handbook for electricity metering

HANDBOOKFOR

ELECTRICITYMETERING

10TH EDITION

HANDBOOK FOR ELECTRICITY METERING 10TH EDITION

Edison Electric Institute (EEI) is the association of United States shareholder-owned electric companies, international affiliates and industry associates worldwide. In 2000, our U.S. members served morethan 90 percent of the ultimate customers in the shareholder-owned segment of the industry, and nearly 70 percent of all electric utility ultimate customers in the nation. They generated almost 70 percent of the electricity generated by U.S. electric utilities.

Organized in 1933, EEI works closely with its members, representingtheir interests and advocating equitable policies in legislative and regula-tory arenas. In its leadership role, the Institute provides authoritativeanalysis and critical industry data to its members, Congress, governmentagencies, the financial community and other influential audiences. EEI provides forums for member company representatives to discussissues and strategies to advance the industry and to ensure a competitiveposition in a changing marketplace.

EEIs mission is to ensure members success in a new competitive environment by:

Advocating Public Policy

Expanding Market Opportunities

Providing Strategic Business Information

For more information on EEI programs and activities, products and services, or membership, visit our web site at www.eei.org.

ii HANDBOOK FOR ELECTRICITY METERING

COPYRIGHT 2002 BY EDISON ELECTRIC INSTITUTE701 Pennsylvania Avenue, N.W.Washington, D.C. 20004-2696

First, Second, and Third editions entitledElectrical Metermans Handbook

copyright 1912, 1915, 1917by the National Electric Light Association

Fourth edition entitledHandbook for Electrical Metermen

copyright 1924by the National Electric Light AssociationFifth, Sixth, and Seventh editions entitled

Electrical Metermens Handbookcopyright 1940, 1950, and 1965by the Edison Electric Institute

Eighth, Ninth, and Tenth editions entitledHandbook for Electricity Metering

Copyright 1981, 1992, and 2002by the Edison Electric Institute

First edition, 1912 . . . . . . . . . . . . . . . .5,000 copiesSecond edition, 1915 . . . . . . . . . . . . .2,500 copiesThird edition, 1917 . . . . . . . . . . . . . . .5,000 copiesFourth edition, 1923 . . . . . . . . . . . . .21,300 copiesFifth edition, 1940 . . . . . . . . . . . . . . .15,000 copiesSixth edition, 1950 . . . . . . . . . . . . . . .25,000 copiesSeventh edition, 1965 . . . . . . . . . . . .20,000 copiesEighth edition, 1981 . . . . . . . . . . . . .17,000 copiesNinth edition, 1992 . . . . . . . . . . . . . .10,000 copiesTenth edition, 2002 . . . . . . . . . . . . . .10,000 copies

EEI Publication No. 93-02-03

Handbook for Electricity Metering.Tenth Editionp. cm.

Includes index.ISBN 0-931032-52-0

1. Electric meters. I. Edison Electric InstituteTK301.H428 2002621.3745dc20

iii

PREFACETO THE TENTH EDITION

The first edition of the Electrical Metermans Handbook, now the Handbook forElectricity Metering, was first published in 1912. Nine revisions have since beenpublished; the ninth edition appeared in 1992. As in the previous editions, theemphasis has been on fulfilling the needs of the metering practitioner.

In the tenth edition each chapter includes updated text and new graphics. The following major updates have been made to the 10th edition: new exampleson complex numbers; addition of current measurement technology from basic to advance meters; expansion of information on optical voltage and current sensors; inclusion of new meter diagrams; current metering testing practices;updates on standard metering laboratory and related standards; and new elec-tronic data collection information. To make the Handbook convenient either as areference or textbook, a great deal of duplications has been permitted.

In the preparations of this Handbook, the Advisory Teams wish to make grate-ful acknowledgment for all the help received. Above all, credit must be given to the editors and committees responsible for previous editions of the Handbook.Although the tenth edition has been rewritten and rearranged, the ninth editionprovided most of the material that made this rewriting possible.

The contribution made by the manufacturers has been outstanding for thechapters concerning their products and they have freely provided illustrations,assisted in editing chapters and provided text.

