.ap-concepts.com/ECE6323/

Office hours: MW 10:30 am - 12 noon, VanLeer 164

Help Hours: F 10:30 am – 12 noon, VanLeer 433

Textbook: Manuscript by A. P. Meliopoulos & George J. Cokkinides: “Power System Relaying: An

Introduction”. This book will be provided electronically.

References: W. A. Elmore, Editor, Protective Relaying: Theory and Applications, Marcel

Dekker/ABB, 1994

J. Lewis Blackburn, Protective Relaying: Principles and Applications, Marcel Dekker,

Second Edition 1998.

W. A. Elmore, W. J. Ackerman, E. Price, and L. Wang, Pilot Protective Relaying,

Marcel Dekker/ABB, 2000.

Glover and Sarma, Power System Analysis & Design, PWS Publishing Company,

1987 & 1994.

Selected technical papers.

mailto:[email protected]

mailto:[email protected]

http://www.ap-concepts.com/ECE6323/



Grading policy: Homework 20 %

Midterm Exam 25 %

Term Project 25 %

Final 30 %

Term Project: Project description have been posted on the

web site.



ECE6323 Course Outline

Introduction

The Power System

Protection Philosophy

Zone Protection / System Protection

Protective Equipment, Standards

Review of Background Material

Power System Modeling

Symmetrical Components

Three Phase/Asymmetric Faults/Fault Transients

Transformer In-Rush Currents

Motor Starting Transients

Effects of Grounding

High Impedance Faults

Grounding Potential Rise - Safety

Relaying Instrumentation

Instrument Transformers VTs, and CTs

Characteristic of VTs, and CTs

Optical VTs and CTs



Protection Fundamentals

Overcurrent Protection

Differential Protection

Overvoltage / Undervoltage Protection

Underfrequency / Overfrequency Protection

Zone Distance Protection

Pilot Relaying

Impact of inverter based generation

Protective Relaying Applications

Generator Protection

Motor Protection

Transformer Protection

Bus Protection

Line Protection - Network, Radial

Reactor and Shunt Capacitor Protection

Stability, Reclosing, and Load Shedding

Out-of-Step Relaying

Frequency and Voltage based load shedding

Special Protection Systems

Fundamentals of Automation

Objectives

Communication Standards, Interoperability

Applications, Integration of Substation Functions

Centralized Substation Protection, The Digital Substation



Protective Relaying Definition

The science, skill, and art of applying and setting relays

and/or fuses to provide maximum sensitivity to faults and

undesirable conditions, but to avoid their operation on all

permissible or tolerable conditions

L. Blackburn

Protection PhilosophyProtection Layers

- Protection Against Fast Transients

Surge Arresters, Inrush Current Limiters, Surge Capacitors, etc.

- Protection Against Long Disturbances

Protection Zones (Component Protection)

System Protection



The Power System• Faults – NC Faults - Under/Overvoltage – Swings – Other

• Protection Philosophies

• Phenomena Affecting Performance

Types of Relays• Protective

• Monitoring

• Reclosing

• Regulating

• Auxiliary

• Synchronizing

Technology• Electromechanical (1900s)

• Solid State (1960s)

• Digital/Numerical (PRODAR (1970), mP Based SEL (1984)) – Communications

• MU/Digital/Numerical with GPS Synchronization/Interoperability



Electromechanical RelaysPlunger Type, Induction Disk / Cup, Balancing Beam

1 2 3 4 85 6 10

0.51

3

45

67

89

10

2

Input Current in Multiples of Tap Setting

1

2

3

4

5

6

8

9

10

Relay Operating Time

(seconds)

Westinghouse

Plunger

Induction Disk

Induction Cup

Balancing Beam



Digital Relays

vc

vb

va Phase A

Phase B

Phase C

Power System

DAQ

Protection&

IsolationMicroprocessor

Displays

Software

CommunicationsStorage

Input Contacts

Ou

tpu

t Co

nta

cts

Clock

GPSAntenna

Time Stamping

Without GPS SynchronizationNote Clock is Connected to the

Computing Device



Digital Relays with PMU Capability

vc

vb

va Phase A

Phase B

Phase C

A/D Converter

( Modulation)

Input Protection &Isolation Section

OpticalIsolation

mP Mem

ory

PLL

Digitized Data2880 s/s

A/D Converter

( Modulation)

Input Protection &Isolation Section

OpticalIsolation

Sampling Clock

GPSReceiver

Digitized Data2880 s/s

1PPS IRIGB

GPSAntenna

DataConcentrator(PC)

