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412 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 43, NO. 2, MARCH/APRIL 2007

Roadmap for Power-Quality Standards DevelopmentDavid B. Vannoy, Member, IEEE, Mark F. McGranaghan, Senior Member, IEEE, S. Mark Halpin, Fellow, IEEE,

W. A. Moncrief, Senior Member, IEEE, and D. Daniel Sabin, Senior Member, IEEE

AbstractPower-quality (PQ) standards provide the basis forachieving compatibility between the characteristics of the electricsupply system and end-use equipment. They provide the methodsfor evaluating performance, define equipment requirements, andoutline relative responsibilities. This paper describes the statusof important PQ standards around the world and presents aroadmap for ongoing standards development.

Index TermsFlicker, harmonics, power quality (PQ), stan-dards, transients, voltage sags, voltage unbalance.

I. INTRODUCTION

THE REQUIREMENTS of electricity customers have

changed tremendously over the years. Equipment has

become much more sensitive to power-quality (PQ) variations

and some types of equipment can be the cause of PQ problems.

Standards are needed to achieve coordination between the

characteristics of the power supply system and the requirements

of the end-use equipment. This is the role of PQ standards.

During the past 15 years, much progress has been made in

defining PQ phenomena and their effects on electrical and elec-

tronic equipment. In addition, methods have been established

for measuring these phenomena and in some cases defining

limits for satisfactory performance of both the power system

and connected equipment. In the international community, both

IEEE and International Electrotechnical Commission (IEC)have created a group of standards that addresses these issues

from a variety of perspectives. However, there is a continuous

need to define coordination requirements, methods of assessing

performance, and relative responsibilities.

The IEEE Standards Coordinating Committee on Power

Quality (SCC22) tracks the development of PQ standards and

has created a master plan to direct standards development

efforts in needed areas. In addition, SCC22 has a focus on

continuing efforts to coordinate international PQ standards to

Paper PID-06-21, presented at the 2005 IEEE Petroleum and ChemicalIndustry Technical Conference, Denver, CO, September 1214, and approved

for publication in the IEEE TRANSACTIONS ON INDUSTRY APPLICATIONSby the Petroleum and Chemical Industry Committee of the IEEE IndustryApplications Society. Manuscript submitted for review September 15, 2005 andreleased for publication October 5, 2006.

D. B. Vannoy, deceased, was with Vannoy Consulting, Wilmington,DE 19808 USA.

M. F. McGranaghan is with EPRI Solutions, Knoxville, TN 37932-3723USA (e-mail: [email protected]).

S. M. Halpinis with theDepartment of Electrical andComputer Engineering,Auburn University, Auburn, AL 36849 USA (e-mail: [email protected]).

W. A. Moncrief is with Hood-Patterson & Dewar, Norcross, GA 30071 USA(e-mail: [email protected]).

D. D. Sabin is with EPRI Solutions, Beverly, MA 01915-6107 USA (e-mail:[email protected]).

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TIA.2006.890017

provide consistent requirements and evaluation methods around

the world. This paper examines existing IEEE and IEC stan-

dards and describes the need for ongoing development.

II. ROLE OF PQ STANDARDS

PQ problems ultimately impact the end user. However, there

are many other parties involved in creating, propagating, and

solving PQ problems. PQ standards must provide guidelines,

recommendations, and limits to help assure compatibility be-

tween end-use equipment and the system where it is applied.

The following are basic needs for PQ standards.

1) Definitions, Indexes. Standards are needed to define the

indexes that are used to characterize performance and

provide definitions for important PQ characteristics.

2) Measurement and monitoring procedures. Standard-

ized methods of characterizing performance and evalu-

ating equipment characteristics are needed.

3) Benchmarking. Understanding expected PQ characteris-

tics for different types of systems provides the basis for

establishing guidelines and limits.

4) PQ Guidelines and Limits. These standards provide

the Compatibility Levels that define the expected PQ

levels. They need to be defined in three categories:

1) PQ requirements for the supply system;2) PQ immunity for equipment;

3) PQ disturbance generation limits for equipment and

end-user systems.

5) Application guidelines. Finally, the standards need to

provide guidance in controlling PQ and solving problems,

including methods to understand the economics of solv-

ing PQ issues at different levels.

III. PQ STANDARDS DEVELOPMENT ORGANIZATIONS

The IEC is the main organization responsible for PQ

standards development in the international community. IECstandards are often adopted by individual countries as actual

performance requirements. IEEE also has a number of impor-

tant standards development activities in the PQ area and is

actively coordinating with the IEC Working Groups that are

primarily responsible for PQ standards.

