Crk Paper on Electric Power Quality

8/8/2019 Crk Paper on Electric Power Quality

1/30

ELECTRIC POWER QUALITY:SOME TECHNICAL AND COST

PERSPECTIVES

Dr. C.RADHAKRISHNA

Director,Global Energy Consulting Engineers Pvt. Ltd.

Hyderabad, A.P. , INDIA


2/30

INTRODUCTION

Maintaining good power quality has been a growing concern overyears. Earlier end users were mainly concerned about poweravailability, but the real quality of power has become a majorarea of concern for industry in recent years.

Though Power Quality is a term that means different things todifferent people, it all boils down to the objective of maintaining aset of electrical boundaries to allow a piece of equipment tofunction in its intended manner.

All power factor correction devices used in the industry, whichperform the role of Utility Interface are designed with the goal ofmaintaining the voltage waveform as close as possible to thesine wave and frequency.

Terms like "poor power quality" mean that there is ampledeviation from norms in the power supply that may causeequipment malfunction or premature failure.


3/30

INTRODUCTION contd..

As the sensitivity to such deviations varies from one equipmentto another, what may be considered poor power quality to onedevice may be perfectly acceptable power quality to another.

Electric power quality problems encompass a wide range ofdifferent phenomena with time scales range from tens ofnanoseconds to steady state. Each of these phenomena mayhave a variety of different causes and, thus, require differentsolutions that can be used to improve the power quality andequipment performance.

Many power quality (PQ) problems arise from the incompatibility

in the electrical environment between the utility supply systemand the equipment it serves. There are also PQ problems arisingfrom adverse interactions between the equipment and the supplysystem

Since PQ disturbances are relatively infrequent and the times atwhich they occur are unscheduled, continuous measurement or

monitoring over an extended period is often required.


4/30

PQ Monitoring

In addition to characterizing PQ problems, PQ monitoring hasbeen widely used to evaluate system-wide performance(benchmarking). By understanding the normal power qualityperformance of a system, a utility can identify abnormalcharacteristics and can offer information to customers to helpthem match their sensitive equipment characteristics with

realistic power quality characteristics. Since the time scales of PQ disturbances vary widely, power

monitoring instruments should ideally have the capability ofcapturing events ranging in frequencies from DC to a fewmegahertz.

As utilities and industrial customers have expanded their power

quality monitoring systems, the data management, analysis, andinterpretation functions have become the most significantchallenges in the overall power quality monitoring effort.

The shift in the use of power quality monitoring system from atraditional data acquisition system to a fully automated intelligentanalysis system would tremendously increase the value of powerquality monitoring.


5/30

POWER QUALITY PROBLEMS

It is important to be familiar with the most common and disruptivetypes of power quality problems and their typical solutions.

Harmonics are a distortion of the utility supplied waveform and arecaused by "non-linear" loads, which include motor controls,computers, office equipment, compact fluorescent lamps, light

dimmers, televisions and, in general, most electronic loads. Highharmonics increase line losses and decrease equipment lifetime.Total harmonic distortion (THD) measures the degree to which theinput is distorted, and is the relative value of all the harmonicscombined, as a percentage of the fundamental current.

Transients: Commonly called swells, surges and spikes, transients

are the most frequent types of power quality problems and often theeasiest to fix. The difficulty with transients is in detection since theymanifest only as a short-duration change in voltage.

Electrical noise is milder transient power irregularity that oftenmanifests as a computer glitch rather than an equipment failure.Essentially, electrical noise is created when one piece of equipment

interacts negatively with another, or with building grounding orwiring.


6/30

POWER QUALITY PROBLEMS contd..

Swells or Spikes can exceed normal voltage levels by 5 to 10 times enough to wipe out stored memory data and cause computeroutput, process and equipment errors, damage and failures. Low-energy swells are caused by the switching on and off of the electricmotors that power air conditioners, power tools, furnace ignitions,electrostatic copiers, arc welders and elevators. Larger swells are

usually caused by lightning. Sags (under-voltages) result when very large loads start up, or as a

result of a serious overload on the system.

Voltage Fluctuations: Left unchecked, high and low-voltageconditions can result in equipment damage, data loss and erroneousreadings on monitoring systems. Overloaded power circuits are

typically the cause behind under-voltage conditions. Brownouts are hours-long voltage sags caused by system

overload. U.S. utilities use rolling blackouts to avoid brownouts asbrownouts tend to damage equipment, but such fluctuations arecommon in developing countries.