It is hoped that future editions will be prepared as new developments makethem necessary. If users of this Handbook have any suggestions which they believe would make future editions more useful, such suggestions, comments, or criticisms are welcomed. They should be sent to the Edison Electric Institute,701 Pennsylvania Avenue, N.W., Washington, D.C. 20004-2696.

vSTAFFHarley Gilleland, The HarGil Group . . . . . . . . . . . . . . . . . . . . . . . . .Project ManagerRandall Graham . . . . . . . . . . . . . . . . . . . . . . . . .Production Services RepresentativeKenneth Hall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Manager, Distribution IssuesNiki Nelson . . . . . . . . . . . . . .Manager, Communication and Product Development

EDITORIAL COMMITTEEJim Andrews . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .American Electric Power Jim Arneal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Alliant EnergyRuss Borchardt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Xcel Energy Jim Darnell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Reliant Energy, HL&PJim DeMars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Florida Power & LightJohn Grubbs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Alabama Power CompanyKevin Heimiller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Western ResourcesSid Higa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Hawaiian ElectricAlan Ladd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Central Main Power CompanyTim Morgan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Duke EnergyYoung Nguyen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Pacific Gas & ElectricTony Osmanski . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .PPL UtilitiesLauren Pananen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .PacifiCorpRandy Pisetzky . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .TECO EnergyEllery Queen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Georgia PowerDave Scott . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Northeast UtilitiesStephen Shull . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Empire District Electric CompanyJim Thurber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Baltimore Gas & Electric CompanyChris Yakymyshyn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Montana State University

CONTRIBUTORSTed Allestad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Seattle City Light Ron Boger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Portland General Electric Theresa Burch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Puget Sound Energy Mike Coit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .GE Debra Lynn Crisp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Florida Power & LightWes Damien . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Allegheny PowerDoug Dayton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ITECAl Dudash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ABB Greg Dykstal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .SiemensTim Everidge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Radian ResearchJim Fisher . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .SchlumbergerJohn Gottshalk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Benton PUD Roy Graves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ComEdRick Hackett . . . . . . . . . . . . . . . . . . . . .Central Vermont Public Service CorporationDavid Hart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ABB Mark Heintzelman . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Idaho Power CompanyMatt Hoffman . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .NIPSCOScott Holdsclaw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ABB James Hrabliuk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .NxtPhase

vi HANDBOOK FOR ELECTRICITY METERING

Al Jirges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Montana-Dakota UtilitiesJohn Junker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .SiemensBob Kane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .PEPCOJerry Kaufman . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Illinois Power CompanyKelley Knoerr . . . . . . . . . . . . . . . . . . . . . . . . . . . .Wisconsin Electric Power CompanyJim Komisarek . . . . . . . . . . . . . . . . . . . . . . . . .Wisconsin Public Service CorporationSteve Magnuson . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .PacifiCorp Steve Malich . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Tampa Electric CompanyBob Mason . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ABBGlenn Mayfield . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Radian ResearchDick McCarthy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Avista CorporationJohn McClaine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Puget Sound Energy Paul Mobus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ABBJohn Montefusco . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Progress EnergyMark L. Munday . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ABBKraig J. Olejniczak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .University of ArkansasJerry Peplinski . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Madison Gas & Electric CompanyBruce Randall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .SiemensChris Reinbold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ABBBud Russell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Themeterguy.com John Schroeder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Alliant EnergyDale Sindelar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Snohomish County PUD Victor Sitton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ABBChris Smigielski . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Consumers EnergyClark Smith . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .PacifiCorp-retired Kathy Smith . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ABB Tommy Smith . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Georgia PowerDavid Stickland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .PacifiCorp Leslie Thrasher . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .SchlumbergerDave Troike . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Illinois Power CompanyJohn Voisine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .SiemensDelbert Weers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ITECScott Weikel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ABBChuck Weimer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .WECODamien Wess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Allegheny PowerJames B. West . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Ameren Service Corporation

CONTRIBUTING ORGANIZATIONSAEIC Meter & Service Committee

EEI Distribution & Metering CommitteeGreat Northwest Meter Group

vii

C H A P T E R 1

INTRODUCTION TO THE METER DEPARTMENTThe Electric Utility and the Community . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1The Duties of the Meter Department . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Customer Contacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2Knowledge Required in Metering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3Meter Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

C H A P T E R 2

COMMON TERMS USED IN METERINGAlphabetical List of Technical Terms, with Explanations . . . . . . . . . . . . . . . . . . . . .7