The IEC has defined a category of standards called Elec-

tromagnetic Compatibility Standards that deal with PQ issues.

They fall into the following six categories.

1) General. These provide definitions, terminology, etc.

(IEC 61000-1-x).

2) Environment. Characteristics of the environment where

equipment will be applied (61000-2-x).

0093-9994/$25.00 2007 IEEE


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VANNOY et al.: ROADMAP FOR POWER-QUALITY STANDARDS DEVELOPMENT 413

3) Limits. Emission limits define the allowable levels of

disturbances that can be caused by equipment connected

to the power system. These standards were formerly the

IEC 555 series but now are numbered 61000-3-x. For

instance, IEC 555-2 has now become IEC 61000-3-2.

4) Testing and Measurement Techniques. These provide

detailed guidelines for measurement equipment and testprocedures to assure compliance with the other parts of

the standards (61000-4-x).

5) Installation and Mitigation Guidelines. These are de-

signed to provide guidance in application of equipment,

such as filters, power conditioning equipment, surge sup-

pressors, etc., to solve PQ problems (61000-5-x).

6) Generic and Product Standards. These will define im-

munity levels required for equipment in general cate-

gories or for specific types of equipment (61000-6-x).

The following working groups of IEC SC77A are actively

developing these standards.

1) Working Group 1Harmonics and other Low-frequencyDisturbances. Focus on limits and methods of measure-

ment for harmonics and interharmonics.

2) Working Group 2Voltage Fluctuations (flicker) and

other Low-Frequency Disturbances. Develops limits for

voltage fluctuations caused by end-user equipment and

methods of measurement as appropriate. This working

group will be working on an update to the document on

reference impedances that can be used for evaluating the

impact of equipment on the system.

3) Working Group 6Low-Frequency Immunity Tests. De-

velops testing procedures for evaluating equipment im-

munity from PQ variations.4) Working Group 8Electromagnetic Interference Related

to the Network Frequency. This group is addressing the

full range of PQ phenomena on the network and the

interaction issues with consumers.

5) Working Group 9PQ Measurement Methods. Cur-

rently, developing IEC 61000-4-30, an overall guide

defining the requirements for PQ monitoring equipment.

In the United States, standards are developed by the IEEE,

American National Standards Institute (ANSI), and equipment

manufacturer organizations, such as the National Electric Man-

ufacturing Association. There are also safety-related standards,

like the National Electrical Code. IEEE standards generally donot specify requirements for equipment. These standards tend

to be more application oriented, like IEEE Standard 519-1992,

which provides recommendations to limit harmonic distortion

levels on the overall power system.

The SCC22 was created in 1991 as a coordinating body

for PQ standards in IEEE. Historically this committee met at

both Power Engineering Society meetings and the Industry

Application Society Annual Meeting to help coordinate the

standards activities under way in each of these societies. In

addition, SCC22 sponsored standards efforts when no Society

Committee sponsor was available. Recently, a Power Quality

Subcommittee was created under the Transmission and Distri-

bution Committee of the Power Engineering Society to sponsorindividual working groups and task forces that are developing

Fig. 1. Concept of compatibility level defining steady-state PQ characteristicsthat results in compatibility between supply system and end-use equipment.

standards. Ownership for several of the SCC22 sponsored

standards Working Groups was transferred to this new Sub-

committee. This new subcommittee coordinates closely with

SCC 22. SCC22 membership is composed of persons activelyinvolved in PQ standards development and represents a variety

of industry segments.

A listing of some of the important PQ standards activities in

IEEE is provided in the Appendix.

IV. STEADY-S TATE PQ CHARACTERISTICS

PQ characteristics and requirements are divided into two

broad categoriessteady-state, or continuous, characteristics

and disturbances. Steady-state characteristics define the re-

quirements for the normal voltage supplied from the power

system and the relative responsibilities of the supply system andend users and equipment in maintaining the required quality of

the voltage. Disturbances, on the other hand, occur randomly

and different methods of describing performance and coordina-

tion requirements are needed.

For steady-state PQ characteristics (voltage regulation, un-

balance, harmonics, flicker), the levels on the supply system

are coordinated with the characteristics of equipment to define

compatibility levels. Steady-state characteristics are character-

ized with trends and statistical distributions of the quantity

being evaluated. Understanding that these characteristics are

not defined with a single value but represent a range of values

with a probability distribution is very important. The concept is

illustrated in Fig. 1.The concept of compatibility levels in Fig. 1 can be expanded

to introduce related levels for evaluation of performance. Some

important PQ levels that are described in the standards include

the following.