Reliability refers to the probability of maintaining a continuoussupply of electricity without interruption.


7/30

SOURCES OF POWER QUALITY PROBLEMS

Recent studies conducted by the Edison Electrical Institute show

that 80 to 90 % of all power quality issues result from onsiteproblems, rather than utility problems. But, more importantly, thestudies indicate that power quality problems are on the rise forindustrial and commercial customers.

On their own, many of these problems may not have caused powerquality problems in the past. The recent proliferation of highly

sensitive computers, micro processor systems and powerelectronics in todays commercial and industrial equipment hasforever changed the nature of supply loading.

Ironically, new computer power supplies, adjustable speed drives,induction heating, arc furnaces and power conditioning equipmentemployed to improve productivity or solve power quality issues canoften become part of the problem, making power quality even moreof a mystery.

Among the types of equipment that both can cause power qualityproblems, and are susceptible to them, are: Uninterruptible PowerSupplies, Variable Frequency Drives, Battery Chargers, LargeMotors During Startup, Electronic Dimming Systems, LightingBallasts (esp. Electronic), Arc Welders, and Other Arc Devices,

Medical Equipment, e.g. MRIs and X-Ray Machines.


8/30

SOLVING POWER QUALITY

PROBLEMS The Institute of Electrical and Electronic Engineers (IEEE), various

government agencies and other organizations have issued designguidelines and recommended practices that are known to greatlyreduce, if not eliminate, the incidence and severity of power qualityrelated problems.

There are a variety of techniques that can help prevent or lessen theeffects of poor power quality. Most involve better electrical designsand installation of some additional wiring. These techniques areinexpensive to install, especially when a building is undergoingconstruction, and they may also be cost effective during retrofits.Consequences of poor power quality are much easier and cheaperto prevent than to diagnose and cure.

Here are some of the solutions for solving poor power quality problems.

Double-Size Neutrals, or Separate Neutrals per Phase: In most ofthe cases, harmonics can be easily handled by using double-sizeneutrals, as recommended by the IT Industry Council. Alternatively,separate neutrals can be used for each phase conductor. The

additional cost of over-sizing the neutral is minimal.


9/30


PROBLEMS contd. Harmonic Filters: Filters are sometimes most cost effective in an existing

structure where rewiring is difficult or costly. But the filter design is dependent onthe equipment on which it is installed, and may be ineffective if the particularpiece of equipment is changed. Filtering characteristics need to be carefullydesigned for a given installation.

Shielded Isolation Transformers: Shielded isolation transformers are filtering

devices that lessen feed-through of harmonic frequencies from the source or theload. They are a plausible retrofit technique where power problems have alreadybeen encountered.

K-Rated Transformers: K-rated transformers have beefed-up conductors andsometimes cooling to safely handle harmonic loads. Alternatively, standardtransformers are sometimes de-rated (up to 50%) to allow for the extra heatingdue to harmonics. A careful comparison of the relative costs of K-rated vs.

derated standard transformers should be made. Harmonic-Rated Circuit Breakers and Panels: Overheating due to harmonics

is the danger here, and beefed-up components used in these elements offerprotection. Neutral buses should be rated for double the phase current.

Separation of Sensitive Electronic Loads From Other Equipment: Adedicated "computer" circuit in each office is a good idea, at least back to thebranch circuit panel. A dedicated circuit means separate phase wires, a

separate neutral, with a separate grounding conductor, run in its own separatemetal conduit, back to the source.


10/30


PROBLEMS contd. Limited Number of Outlets per Circuit: Three to six outlets per circuit is recommended.

This will minimize the number and variety of sensitive equipment sharing circuitry, tend tominimize voltage drop, minimize the chance for interaction, and leave some room for latergrowth or equipment changes.

Metal Conduit: Metal conduit, properly grounded, provides shielding of the conductorsfrom RF energy. However, do not omit the grounding conductor , irrespective of the conduitmaterial. It is needed for safety, as well as assurance of a continuous, low impedance path

to ground. The grounding conductor is run inside the metal conduit, not outside. Voltage Drop: Although, normally, Standards allow up to a 3% voltage drop in a branch

circuit, recommended practice is to design for no more than a 1% voltage drop at full loadon branch circuits feeding sensitive equipment..