C H A P T E R 3

MATHEMATICS FOR METERING (A BRIEF REVIEW)Basic Laws of Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25The Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27The Right Triangle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28Trigonometric Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29Scientific Notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33Complex Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34Complex Numbers in Rectangular Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34Addition and Subtraction of Complex Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . .35Multiplication of Complex Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35Division, Conjugation, and Absolute Value of Complex Numbers . . . . . . . . . . . .35Complex Numbers Written in Polar Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36Multiplication of Complex Numbers in Polar Form . . . . . . . . . . . . . . . . . . . . . . . . .38Division of Complex Numbers in Polar Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39Basic Computations Used in Metering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

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C H A P T E R 4

ELECTRICAL CIRCUITSDirect CurrentIntroduction to Direct-Current Electric Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . .45Physical Basis for Circuit Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45Resistance and Ohms Law as Applied to DC Circuits . . . . . . . . . . . . . . . . . . . . . . .46Kirchhoffs Current Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47Kirchhoffs Voltage Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48Resistances Connected in Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51Resistances Connected in Parallel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53Resistances in Series-Parallel Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54Power and Energy in DC Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56Three-Wire Edison Distribution System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56Summary of DC Circuit Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57

Alternating-Current Single-Phase CircuitsIntroduction to Alternating-Current Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58Sinusoidal Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58Fundamental Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59Phasors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60Inductance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63Capacitance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65Resistance and Ohms Law as Applied to AC Circuits . . . . . . . . . . . . . . . . . . . . . . .67Impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68Power and Energy in Single-Phase AC Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72Transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75Harmonic Frequencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77

Alternating-Current Three-Phase CircuitsBalanced Three-Phase Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78Balanced Three-Phase Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78Balanced Three-Phase Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .81Balanced Three-Phase Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .81Per-Phase Equivalent Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83Power and Energy in Three-Phase AC Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83Power Triangle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83

Distribution CircuitsWye Wye Transformer Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85Wye Delta Transformer Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86Delta Wye Transformer Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86Delta Delta Transformer Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87

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C H A P T E R 5

SOLID-STATE ELECTRONICS

The Atom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89

Semiconductor Electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91Hole Current and Electron Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91N and P Type Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92P-N Junction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93Semiconductor Diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93Transistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95

Digital Electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96Number Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96Microprocessors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102

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INSTRUMENTSElectronic Digital Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103Permanent-Magnet, Moving-Coil Instrument . . . . . . . . . . . . . . . . . . . . . . . . . . . .107Thermocouple Instrument . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .109The Moving-Iron Instrument . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110Electrodynamometer Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .112Thermal Ampere Demand Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116Instrument Scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .117Measurement of Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .118Selection of Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .121Care of Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .122Influence of Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123Influence of Stray Fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123Mechanical Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123Influence of Instruments on Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124Accuracy Rating of Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124Maintenance of Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125

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THE WATTHOUR METER

The Generic Watthour Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127

Multi-Element (Multi-Stator) Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .129The Evolution of the Polyphase Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .129Three-Wire Network Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .132Three-Wire, Three-Phase Delta Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134Four-Wire, Three-Phase Wye Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .138

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Two-Element (Two-Stator), Three-Current Sensor Meter . . . . . . . . . . . . . . . . . . .139Four-Wire, Three-Phase Delta Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .145Two-Element (Two-Stator), Three-Current Sensor Meter . . . . . . . . . . . . . . . . . . .146Multi-Element (Multi-Stator) Meter Applications with Voltage

Instrument Transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .148

Electromechanical Metering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .151The Motor in an Electromechanical Single-Stator AC Meter . . . . . . . . . . . . . . . .151The Permanent Magnet or Magnetic Brake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157Compensations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .161Anti-Creep Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166Frequency Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .167Waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .167Meter Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .168Meter Rotor Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .168Mechanical Construction of the Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .170Polyphase Electromechanical Meter Characteristics and Compensations . . . .172Driving and Damping Torques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .172Individual Stator Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .173Current Damping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .173Imbalanced Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .173Interference between Stators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .174Interference Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175Design Considerations to Reduce Interference . . . . . . . . . . . . . . . . . . . . . . . . . . .175Multi-Stator Meter Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .176Special Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .178

Solid-State Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .178Evolution of Solid-State Metering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .178Current Sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .181Voltage Sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183Multiplication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183