1) Compatibility levels. These define the basic expectation

for performance of the supply system. Therefore, they can

provide the basis for manufacturers to design equipment

for immunity to supply system PQ variations. Require-

ments for regulation of the steady-state voltage have been

in place for power systems around the world for many

years. New standards, such as the EuroNorm EN 50160,

Physical characteristics of electricity supplied by publicdistribution systems define the requirements in other PQ


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Fig. 2. Illustration of a measured trend for a PQ characteristic compared todifferent levels defined for assessing performance.

categories (harmonics, voltage fluctuations, unbalance,

interruptions, voltage dips). The requirements for system

performance in these different categories are known as

voltage characteristics.

2) Planning limits. Planning limits are established by utili-

ties for comparison with actual PQ levels. Measured PQ

levels that exceed the planning levels are an indication

of a possible problem on the system that should be ad-

dressed. There should be some margin between planning

levels and required voltage characteristics.

3) Equipment Immunity Characteristics. The equipment

immunity levels should be coordinated with the voltage

characteristics to make sure that the equipment can op-

erate under the full range of possible PQ levels. There

should be some margin between the equipment immunity

levels and the voltage characteristics.

Fig. 2 shows these levels with a trend of measured data

for an actual PQ characteristic. Note that this could be any ofthe steady-state PQ quantitiesvoltage deviations, unbalance,

harmonics, flicker. It is worthwhile to consider the status of

standards and needs for standards development briefly in each

of these categories.

A. Voltage Regulation

There is no such thing as steady state on the power system.

Loads are continually changing and the power system is con-

tinually adjusting to these changes. All of these changes and

adjustments result in voltage variations that are referred to as

long duration voltage variations. These can be undervoltagesor overvoltages, depending on the specific circuit conditions.

Characteristics of the steady-state voltage are best expressed

with long duration profiles and statistics. Important characteris-

tics include the voltage magnitude and unbalance. According to

the latest draft of IEEE Standard P1159, IEEE Recommended

Practice for Monitoring Power Quality, long duration varia-

tions are considered to be present when the limits are exceeded

for greater than 1 min.

Most end-use equipment is not very sensitive to these volt-

age variations, as long as they are within reasonable limits.

ANSI C84.1-1995 [11] specifies steady-state voltage tolerances

expected on a power system. It recommends that equipment

be designed to operate with acceptable performance underextreme steady-state conditions of+6% and 13% of nominal

120/240-V system voltage. Protective devices may operate to

remove the equipment from service outside of this range.

European limits are specified in EN 50160 [4]. Limits for

supply voltage magnitude variations are specified for low-

voltage (LV) systems. The supply voltage rms magnitude,

whether line-to-neutral, or line-to-line, should be within 10%

for 95% of a week. Voltage magnitudes are characterized by ameasurement period of 10 min. The evaluation procedure is that

95% of the 10-min values for one week should be within the

specified limits. These limits are based on the compatibility lev-

els specified in IEC 61000-2-2 [1], 61000-2-4 [2], and 61000-

2-8 [3] and also discussed further in [5]. In general, all 10-min

mean rms values of supply voltage are expected to be within

+10%/15%, excluding dips, interruptions and overvoltages.

B. Voltage Unbalance

The most recent version of ANSI C84.1 [11] includes rec-

ommended limits for voltage unbalance on the power system. In

the ANSI Standard, unbalance is a steady-state quantity defined

as the maximum deviation from the average of the three phase

voltages or currents, divided by the average of the three phase

voltages or currents, expressed in percent. In the international

standards, unbalance is more commonly defined as the ratio

of the negative sequence component to the positive sequence

component.

The primary source of voltage unbalance less than 2% is

unbalanced single-phase loads on a three-phase circuit. Voltage

unbalance can also be the result of capacitor bank anomalies,

such as a blown fuse on one phase of a three-phase bank. Severe

voltage unbalance (greater than 5%) can result from single-

phasing conditions.Voltage unbalance is most important for three phase motor

loads. ANSI C84.1 recommends that the maximum voltage un-

balance measured at the meter under no load conditions should

be 3%. Unbalance greater than this can result in significant

motor heating and failure if there are not unbalance protection

circuits to protect the motor.

The EN 50160 limit for unbalance is 2% for normal systems,

based on the compatibility levels specified in IEC 61000-2-2.

A limit of 3% applies on systems with single-phase loads.

For evaluation, unbalance levels are characterized in 10-min

periods. For compliance, 95% of these 10-min values should

be within the limits in a one-week measurement period.

C. Harmonics

Harmonic voltage distortion results from the interaction of

harmonic currents (created by nonlinear loads and other nonlin-

ear devices on the power system) with the system impedance.