Isolated Grounds (IG): Isolated grounding is a loosely defined technique that attempts toreduce the chances of "noise" entering the sensitive equipment through the equipmentgrounding conductor. One may consider installing the IG conductor, to be available ifneeded, but experiment with reverting to a solidly grounded method if proven superior.

Ground Rings: A buried exterior ground ring is a technique to help achieve a lowimpedance from the building's grounding system to the earth itself, and a convenientmeans to connect various grounds leading from the building. For what has been estimatedas an extra 1-2% of the cost of construction, they are assured that the electrical system willserve their needs into the future, without the need for excavation or other costly retrofitsthat can be prohibitively expensive in urban setting.

Lightning Protection Systems: Lightning produces very high currents, for a short timeinterval, but enough to cause fires or to destroy microcircuits even miles away. The

purpose of air terminals or lightning rods is to provide a convenient, controlled point forlightning to strike, and then be safely conducted to ground.


11/30

POWER QUALITY AUDIT The objective of power quality audit is to determine the source of power quality

problems and to devise a solution to that problem. Prior to conducting a power quality audit, energy managers should look at a facility's

unique power needs and then budget appropriately. For instance, what kind ofmonitoring and control equipment is really needed? Super-fast equipment that cancapture events to the millisecond may not always be necessary if no plant equipmentis that sensitive. At other plants, however, sensitivity is essential.

During the audit, monitoring devices are placed throughout the facility in order todetermine precisely where in the system power quality problems are being found, aswell as to monitor the quality of the power being supplied by the electric utility.Typically, after two to three weeks of monitoring, the power quality professional hasenough data to recommend ways to solve any power quality problems.

Basic data gathering and analysis typically takes no more than a few weeks. Afterthat, it really depends entirely on the extent of the problem and how simple orcomplex the method may be to get everything up and running. The monitoringsystems themselves are very maintenance free and very robust.

Web based power quality monitoring is becoming increasingly popular. For instance,Automated Energy, Inc. in Oklahoma City, offers Internet-based Energy InformationManagement Services, which include a complete power quality solution. They provideservices and metering apparatus to monitor, record, analyze, and respond to powerquality problems, which can help pinpoint the source of problems, avoiding serviceinterruption and protecting equipment. They can monitor systems 24 x 7 andautomatically notify the customer of problems via Internet, or email.

So while power quality issues may be on the rise, it's becoming clear that energy

managers also have an increasing number of solutions at hand.


12/30

UTILITY POWER QUALITY

SERVICES

1. Services to help avoid power quality problems at theplanning/design stage: It is always best to avoid power quality

problems before they occur. This can be accomplished byunderstanding the environment, developing equipmentspecifications for compatibility, and designing facilities to allowconvenient power conditioning for critical and sensitive equipment.

2. Services to help solve power quality problems: These servicesare designed to assist in understanding the causes of problems and

developing optimum solutions. The services can include theinvestigations, recommending solutions, and actually implementingsolutions.

3. Services to verify performance and provide ongoinginformation: Information services can help customers identifyequipment problems quickly, characterize problems when theyoccur, verify the proper operation of power conditioning equipment,

and provide the basis for future equipment specifications.

Some of the utilities offer their customers, services in area of power quality as

part of value added services. Power quality services fall into three major

categories:


13/30

Unbundling Power Quality

Services One of the driving forces behind change in the power industry has beencustomers seeking variety in terms and conditions of electric service.

In the past to the electrical power user power quality implied that power wasavailable when needed at an acceptable voltage level. Today the definitionof power quality depends on the users load and its sensitivity to voltagechanges. These changes are a result of the introduction of equipmentbased on adjustable speed drives (ASD) and complex control systems.

There a many forces encouraging change in the distribution system. Theseinclude new marketplace opportunities, change in the character ofcustomers load and the need for power quality services.

From the user perspective, power disturbances that once were barelynoticed now produce costly malfunctions in customers equipment. This

change in the nature of the load demands more flexibility in power qualityservices.

Risk management is not only a hedge against the cost of power, butprotection against costly loss of production due to a short or long loss ofpower.

These technological changes suggest the possibility of an integrated,

customer centered electrical energy supplier which has the ability toprovide extra user services in addition to low cost power.


14/30

Unbundling Power Quality

Services contd.. Today's power electronic technology enables the supplier to providedifferent levels of power quality to the end user at a cost reflecting the users

needs. For example, premium power to the sensitive loads would warranthigher tariffs than a thermal load that is willing to lose service in exchangefor lower energy costs. This ability to provide a range of quality of power isbecoming a distinct competitive advantage as utilities face increasingcompetition through deregulation of retail markets.