Display&

Keyboard

RS232

MasterWorkstation

OpticalIsolation

OpticalIsolation

AnalogInputsV : 300VI : 2V

MACRODYNE PMU 1620 – Jan 1992

Jay MurphyPower System

DAQ

Protection&

IsolationMicroprocessor

Displays

Software

CommunicationsStorage

Input Contacts

Ou

tpu

t Co

nta

cts

Clock

GPSAntenna

GPS Synchronization

Note clock is connected

to the A/D Converter



Protective System Components

Interrupting Devices• Fuses

• Circuit Breakers

• Circuit Switchers

Supervisory and Control• Instrument Transformers

• Relays (Contacts)

Dis/Connecting Devices



Generic Structure of a Protective Relay

Best Source for

Specific Information:

Manufacturers

Literature

Legacy Relays

Merging

Unit(s)/Computing

Device Relay



Instrument Transformers

Voltage Transformers

• (Standard: 69.3 Volts, 115 Volts)

• PT

• CCVTs

• Vds

Current Transformers

• (Standard: 5 Amperes, 1 Ampere)

• CT/C

• CT/V

• Rogowski Coil

• (xxTyy or xxCyy, xx: max error, yy sec. voltage)

Optical Transducers

• Optical CT - MOCT

• Optical VT – EOVT

Non Conventional IT (NCIT)

sec

sec

:

:

primary n

primary n

Ideal s t r s t

Actual error s t r s t



Breaker Technology

• Oil Circuit Breaker

• Air Blast Circuit Breaker

• Vacuum

• SF6

Specifications

• Interrupting Capability – Duty Cycle

• Restrikes - TRV

• Maintenance



Zone Protection

• Generator

• Line

• Transformer

• Bus, etc.

Protection Problems

System Protection

• Out of Step (Transient Stability)

• Transient Voltage Collapse

• Load Shedding – Frequency-Based / Voltage-Based

• Special Protection Schemes



Zone Protection

Each Point in the System Belongs to

a Protection Zone

• Generators

• Transformers

• Buses

• Transmission Lines

• Motors

• Capacitor Banks

• Reactors, etc.

R

12kV

FDRZone

Radial

BusLine

230 kV20 kV

G+GSU Backup

Xfmr



System Protection

Load Shedding – Frequency-

Based / Voltage-Based

Out of Step (Transient Stability)

Transient Voltage Collapse

Special Protection Schemes

Illustration of Voltage Collapse Near the Center

of a Stable System Swing

Voltage Transitions Are Slow – Undervoltage

Protection Should not Operate

Illustration of Two Power System Swings:

(a)Stable – Out of Step Relay Should not Operate

(b)Unstable – Out of Step Relay Should Operate

Special Protection Schemes are Protective

Relaying Functions Concerned with the

Protection Against Special System Conditions

that May Lead to Catastrophic Results.

These System Conditions are Determined

with Extensive Studies of Specific System

Behavior. Using this Information a SPS is

designed to monitor the System and When

the Special System Conditions Occur

(Recognition/Triggers) the System Operates

(Automatically or with Operator Review and

Action)

A System Disturbance May Create Generation-Load Imbalance

Leading to Sustained Frequency Decline. This Condition, if not

Corrected, May Lead to Equipment Damage. The Condition Can be

Temporarily Corrected by Load Shedding Until Additional Generation

can be Dispatched.

Similarly, a Disturbance May Create Sustained Voltage Problems.

These problems Can be Also Corrected by Load Shedding



Objectives of Protective RelayingSafety, Safety, Safety

Avoid Equipment Damage

• Thermal

• Overvoltage

• Mechanical stress

• Over/Under Speeding

Load Conservation

• Stability

• Frequency (Gen-Load Balance)

• Synchronism

Protection Reliability

Dependability + Security

Selectivity

Speed

Economy Know the Power System




Reliability of Hardware (instrumentation, fuses, data

acquisition, computing devices, switches, cables, batteries,

communications media, etc.)

Reliability of protection scheme (protection functions, settings,

logic, controls, interlocks, etc.)



Definition of Protection ReliabilityHardware + Protection Scheme

Dependability:

“The degree of certainty that a relay system will operate correctly”

Security:

“The degree of certainty that a relay will not operate incorrectly”

Fa

il

Da

ng

ero

us

Fa

il S

afe




• Complexity of Modern Protection

Schemes

• Coordination of Protection Settings

• Real Time Monitoring of Relaying

Schemes

• Hidden Failures

• Equipment Failures

• Assessment of Protection Reliability



Unintended Relay OperationsInsecurity

• Incomplete Analysis of System Response

System Conditions Were not Predicted

• Load Encroachment

Design for near nominal voltages – what if

voltage sags during high loads for a relatively

long time?