The harmonic standard, IEEE Standard 519-1992, IEEE Rec-

ommended Practices and Requirements for Harmonic Control

in Electrical Power Systems [7], has proposed two way respon-

sibility for controlling harmonic levels on the power system.

End users must limit the harmonic currents injected onto the

power system. The power supplier will control the harmonic

voltage distortion by making sure system resonant conditionsdo not cause excessive magnification of the harmonic levels.


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TABLE IHARMONIC VOLTAGE DISTORTION LIMITS FROM IEEE STANDARD 519-1992

TABLE IIHARMONIC CURRENT LIMITS FOR INDIVIDUAL END USERS FROM IEEE STANDARD 519-1992

(EXPRESSED IN PERCENT OF THE RATED LOAD CURRENT IL)

Harmonic distortion levels can be characterized by the com-

plete harmonic spectrum with magnitudes and phase angles

of each individual harmonic component. It is also common

to use a single quantity, the total harmonic distortion (THD),

as a measure of the magnitude of harmonic distortion. Forcurrents, the distortion values must be referred to a constant

base (e.g., the rated load current or demand current) rather than

the fundamental component. This provides a constant reference

while the fundamental can vary over a wide range.

Harmonic evaluations often involve a combination of mea-

surements and analysis (possibly simulations). It is important to

understand that harmonics are a continuous phenomena, rather

than a disturbance (like a transient). Because harmonics are

continuous, they are best characterized by measurements over

time so that the time variations and the statistical character-

istics can be determined. These characteristics describing the

harmonic variations over time should be determined along withsnapshots of the actual waveforms and harmonic spectrums at

particular operating points.

Harmonic evaluations on the utility system involve proce-

dures to make sure that the quality of the voltage supplied to

all customers is acceptable. IEEE Standard 519-1992 provides

guidelines for acceptable levels of voltage distortion on the

utility system (Table I). Note that recommended limits are

provided for the maximum individual harmonic component and

for the THD.

These voltage distortion limits apply at the point of common

coupling (PCC), which will be on the medium voltage system

for most industrial and commercial customers. The concept of

the PCC and many other questions related to the application ofharmonic limits are addressed in an application guide for ap-

plying harmonic limits that is currently being finalizedIEEE

Standard 519.1 [18]. Note that higher voltage distortion levels

may be appropriate within the end-user facility and this is being

addressed in the revision effort for IEEE Standard 519. Most

end-use equipment is not affected by voltage distortion levelsbelow 8%. In fact, the compatibility level for voltage distortion

on LV and MV systems specified in IEC 61000-2-2 is 8% (this

is the voltage distortion level that should be exceeded less than

5% of the time).

Most harmonic problems occur at the end-user level, rather

than on the utility supply system. Most nonlinear devices

are located within end-user facilities and the highest voltage

distortion levels occur close to the sources of harmonics. The

most significant problems occur when an end user has nonlinear

loads and also has power factor correction capacitors that result

in resonance conditions.

In order to maintain acceptable levels of voltage distortion,harmonic current limits at the PCC are described in IEEE

Standard 519 as well. These are summarized in Table II.

There are a number of important concepts introduced in these

current limits. For instance, the harmonic limits are dependent

on the strength of the system where the customer is connected

(ratio of IL to the short circuit current, ISC). Also, a new

quantity called the total demand distortion (TDD) is introduced

as follows:

TDD =

n=2

I2n

IL 100%


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where

In magnitude of individual harmonic components (rms

amps);

n harmonic order;

IL maximum demand load current (rms amps).

International compatibility levels for harmonics are specified

in IEC 61000-2-2. These are used to develop utility limits in

EN 50160, in IEC Standard 61000-3-6 [6], and in G5/4 [8]. EN

50160 specifies limits for individual harmonic components up

to the 25th and for the THD. The limits are not as strict as the

recommended limits in IEEE Standard 519 and some efforts

to coordinate these limits are under way in the next revision

to IEEE Standard 519. For instance, the limit for THD is

8%. These limits are evaluated using a measurement procedure

defined in IEC 61000-4-7 [19]. This involves calculating har-

monic values in 3-s periods and then combining these 3-s values

to obtain 10-min values. The limits should be met by 95% of the

10-min values during an assessment period of one week. One of

the most important standards coordination efforts needed in theharmonics area is to achieve more of a consensus on methods

and indexes for measuring and characterizing harmonic levels

using statistical procedures.

D. Flicker

Voltage fluctuations are systematic variations of the voltage

or a series of random voltage changes, the magnitude of which

does not normally exceed the voltage ranges specified by ANSI

C84.1. These fluctuations are often referred to as flicker. They

are characterized by the magnitude of the voltage changes

and the frequency with which they occur. A plot of the rmsvoltage magnitude versus time can be used to illustrate the

variations.