When power electronics are brought to bear, the primary features is fastsub-cycle control.

A SolidState BreakerSSB can be used to isolate a faulted feeder in lessthan a cycle, thereby avoiding a sag on adjacent feeders.

If parallel feeders are available to a load, a Solid State Transfer SwitchSSTS can provide an instantaneous transfer between feeders, decreasingthe likelihood of a complete outage or transferring the load away from a

sagging feeder.

A Static Var Compensation SVC can compensate for the effect of widelyvarying loads.

A Battery Energy Storage System BESS can be used to providecompletely uninterruptible power.

For removing sags at a customers bus, the Dynamic Voltage Restorer

DVR and the Static Compensator STATCOM are the most appropriatedevices.


15/30

HARMONICS AND POWER

FACTOR We are all familiar with power factor, but are we using it to its

true potential?

Here we investigate the effect of harmonics on power factorand show through examples why it is important to use true

power factor, rather than the conventional 50/60Hzdisplacement power factor, when describing nonlinear loads.

Voltage and current harmonics produced by nonlinear loadsincrease power losses and, therefore, have a negative impacton electric utility distribution systems and components.

While the exact relationship between harmonics and losses isvery complex and difficult to generalize, the well establishedconcept of power factor does provide some measure of therelationship, and it is useful when comparing the relativeimpacts of nonlinear loadsproviding that harmonics areincorporated into the power factor definition.


16/30

Power Factor in Non-sinusoidal

Situations Now, consider non-sinusoidal situations, wherenetwork voltages and currents contain harmonics.While some harmonics are caused by systemnonlinearities such as transformer saturation, most

harmonics are produced by power electronic loadssuch as adjustable-speed drives and diode bridgerectifiers. The significant harmonics (above thefundamental, i.e., the first harmonic) are usually the3rd, 5th, and 7th multiples of 50/60 Hz, so that the

frequencies of interest in harmonics studies are inthe low-audible range.

When steady-state harmonics are present, voltagesand currents may be represented by Fourier seriesof the form


17/30

It is important to point out that one cannot, in general,compensate for poor distortion power factor by adding shuntcapacitors.

Only the displacement power factor can be improved withcapacitors.

This fact is especially important in load areas that aredominated by single-phase power electronic loads, which tendto have high displacement power factors but low distortionpower factors.

In these instances, the addition of shunt capacitors will likelyworsen the power factor by inducing resonances and higherharmonic levels.

A better solution is to add passive or active filters to removethe harmonics produced by the nonlinear loads, or to utilizelow-distortion power electronic loads.

Power factor measurements for some common single-phaseresidential loads are given in Table 1, where it is seen thattheir current distortion levels tend to fall into the followingthree categories: low (THDI


18/30

Table 1: Power Factor and CurrentDistortion Measurements for Common

Single-Phase Residential Loads


19/30

HARMONIC LOAD FLOW

Modeling of Loads Consumers' loads play a very important part in the harmonic network characteristic.

They constitute not only the main element of the damping component, but may affectthe resonance conditions, particularly at higher frequencies. Indeed, measurementshave shown that maximum plant conditions resulted in a lowering of the impedance atthe lower frequencies, but cause an increase at higher frequencies. Simulations haveshown that the addition of load can result in either an increase or decrease inharmonic flow. Consequently, an adequate representation of the system loads is

needed. However, it is very hard to obtain detailed information about this. Moreover,as the general loads consist of an aggregate number of components, it is difficult toestablish a model based on theoretical analysis.

Attempts to deduce a model from measurements have been made. However, morecomprehensive measurements and system data are needed.

Although practical experience is still insufficient to guarantee the best model, systemstudies have to proceed with whatever information is available. Thus, loadcharacteristics are looked at in detail and alternative models are required to be

developed.

A typical composition of consumers' plant may be as shown in Table. From theTable, it seems evident that there are basically two sorts of linear loads -- resistiveand motive. That would imply a simple combination of resistances and inductances.However, the difficulty in obtaining detailed information about composition, power andvariation with time makes the task very hard.

Nevertheless, it is possible to approach the problem of representing loads for

harmonic studies by using alternative models according to the load characteristicsand information available.