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DEMAND METERSExplanation of Term Demand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .191Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .191Why Demand is Metered . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192Maximum Average Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .194Maximum Average Kilovoltamperes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .194General Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195Instantaneous Demand Recorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195Offsite Demand Recorder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196Pulse-Operated Demand Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197Electronic Demand Meters with Time of Use and Recorder . . . . . . . . . . . . . . . . .197

CONTENTS xi

Watthour Demand Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197KiloVAR or Kilovoltampere Demand Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .202Pulse-Operated Mechanical Demand Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203Thermal Demand Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .204Pulse-Operated Electronic Demand Recorders

Solid-State Demand Recorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .207Electronic Time-of-Use Demand Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .210Electronic Demand Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .211

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KILOVAR AND KILOVOLTAMPERE METERINGKiloVAR and Kilovoltampere Metering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .219Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .220Phasor Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .222Voltampere Metering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .223Electronic KVA Metering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .225How Should Apparent Energy be Measured? . . . . . . . . . . . . . . . . . . . . . . . . . . . . .226Voltampere Reactive Metering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229Electronic Multiquadrant Metering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .243

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SPECIAL METERINGCompensation Metering for Transformer and Line Losses

Why is Compensation Desired? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .249What is Compensation Metering? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .250Transformer Losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .250Line Loss Compensations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .250Transformer Loss Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .250Transformer Loss Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .251Bidirectional Energy Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .251Meter Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .251Transformers with Taps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .252Transformer Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .252Loss Compensation Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .253Loss Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .257Transformer-Loss Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .263Transformer-Loss Compensator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .264Resistor Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .267Solid-State Compensation Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .272Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .272Totalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .273Pulse Totalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .275Pulse Initiators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .275

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Totalizing Relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .279Multi-Channel Pulse Recorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .280Pulse Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .281Pulse-Counting Demand Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .282Notes on Pulse Totalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .282Metering Time-Controlled Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .283Electronic Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .285Kilowatthour Measurements above Predetermined Demand Levels . . . . . . . . .287Load-Study Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .288

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INSTRUMENT TRANSFORMERS

Conventional Instrument TransformersDefinitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .289Basic Theory of Instrument Transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .291Instrument Transformer Correction Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .313Application of Correction Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .324Burden Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .339IEEE Standard Accuracy Classes for Metering . . . . . . . . . . . . . . . . . . . . . . . . . . . .342High-Accuracy Instrument Transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .346Types of Instrument Transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .346Selection and Application of Instrument Transformers . . . . . . . . . . . . . . . . . . . .350Instrument Transformer Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .353Verification of Instrument Transformer Connections . . . . . . . . . . . . . . . . . . . . . .361Instrument Transformer Test Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .365The Knopp Instrument Transformer Comparators . . . . . . . . . . . . . . . . . . . . . . . .376

Optical Sensor SystemsIntroduction to Optical Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .381Optical Current Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .384Sensing Mechanism in Optical Current Sensors . . . . . . . . . . . . . . . . . . . . . . . . . .386Optical Voltage Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .388Sensing Mechanisms in Optical Voltage Sensors . . . . . . . . . . . . . . . . . . . . . . . . . .390Unique Issues for Optical Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .391

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METER WIRING DIAGRAMSIndex for Illustrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .401

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C H A P T E R 1 3

THE CUSTOMERS PREMISES, SERVICE AND INSTALLATIONSThe Customers Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .453Overhead Service to Low Houses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .456Circuit Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .456Grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .458Meter Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .460Meter Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .461The Neutral Wire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .467Meter Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .468Selection of Meter Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .469Meter Sockets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .469Meter Installation and Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .474Inactive and Locked-Out Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .479Test Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .479Instrument Transformer Metering in Metalclad Switchgear . . . . . . . . . . . . . . . .480Pole-Top Metering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .481Good Practices for Metering Personnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .481Guide for Investigation of Customers High-Bill Inquiries on the

Customers Premises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .483Methods Used in Checking Installations for Grounds . . . . . . . . . . . . . . . . . . . . . .485