The most important impact of these fluctuations is that they

cause variations in the light output of various lighting sources.

Sensitivity curves have been developed for incandescent light-

ing that show how the voltage fluctuations can cause unac-

ceptable variations in the light output. These sensitivity curves

were used to specify a measurement device that can character-

ize the potential for voltage variations to cause unacceptable

light flicker. This measurement device (the flickermeter) has

been standardized in IEC 61000-4-15 [20] and is now the

international standard for measuring voltage fluctuations andflicker.

The original flickermeter specification was based on the

effects of voltage fluctuations on a 60-W incandescent light

on 230-V systems. A 60-W incandescent light bulb designed

for 120 V is not as sensitive to the same voltage fluctuations

because the filament is larger (longer time constant) to handle

the higher current levels associated with the same watt rating.

As a result, an additional weighting curve was developed for

120-V applications, which are more common in North America.

The 120- and 230-V weighting curves are compared in Fig. 3.

In North America, the flicker measuring procedure should use

the method standardized in IEC 61000-4-15 [20] with the

120-V weighting curve employed. This has now been formal-ized in an IEEE standardIEEE Standard 1453 [10].

Fig. 3. Comparison of 120- and 230-V weighting curves for flickermetercalculations.

Output from the flickermeter consists of two basicquantities.

1) The short-term flicker severity Pst. A Pst value is ob-

tained every 10 min. There are 144 Pst samples each day.

Pst is a per-unitized quantity where 1 per unit represents

a flicker severity that should correspond approximately to

objectionable flicker in 40-W incandescent lights.

2) The long-term flicker severity Plt. Each Plt value is cal-

culated from 12 successive Pst values using the following

formula:

Plt =3 112

12j=1

P3stj .

Each of these two basic quantities can be characterized in

terms of their statistics. The following statistical quantities are

recommended in a recent report prepared by the Conference

Internationale des Grands Reseaux Electriques C4.07 Task

Force [23]. They should be calculated after measuring over a

period of time, recommended to be at least one week.

1) Pst95% is the Pst level that is exceeded 5% of the time.

This value is compared with planning levels for the

system being evaluated.

2) Pst99% is the Pst level that is exceeded 1% of the time.This would be compared with planning levels with some

margin (e.g., planning levels times 1.01.5).

3) Plt95% is the Plt level that is exceeded 5% of the time.

This is the value that is compared to voltage characteris-

tics (limits).

IEC developed standard 61000-3-7, Assessment of Emission

Limits for Fluctuating Loads in MV and HV Power Systems [9]

to provide a procedure for assessing flicker levels and applying

limits at individual end users connected to the high-voltage

(HV) system. This standard was developed in close cooperation

with both the United States and Canada and includes the

120-V weighting curve described above for the North Americasystems.


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Fig. 4. Example of a voltage sag characterized by an rms voltage plot (and anactual waveform plot).

V. STANDARDS FO R PQ DISTURBANCES AND RELIABILITY

Disturbances are events that do not occur on a regular ba-

sis but can impact the performance of equipment [15]. They

include transients, voltage variations (sags swells), and inter-

ruptions. Interruptions that last more than 1 min (sometimes

5 min) are usually referred to as outages and are included

in reliability statistics. Short interruptions are classified with

PQ variations.

A. Voltage Sags and Interruptions

Voltage sags fall in the category of short duration voltage

variations. According to IEEE Standard 1159 and IEC defi-

nitions [13] and [14], these include variations in the funda-mental frequency voltage that last less than 1 min. These

variations are best characterized by plots of the rms voltage

versus time (Fig. 4) but it is often sufficient to describe them by

a voltage magnitude and a duration that the voltage is outside of

specified thresholds. It is usually not necessary to have detailed

waveform plots since the rms voltage magnitude is of primary

interest.

The voltage variations can be a momentary LV (voltage sag),

HV (voltage swell), or loss of voltage (interruption). IEEE Stan-

dard 1159 specifies durations for instantaneous, momentary,

and temporary disturbances.

Voltage sags are typically caused by a fault somewhere onthe power system. The voltage sag occurs over a significant

area while the fault is actually on the system. As soon as a

fault is cleared by a protective device, voltage returns to normal

on most parts of the system, except the specific line or section

that is actually faulted. The typical duration for a transmission

system fault is about six cycles. Distribution system faults can

have significantly longer durations, depending on the protection

philosophy. The voltage magnitude during the fault will depend

on the distance from the fault, the type of fault, and the system

characteristics.