• Transient Swings

May Cause Distance Relays to Operate on Zone 1

• Complexity of Present Day Relaying Schemes

Incorrect Logic, Incorrect coordination



Three Important Trends:

1. Relay Capability and Complexity is Rising

2. Industry Expertise is Retiring

3. Electric Power Programs in US Universities Minimized

Recipe for Relaying Unreliability

Thorough Review of Relay Settings

Computerized Procedures via Exhaustive Enumerations and Simulation of

Events (much more reliable than manually derived settings)

Monitoring of Protective System

Identification of Hidden Failures. Then what?

Addressing Protection Reliability

Simplification of Protective Relaying Settings

• EPRI/GT: Setting-less Protection (New Developments)

• EPRI/GT: Centralized Digital Substation Protection, self healing protection &

control (New Developments)



Are Present Day Tools Comprehensive Enough to Provide

100% Testing of Relay Settings?

How Much Expertise is Needed to Perform this Testing?

• Phasor Testing

• Testing with Disturbance Data

• Transient Testing (with simulated data)

• Synchronized Testing (87Line)

• Testing of GPS-Synchronized Relays

• Primary Injection Testing

• Virtual Relay Testing (CIGRE)

Thorough Review of Relay Settings

or

Protective Relaying Testing Methods



Yet… Performance Statistics: DoERelay Mis-operations: 10%

Of These 65% are related to hidden failures

Mis

op

era

tio

ns

5%

8%

8%

15%

29%

Total Hidden Failures: 65%



Sample StatisticsFor the Brazilian National Grid, the ISO collects yearly the data about the

performance of protection systems. The following table shows the

percentage of success in transmission line, transformer, and bus

protection, for the whole Brazilian electric power grid, in 3 years.

Year 2008 2009 2010

Line 97.42 96.3 96.8

Transformer 86.3 87.3 91.2

Bus 86.8 86.2 83.0



StatisticsProtection Systems Misoperations Identified as #1 NERC Reliability Issue in 2010



Abbreviations

NERC: North American Electric Reliability Corporation

FRCC: Florida Reliability Coordinating Council

MRO: Midwest Reliability Organization

NPCC: Northeast Power Coordinating Council

RFC: Reliability First Corporation

SERC: Southeastern Electric Reliability Council

SPPRE: Southwest Power Pool Regional Entity

TRE: Texas Reliability Entity

WECC: Western Electricity CoordinatingCouncil



High Fidelity Power System Simulator

• Physically Based Power System Modeling

• Explicit Representation of Phase Conductors, Neutrals, Ground

Conductors and Grounding – Accounts for ground potential rise

• Explicit Representation of Breakers, Switches and Relay Inputs

Integrated with the Power System

• Comprehensive Enumeration and Simulation of Possible Faults

and Disturbances

• Solver Based on the Quadratic Integration Method (free of

fictitious oscillations)

• Visualization and Animation of Relay Operation



Using Program WinIGS

Downloading Instructions



Comprehensive System Simulations to Cover All Possibilities

Examples



Comprehensive System Simulations to Cover All Possibilities

Examples

500 kV

230 kV

230 kV

500 kV

230 kV

230 kV



Know the Power SystemExample: Induction Effects

abc

If

500 kV

abc

230 kV

abc

230 kV



Standards and Books

• IEEE Std C37.2 – 1996, IEEE Standard Electrical Power System Device Function

Numbers and Contact Designations, Floyd W. Greenway, Chair, 1996.

• 95 TP 102, IEEE Tutorial on the Protection of Synchronous Generators, C. J. Mozina

Editor, 1995.

• Protective Relaying: Theory and Applications, Edited by Walter A. Elmore, Marcel Dekker,

Inc., 1994.

• J. Lewis Blackburn, Protective Relaying, Principles and Applications, Marcel Dekker Inc.,

1998

• Protective Relaying for Power Systems, Edited by Stanley H. Horowitz, IEEE Press, 1980

• Glover and Sarma, Power System Analysis & Design, PWS Publishing Company, 1987 &

1994

• C. Russell Mason, The Art and Science of Protective Relaying, John Wiley & Sons, Inc.,

1956

• Arun G. Phadke and James S. Thorp, Computer Relaying for Power Systems, Research

Studies Press Ltd., 1988.