20/30

TABLE: Load Composition

(*)These loads are harmonicproducing. Hence, they do not

exhibit a constant R, L, or C,

i.e.. they are non-linear and

therefore cannot be included in

an equivalent network of

impedances. Fortunately, thereis every reason to believe they

have insignificant effect (open

circuit) on the harmonic

impedance.

Nature Type of Load Electrical Characteristics

Domestic Incandescent Lamp Passive Resistive

Compact Fluorescent Non-linear

Small Motors

Computers Passive Inductive

Home Electronics Non-linear (*)

Non-linear(*)

Commercial Incandescent Lamp Passive Resistive

Air Conditioner Passive Inductive

Resistive Heater Passive Resistive

Refrigeration Passive Inductive

Washing Machine Passive Inductive

Fluorescent Lamp Non-linear(*)

ASDs Non-linear(*)

Fluorescent (Electronics) Non-linear(*)

Computers Non-linear(*)

Other Elect. Loads Non-linear( *)

Non-linear(*)

Small industrial Plants Fan Passive Inductive

(Low Voltage) Pump Passive Inductive

Compressor Passive Inductive

Resistive Heater Passive Resistive

Arc Furnace Non-linear(*)

ASDs Non-linear(*)

Other Electronic Loads Non-linear(*)


21/30

In the last few years, there has been a growing interest inobtaining steady state network voltages at harmonicfrequencies due to the increase of nonlinear devices in

electric power networks. The procedures for analyzing the harmonic problem could be

classified into frequency domain and time domain.

Frequency domain methods are the most widely used for theharmonic problem formulation. They are a reformulation of the

conventional load flow in order to include the nonlinear devicetreatment and the calculation of harmonic voltages.

The recent appearance of nonlinear devices (NLD) in theEPS provoked harmonic distortion in the network voltages.This fact and the increasing number of applications with NLDhas led us to analyze the steady state harmonic problem.

Conventional Load Flow (CLF) must be replaced to calculatethe following starting from CLF and NLD behavior data:

the fundamental bus voltages;

the harmonic bus voltages;

the parameters which characterize the NLD state.


22/30

A. Harmonic Penetration:

The first and simplest method is harmonic penetration (HP) , whichassumes no harmonic interaction between network and NLD (i.e., itconsiders that harmonic voltages have no influence on the NLD

behavior). The no interaction hypothesis allows the NLD treatmentto be approached considering the fundamental voltages and NLDdata dependence, thus facilitating their incorporation to the CLF.

B. Iterative Harmonic Penetration:

Iterative harmonic penetration (IHP) is the first modification from theHP which takes into consideration harmonic influence on NLD

behavior.C. Simplified Harmonic Load Flow:

Iterative techniques between both formulations are necessary tosolve the harmonic problem. This idea is developed and improvedin the simplified harmonic load flow. A fixed-point iteration of two NRprocedures is used: one for CLF and the other for harmonic

analysis (HA)

D. Complete Harmonic Load Flow:

Originally, a reformulation of the CLF in order to include NLD wasimplemented. This formulation is a natural modification of the CLFwhere the NLD treatment and the harmonic voltage calculation havebeen included. It is based on the simultaneous resolution of powerconstraints, harmonic current balance, and NLD equations.


23/30

Harmonic Penetration Analysis

Often called current source methods

Assume that load harmonic currents are

known Magnitude only

Magnitude and angle

Source(s) of data

Manufacturers (magnitude only)

Measurements (magnitude and angle)


24/30

Harmonic Penetration Analysis(How the method works)

Step 1: Study the harmonic current data. Whichfrequencies are present?

Step 2: Build [Y] model for these frequencies

Taking R(w), L(w), and C(w) into account

Taking Z=R+jwL and Z=1/jwC into account

Step 3: Build I vector for each frequency

Most entries nonzero for f0

Various patterns of zero/nonzero entries for fh,h{1

Step 4: Solve for V vector for each frequency

Superposition allows construction of voltageFourier series


25/30

Power Quality as an

Educational Opportunity

It seemingly has been the philosophy in PowerEngineering to design power distribution systems thatcan accept almost any load almost at any time. Thedesign and operation of power distribution systemsrequire education of users and distribution engineersalike so that loads do not present an insurmountablechallenge to the power distribution system.

The educational issue is that power engineers must be

familiar with basic power quality concepts. Theexpectation is that with inclusion of power qualityengineering into under-graduate and graduate studies,engineers on both sides of the meter would besensitized to uphold high levels of power quality.