End users can evaluate the economics of power conditioning

equipment if they have information describing the expected

system voltage sag performance. A complete methodology forthis evaluation is provided in IEEE Standard 1346 [21]. The

expected voltage sag performance from the supply system is

used in combination with equipment sensitivity characteristics

to estimate the number of times per year that a process will

be disrupted. Fig. 5 illustrates the contour plot method of

characterizing system performance for these evaluations.

There is considerable standards work under way to define

indexes for characterizing voltage sag performance. In IEEE,this paper is being coordinated by IEEE P1564 [16]. The

most common index use is the system average rms (variation)

frequency index (SARFI). This index represents the average

number of voltage sags experienced by a end user each year

with a specified characteristic. For SARFIx, the index would

include all of the voltage dips where the minimum voltage

was less than x. For example, SARFI70 represents the expected

number of voltage sags where the minimum voltage is less than

70%. The SARFI index and other alternatives for describing

voltage sag performance are being formalized in the IEEE

Standard 1564 Working Group. Fig. 6 is an example of SARFI

levels calculated from a survey of performance for distribution

systems in the United States.

B. Transients

The term transients is normally used to refer to fast changesin the system voltage or current. Transients are also in the

category of disturbances, rather than steady-state variations.

Transients can be measured by triggering on the abnormality

involved. For transients, this could be the peak magnitude, the

rate of rise, or just the change in the waveform from one cycle

to the next. Transients can be divided into two subcategories,

impulsive transients and oscillatory transients, depending on

the characteristics.Transients are normally characterized by the actual wave-

form, although summary descriptors can also be developed

(peak magnitude, primary frequency, rate-of-rise, etc.). Fig. 7

gives a capacitor switching transient waveform. This is one of

the most important transients that is initiated on the utility sup-

ply system and can affect the operation of end-user equipment.Other important causes of transient voltages include lightning

surges and switching operations within a facility.

Transient problems are solved by controlling the transient at

the source, changing the characteristics of the system affect-

ing the transient or by protecting equipment so that it is not

impacted. For instance, capacitor switching transients can becontrolled at the source by closing the breaker contacts close

to a voltage zero crossing. Magnification of the transient canbe avoided by not using LV capacitors within the end-user

facilities. The actual equipment can be protected with filters or

surge arresters.

The most well-known standard in the field of transient over-

voltage protection is ANSI/IEEE C62.41-1991, IEEE Guide for

Surge Voltages in Low Voltage AC Power Circuits [12]. This

standard defines the transient environment that equipment maysee and provides specific test waveforms that can be used for

equipment withstand testing. The transient environment is a

function of the equipment or surge suppressor location within

a facility as well as the expected transients from the supplysystem.


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Fig. 5. Contour plot method of characterizing system voltage sag performance (IEEE Standard 1346).

Fig. 6. Example of voltage sag performance levels (SARFI) for distribu-tion systems in the United States from the EPRI Distribution Power Qualityproject [22].

Fig. 7. Capacitor switching transient.

VI. FUTURE DIRECTION FOR PQ STANDARDS

Benchmarking efforts from around the world have provided

the initial basis for defining expected PQ performance of supplysystems. These performance standards should include at least:

1) interruptions (including momentary);

2) voltage sags;3) steady-state voltage regulation;

Fig. 8. Flow of PQ standards development activities.

4) voltage unbalance (negative sequence);

5) harmonic distortion in the voltage;6) transient voltages.

There is a need for significant additional research to establish

the relationship between PQ/reliability levels and the various

characteristics of the supply system. Also, the PQ/reliability

characteristics need to be defined in a more statistical mannerto allow more effective risk assessments by end users using

statistical techniques.

In turn, equipment manufacturers must be able to provide in-formation describing the sensitivity of their equipment to these

variations. With information on typical system performance

based on historical and calculated data along with information

on equipment sensitivity, end users will be able to perform eco-

nomic evaluations of power conditioning alternatives. Standard

procedures for the economic analysis will incorporate statistical

risk assessment methods in the future.

Ongoing monitoring efforts and case studies will provide

the information to characterize system performance and to

understand the susceptibility of different types of end-user

systems. Monitoring of PQ should become a more standard

part of the overall system monitoring (both at the utility level

and the customer level). These monitoring efforts should becoordinated between the utility and the customer with emphasis


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TABLE III

on remote monitoring and data collection systems with more

automated data analysis capabilities. IEC 61000-4-30 [17] pro-

vides a good start for standardizing PQ measurements but there

is a need for additional standards development for monitoring

to characterize PQ for advanced applications.

Analytical tools will also benefit from the increased level of

monitoring and characterization. Models should be improved

and the tools themselves should become easier to use. There is

considerable opportunity to facilitate analysis of PQ issues with

standard models and modeling techniques.