• Vivian Cook, Analysis of Distance Protection, Research Studies Press Ltd., 1985.

• IEEE Std C37.113-1999, IEEE Guide for Protective Relay Applications to Transmission

Lines, W. Mark Carpenter, Chair, 1999.

• P. M. Anderson, Power System Protection, IEEE Press, 1999.

• C. R. Mason, The Art and Science of Protective Realying, John Wiley & Sons, Inc., 1956.



IEEE C37.2-1996 (1987)IEEE Standard Electrical Power System Device Function Numbers and Contact Designations

Device No. Device Description 1 Master Element

2 Time Delay Relay (starting or closing)

3 Checking or Interlocking Relay

4 Master Contactor

5 Stopping Device

6 Starting Circuit Breaker

7 Rate of Change

8 Control Power Disconnecting Device

9 Reversing Device

10 Unit Sequence Switch

11 Multifunction Device

12 Overspeed Device

13 Synchronous Speed Device

14 Underspeed Device

15 Speed or Frequency Matching Device

17 Shunting or Discharge Switch

18 Accelerating or Decelerating Device

19 Starting-to-Running Transition Switch

20 Electrically Operated Valve

21 Distance Relay

22 Equalizer Circuit Breaker

23 Temperature Control Device

24 Volts per Hertz Relay

25 Synchronoizing or Synchronism-Check Relay

26 Apparatus Thermal Device

27 Undervoltage Relay

28 Flame Detector

29 Isolating Contactor or Switch

30 Annunciator Relay

31 Separate Excitation Device

32 Directional Power Relay




Device No. Device Description 33 Position Switch

34 Master Sequence Device

35 Brush-Operating or Slip-Ring Short-Circuiting

36 Polarity or Polarizing Voltage Device

37 Undercurrent or Underpower Relay

38 Bearing Protective Device

39 Mechanical Condition Monitor

40 Field Relay

41 Field Circuit Device

42 Running Circuit Breaker

43 Manual Transfer or Selector Device

44 Unit Sequence Starting Relay

45 Atmospheric Condition Monitor

46 Reverse-Phase or Phase-Balance Current Relay

47 Phase-Sequence or Phase-Balance Voltage Relay

48 Incomplete Sequence Relay

49 Machine or Transformer Thermal Relay

50 Instantaneous Overcurrent Relay

51 AC Time Overcurrent Relay

52 AC Circuit Breaker

53 Exciter or DC Generator Relay

54 Turning Gear Engaging Device

55 Power Factor Relay

56 Field Application Relay

57 Short-Circuiting or Grounding Device

58 Rectification Failure Relay

59 Overvoltage Relay

60 Voltage or Current Balance Relay

61 Density Switch or Sensor

62 Time-Delay Stopping or Opening Relay

63 Pressure Switch




Device No. Device Description 64 Ground Detector Relay

65 Governor

66 Notching or Jogging Device

67 AC Directional Overcurrent Relay

68 Blocking or “Out-of-Step” Relay

69 Permissive Control Device

70 Rheostat

71 Level Switch

72 DC Circuit Breaker

73 Load-Resistor Contactor

74 Alarm Relay

75 Position Changing Mechanism

76 DC Overcurrent Relay

77 Telemetering Device

78 Phase-Angle Measuring Relay

79 Reclosing Relay

80 Flow Switch

81 Frequency Relay

82 DC Load-Measuring Reclosing Relay

83 Automatic Selective Control or Transfer Relay

84 Operating Mechanism

85 Carrier or Pilot Wire Relay

86 Lockout Relay

87 Differential Protective Relay

88 Auxiliary Motor or Motor Generator

89 Line Switch

90 Regulating Device

91 Voltage Directional Relay

92 Voltage and Power Directional Relay

93 Field-Changing Contactor

94 Tripping or Trip-Free Relay



Problem: Relay Mis-OperationsSolutions/trends: New Technologies

• Complexity

Relay Settings

Coordination Issues

• Data Integrity

• Hidden Failures

• Increased Inverter Interfaced Generation

• Cyber Attacks

• Protection Gaps

(HIF, Faults near neutrals, etc.)

• Unusual Events



Few Known Problems

• Mis-Coordination of Relays is a Major Contributor to

Relay Mis-operations

• How do we deal with the new reality of increasing

renewables e.g. Inverter Based Resources (IBR)?

How is the Protection and Control system affected?