26/30

Analysis Methods The applications in power engineering for transient

analysis and propagation of harmonic signals shouldbe reinforced in the educational program. The conceptof a Fourier series is essential in explaining

harmonics. Analysis of harmonics propagating in a power

distribution or transmission system can be performedutilizing a range software packages, many of whichprovide convenient graphic output that may be

compared to company and industry-wide standards.

Another area in power quality engineering building onstudents engineering skills is the study of non-repeating events that degrade power quality.


27/30

Power Quality Standards

Some coordination of PQ requirements between customers, utilities, andequipment manufacturers is necessary to ensure satisfactory delivery ofelectrical energy.

Engineers designing equipment to be connected to a network need to beaware of the applicable standards and the requirements which they impose.

The benefit to the student is the opportunity presented to obtain practice inan engineering skill without the risk of adverse consequences to society.

A power quality course focusing heavily on harmonics can includediscussion on harmonic guides such as IEEE 519 and IEC/TR 61000-3-6.

Students can be introduced to the notion of standards that are based uponexperience rather than theory. Also for consideration is the need to beaware of methods and their limitations.

Estimates of the costs of PQ problems vary widely. Techniques forattributing costs to individual connected entities are not well established.

Given the tendency towards deregulation of the electricity industry, it islikely that regulatory bodies, utilities, and other stakeholders will exploreoptions for market-based power quality cost infrastructures. Thus, powerquality offers the opportunity to bring basic concepts in cost-to-benefit

analysis to the class-room.


28/30

Curricular Issues & Laboratory

Work

Causes, effects, and mitigation methods of

common power quality disturbances can be

readily demonstrated both in an under-

graduate laboratory and via simulationpackages such as PSCAD/EMTDC and

ATP-EMTP.

Power Quality concepts are motivational tostudents and build on students capabilities in

signal processing and power engineering.


29/30

REFERENCES

[1] Roman Targosz : End use perceptions of Power Quality: A EuropeanPerspective, EPRI Power Quality Applications(PQA) and AdvancedDistribution Automation(ADA) 2007, Joint Conference and Exhibition,June 2007.

[2] G.T.Heydt : Contemporary Topics in Electric Power Quality, Arizona

State University, PSERC Tutorial.

[3] S.Mark Halpin, Paulo F. Ribeiro, and J.J.Dai : Frequency Domain Analysis Techniques, Chapter 7, Harmonics Modeling & SimulationTutorial.

[4] Gary W.Chang : Harmonics Theory, Siemens Power Transmission &Distribution.

[5] M.Brent Hughes and Allen Stanbury : Harmonics, Metering and IEEEStd. 1459.

[6] M.F.McGranaghan and Surya Santoso : Challenges and Trends in Analyses of Electric Power Quality Measurement Data, EURASIPJournal on Advances in Signal Processing Volume 2007, Hindawi

Publishing Corporation.


30/30

[7] W.Mack Grady and R.J.Gilleskie : Harmonics and how they relate toPower Factor , Proc. of EPRI Power Quality Issues & OpportunitiesConference.

[8] Paulo F. Ribeiro : Modeling of Power System Components : DistributionSystem, Loads and other Elements Modeling , Chapter 3, Tutorial onHarmonics Modeling and Simulation, IEEE PES Winter Meeting 1998.

[9] Rahul Walawalkar, Vaidyanath Iyer and Madhusudan Murthy : UtilityInterface and Power Quality: The Flip Side.

[10] (Edited by) Francois Martzloff, Thomas Key, Arshad Mansoor, andE.Yandek: pq Commentary: The Power Quality Implications of

Conservation Voltage Reduction, EPRI PEAC, 2001.

[11] Erich W.Gunther, and M.F.McGranaghan : Power Measurements inDistorted and Unbalanced Conditions: An overview of IEEE Trial-useStandard 1459 2000, IEEE, 2002.

[12] R.Lasseter and C.Hochgraf : Unbundling Power Quality Services :Technical Issues, Proc. of the Thirtieth Annual Hawwaii InternationalConference on System Sciences, IEEE Computer Society, 1997.

[13] Timothy J. Browne and Gerald T. Heydt : Power Quality as anEducational Opportunity, IEEE Transactions on Power Systems, vol.23,no. 2, May 2008.

Documents

Crk Paper on Electric Power Quality