The overall focus needs to be on economics using a systemsapproach. We need to develop tools that can help find the opti-

mum system design including power conditioning for sensitive

equipment. The alternatives should include improved immunity

at the equipment level, power conditioning at the equipment

level, power conditioning at more centralized locations within

the end-user system, and measures to improve performance on

the utility system.

Fig. 8 illustrates the overall flow of standards develop-

ment activities in the area of PQ and reliability. Under-

standing of system characteristics and end-use equipment

characteristics leads to tools and methods to assess perfor-

mance and improve the overall performance in an optimummanner.


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VII. CONCLUSION

There has been significant progress in the development of

PQ standards. Recent efforts have been focused on harmo-

nizing standards between IEEE and IEC and this is an ongo-

ing process. Continued efforts to understand system PQ as a

function of system characteristics and to coordinate the system

characteristics with the performance of end-use equipment areunder way. Both system performance and end-use equipment

characteristics are being described with more standardized

methods. This information will lead to improve economics of

PQ management in the future.

APPENDIXIEEE PQ STANDARDS

See Table III.

ACKNOWLEDGMENT

The authors would like to thank the contribution and par-

ticipation of the members of the SCC22 in developing the

information for this paper.

REFERENCES

[1] Electromagnetic Compatibility (EMC)Part 2-2: EnvironmentCompatibility Levels for Low-Frequency Conducted Disturbancesand Signaling in Public Low-Voltage Power Supply Systems,IEC 61000-2-2, ed. 2, 2002.

[2] Electromagnetic Compatibility (EMC)Part 2-4: EnvironmentCompatibility Levels in Industrial Plants for Low-Frequency Conducted

Disturbances, IEC 61000-2-4, ed. 2, 2002.

[3] Electromagnetic Compatibility (EMC)Part 2-12: EnvironmentCompatibility Levels for Low-Frequency Conducted Disturbancesand Signaling in Public Medium-Voltage Power Supply Systems,IEC 61000-2-12, ed. 1, 2003.

[4] Voltage Characteristics of Electricity Supplied by Public DistributionSystems, EN 50160:11 1999.

[5] Electricity SupplyQuality of Supply, Part 2Voltage Characteristics,Compatibility Levels, Limits and Assessment Methods, NRS 048-2:2002,Nov. 5, 2002. 2nd ed., draft 4.

[6] Electromagnetic Compatibility (EMC)Part 3: Limits, Section 6:Assessment of Emission Limits for Harmonics in MV and HV Power

Systems, IEC 61000-3-6, 1996.[7] IEEE Recommended Practices and Requirements for Harmonic Control

in Electrical Power Systems, IEEE Standard 519-1992.[8] Planning Levels for Harmonic Voltage Distortion and the Connection

of Nonlinear Equipment to Transmission Systems and DistributionNetworks in the United Kingdom, Engineering Recommendation G5/4,

2001.[9] Electromagnetic Compatibility (EMC)Part 3: Limits, Section 7: Assess-

ment of Emission Limits for Fluctuating Loads in MV and HV PowerSystems, IEC 61000-3-7, 1996

[10] IEEE Guide for Measurement and Limits of Voltage Flicker on AC PowerSystems, IEEE Standard P1453, draft 4, Jul. 2002.

[11] Electrical Power Systems and EquipmentVoltage Ratings (60 Hz),ANSI C84.1-1995 (R2001).

[12] IEEE Recommended Practices for Surge7 Voltages in Low-VoltageAC Power Circuits, IEEE/ANSI C62.41-1991.

[13] Electromagnetic Compatibility (EMC)Part 2-8: EnvironmentVoltageDips and Short Interruptions on Public Electric Power Supply SystemsWith Statistical Measurement Results, IEC 61000-2-8, 2002.

[14] Electromagnetic Compatibility (EMC) Part 4: Testing and MeasuringTechniquesSection 11: Voltage Dips, Short Interruptions, and VoltageVariations Immunity Tests, IEC 61000-4-11, 2004.

[15] Specification for Semiconductor Processing Equipment Voltage SagImmunity, SEMI F47-0200, 1999.[16] Voltage Sag Indices, IEEE Standard 1564 (Draft 4), 2003.

[17] Electromagnetic Compatibility (EMC) Part 4-30: Testing and MeasuringTechniquesPower Quality Measurement Methods, IEC 61000-4-30,Jan. 1997.

[18] Application Guide for Applying Harmonic Limits on Power Systems,(Final Draft for Balloting), IEEE Standard 519.1, 2004.