Reduced fault currents from renewables (Inverters Limit Fault

Currents),

Different contributions of negative sequence/zero sequence

components effects on legacy protection? Performance of

directional elements?

• Need Protection Technology: Free of Coordination

and Immune to IBRs



Dynamic State Estimation Based

Protection

• Setting-less protective relay

• Sampled Value based dynamic

state estimation

• Fast fault detection (sub ms)

• Measurement of frequency

• Measurement of ROCOF

Analytics: Dynamic

State Estimation

(systematic way to

determine

observance of

physical laws)

DSE Motivation: In Search of

Secure Protection

Free of coordination and immune to IBRs



New Trends: The Digital

Substation Concept



To RHPP (3-0A0B1) Feeder 11

I

I

To RHPP (3-0A0B2) Feeder 12

II I

Feeder 8BFeeder 9BFeeder 10B

I

To East End (3-0B0D), Fdr 11

Yacht Haven Marina

P

T

S

I

Breaker 310

Bre

ake

r-303

Bre

ake

r 301

Bre

ake

r 309

T1

T2

P

T

S

Bre

ake

r 305

Bre

ake

r 307

Breaker 110

Bre

ake

r 115

Bre

ake

r 101

Bre

ake

r 109

Bre

ake

r 111

Bre

ake

r 113

Bre

ake

r 103

Bre

ake

r 105

Bre

ake

r 107

Yacht Haven MarinaFeeder 7B

I I

3-Ph-Fault=8.27, 8.25, 8.40 kAs

1-Ph-Fault=8.105 kAs

2-Ph-Fault=7.82 kAs

3-Ph-Fault=12.72, 12.65, 12.45 kAs



cal

LB102

AN

, B

N, C

N

LB002

A, B, C, N

LB001

LB_BF

LB87B1

LB104

LB87T1

LB103

AN, BN, CN

LB003

LB87B2

LB105

LB87T2

LB87B3

LB115

LB10B

LB7B LB_YH1 LB9B LB_YH2 LB8B

LB101

LB87B4

IED_ID

IED_ID

Client

3-0A0B

1

3-0A0B

2

3-0B0D

FDR-7

B

FDR-8

B

FDR-9

BFD

R-Y

H1

FDR-Y

H2

FDR10B

LB-T

1-1LB

-T1-3

LB-T

1-TLB

-T2-1

LB-T

2-3

LB-T

2-T

LB1-

01

LB1-

02

LB3-

01

LB3-

02

Present Automation in Protection and Control



Other Known Problems

• Is it necessary for each relay to be equipped with

data acquisition systems?

• Separation of data acquisition and protection

functions is today a reality.

• How is it used?



Separation of Data Acquisition and

Protection Functions

UGPSSM Merging Unit



Overall Approach

From

This

To

This



The Digital Substation Concept



Hybrid Substations



Centralized Substation Protection

Why and How

• Relays rely on (typically) three currents and three voltages.

What happens when inputs are compromised? Who can

provide supervision? How can inputs be corrected?

• What happens when hidden failures occur? Can present

technology detect hidden failures? Mixed answer at best!

• What happens when we have human error involved? Can we

detect wiring errors? Settings errors? Commissioning errors?

Historical performance: we are far away from 100%.

• What happens when an attacker gains access to the network

of relays and communications and have the ability to

manipulate data or issue trip and other control commands?



Dynamic

State

Estimation

Based

Centralized

Protection

Scheme

Resilient

Centralized

Substation

Protection

(rCSP)



ENDΤ

Λ

Ο

Σ



Long Term Objective / Vision

Next Generation Protection & Energy Management Systems

• Develop a New Approach and Method for Protection Based on Dynamic State

Estimation

(a) simplifies protection (setting-less protection)

(b) validated and high fidelity dynamic model of protection zone

• Make the Setting-less Relay the “Gate-Keeper” of Device Dynamic Models.

Relays are Ubiquitous 100% Coverage of System Model

• Setting-less Protective Relay Transmits the Validated Model Upstream

(substation, control center, enterprise, etc.): Models are available with minimum

latencies: Use Models for various Applications (as needed) in a seamless

process that is Free of Human Error

• Develop automated supervision of relays at substation-wide level:

• Verify merging unit/relay input data

• Detect hidden failures and take corrective actions

• Integrate detection of cyber attacks

Documents

Power System Relaying · Introduction The Power System Protection Philosophy Zone Protection / System Protection ... Modeling Symmetrical Components Three Phase/Asymmetric Faults/Fault