[19] Electromagnetic Compatibility (EMC) Part 47: Testing and Measure-ment TechniquesGeneral Guide on Harmonics and Interharmonics

Measurements and Instrumentation, for Power Supply Systems and Equip-

ment Connected Thereto, IEC 61000-4-7, 2002.[20] Electromagnetic Compatibility (EMC)Part 4: Testing and Measure-ment TechniquesSection 15: FlickermeterFunctional and Design, IEC61000-4-15, 2003.

[21] IEEE Recommended Practice for Evaluating Electric Power System Com-patibility With Electronic Process Equipment, IEEE Standard 1346-1998(R2004), 2004.

[22] An assessment of distribution system power quality, EPRI, Palo Alto,CA, Rep. EPRI TR-106294, 1996.

[23] Power quality indices and objectives, CIGRE WG C4.07 Rep. CIGRETechnical Brochure 261, Oct. 2004.

David B. Vannoy (S65M67), deceased, received the B.E.E. and M.E.E. de-grees from the University of Delaware, Newark, in 1966 and 1967, respectively.

He worked for over 31 years with Delmarva Power in the Engineering andOperating Departments. He was an Independent Consultant at the time thispaper was developed. He managed Delmarva Powers Power Quality Group,which he developed beginning in 1987. He was Chairman of the IEEE PowerQuality Standards Coordinating Committee (SCC22).

Mr. Vannoy was active on numerous IEEE power-quality (PQ) standardscommittees and was founding President of the Delaware Valley Power QualityGroup, a nonprofit educational forum on PQ. He was a Registered ProfessionalEngineer in the State of Delaware.

Mark F. McGranaghan (S77M78SM04) is an Associate Vice Presidentof EPRI Solutions, Knoxville, TN. He coordinates a wide range of servicesoffered to electric utilities and critical industrial facilities throughout the world.These services include research projects, seminars, monitoring services, powersystems analysis projects, performance benchmarking, testing services, failureanalysis, and designing solutions for system performance improvement. Histechnical background is in the area of power system modeling and analysis.He is an expert in the areas of harmonic analysis, transient analysis, reliability,PQ improvement, and power systems monitoring applications. He has writtennumerous papers, is active in both IEEE and International ElectrotechnicalCommission standards development, and has taught power system workshopsand seminars throughout the world.

S. Mark Halpin (S89M93SM02F05) received the B.E.E., M.S., andPh.D. degrees from Auburn University, Auburn, AL, in 1988, 1989, and 1993,respectively.

He is currently a Professor with the Department of Electrical and ComputerEngineering, Auburn University. His teaching interests include power systems,control systems, and network analysis. His research interests are in the areasof modeling and simulation techniques for large-scale power systems, powersystem transients, and computer algorithms.

Dr. Halpin is active in the IEEE Power Engineering Society where he serves

as the Chair of the Task Force to revise IEEE Std. 519 and in the IEEE IndustryApplications Society where he serves as Chairman of the Working Group onHarmonics.


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W. A. Moncrief(M74SM82) received the B.E.E. and M.S.E.E. degrees fromthe Georgia Institute of Technology (Georgia Tech), Atlanta, in 1969 and 1972,respectively.

He was with Georgia Power in System Protection, where he headed theEnhanced Power Quality Department, and then moved to the Research Center(now NEETRAC). He was a Project Manager for the Electric Power Re-search Institute, Palo Alto, CA, and is currently a Professional Engineer withHood-Patterson & Dewar, Norcross, GA. He is also on the staff of the Georgia

Tech Music Department.Mr. Moncrief is the Chair of the IEEE Power Engineering Society (PES)Harmonics Working Group and Vice-Chair (PES) of IEEE SCC-22. He alsoparticipates on a number of other IEEE standards committees. He also serves onthe Technical Advisory Group to IEC SC77A, Electromagnetic Compatibility.

D. Daniel Sabin (S92M93SM01) received the B.S. degree in electricalengineering from Worcester Polytechnic Institute, Worcester, MA, and the M.E.degree in electric power engineering from Rensselaer Polytechnic Institute,Troy, NY.

He is with EPRI Solutions, Inc., Beverly, MA, as a Manager of MonitoringSystems. His primary responsibilities involve developing PQ database software,managing, and completing PQ research projects, and providing consultation toelectric utilities on PQ monitoring efforts.

Mr. Sabin is the Chair of SCC22, Secretary of the IEEE Power QualitySubcommittee, Chair of the IEEE P1564 Voltage Sag Indices Task Force, anda Member of the Editorial Board for the IEEE TRANSACTIONS ON POWERDELIVERY. He is also a Registered Professional Engineer in the State ofTennessee.

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