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ELECTRICITY METER TESTING AND MAINTENANCEElectricity Meter Testing and Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .487Reference Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .488Simultaneous Multifunction Autoranging Standards . . . . . . . . . . . . . . . . . . . . . .488Single-Function Autoranging Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .489Single-Function Manual Ranging Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . .491Rotating Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .491Test Loading Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .492Voltage Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .496Sensors, Counters, and Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .497Basic Induction-Type Watthour Meter Test, Single Stator . . . . . . . . . . . . . . . . . . .500Induction-Type Meter Adjustments, Single Stator . . . . . . . . . . . . . . . . . . . . . . . . .503Multi-Stator Induction-Type Meter Tests and Adjustments . . . . . . . . . . . . . . . . .504Electronic Meter Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .506Meter Test Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .506Rotary Stepping Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .507Electricity Meter Test Fixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .507Shop Test Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .510Testing on Customers Premises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .514Mobile Shop Field Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .521Meter Test by Indicating Wattmeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .522Meter Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .523Watthour Meter Test Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .526

xiv HANDBOOK FOR ELECTRICITY METERING

C H A P T E R 1 5

DEMAND METER TESTING AND MAINTENANCEMechanical Demand Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .529Electronic Demand Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .534Electronic Time-of-Use Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .536Recording Watthour Demand Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .538Pulse-Operated Demand Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .538Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .538Solid-State Pulse Recorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .540Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .540

C H A P T E R 1 6

THE STANDARDS LABORATORYScope and Responsibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .541Standardization and National Metrology Laboratories . . . . . . . . . . . . . . . . . . . . .542Standard Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .543Voltage and Current Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .549Digital Multimeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .550The Chain of Standardization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .550Accuracy Ratios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .552Standard Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .552Random and Systematic Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .553Cross Checks Among Laboratories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .554Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .554Laboratory Location and Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .554Laboratory Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .555

C H A P T E R 1 7

METER READINGMeter Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .557How to Read a Watthour Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .558Register Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .560Meters with Electronic Displays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .561Demand Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .561Automatic Retrieval of Data from Solid-State Recorders . . . . . . . . . . . . . . . . . . .565Electronic Meter Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .565Automatic Meter Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .566

xv

LIST OF TABLES

C H A P T E R 3

MATHEMATICS FOR METERING (A BRIEF REVIEW)Table 3-1. Signs of the Functions of Angles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31Table 3-2. Powers of Ten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33Table 3-3. Relationship of Registration, Percent Error, and Correction Factor . .41

C H A P T E R 4

ELECTRICAL CIRCUITSTable 4-1. Application Frequencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60Table 4-2. Polar and Rectangular Representation of Impedance

of Circuit Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71Table 4-3. Polar and Rectangular Representation . . . . . . . . . . . . . . . . . . . . . . . . . .71Table 4-4. Polar and Rectangular Representation of Current in Parallel Circuit .72Table 4-5. Formulas for Single-Phase AC Series Circuits . . . . . . . . . . . . . . . . . . . . .73

C H A P T E R 1 0

SPECIAL METERINGTable 10-1. Copper-Loss Multipliers for Common Transformer Taps

with Low-Voltage Metering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .252Table 10-2. Compensated Meter Correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .271

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C H A P T E R 1 1

INSTRUMENT TRANSFORMERSTable 11-1. Definitions of Instrument Transformer Ratio,

Ratio Correction Factor, and Related Terms . . . . . . . . . . . . . . . . . . . . . . . . . . .314Table 11-2. Phase Angle Correction Factors (PACFs) . . . . . . . . . . . . . . . . . . . . . . .318Table 11-3. Phase Angle Correction Factors (PACFs) . . . . . . . . . . . . . . . . . . . . . . .320Table 11-4. Summary of Fundamental Relations for Single-Phase

Metering Installations Involving Instrument Transformers . . . . . . . . . . . . . .324Table 11-5. Maximum Percent Errors for Combinations of 0.3% IEEE Accuracy

Class Instrument Transformers under IEEE-Specified Conditions of Burden, and Load Power Factors between 1.00 and 0.6 Lag . . . . . . . . . . . .325

Table 11-6. Calculation of Meter Accuracy Settings . . . . . . . . . . . . . . . . . . . . . . . .327Table 11-7. Average Ratio and Phase Angle Calculation Sheet for

Polyphase Installations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .332Table 11-8. Watthour Meter Test, Combined Error Calculation Sheet for

Three-Stator, Three-Phase Meters Tested Three-Phase Using Three Watthour Standards or Single-Phase Series Using One Watthour Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .333

Table 11-9. Watthour Meter Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .335Table 11-10. Watthour Meter Test, Combined Error Calculation Sheet

for Two-Stator, Three-Phase Meters Tested Three Phase Using Two Watthour Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .337

Table 11-11. Summary of Basic Formulas for Applying Instrument Transformer Corrections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .338

Table 11-12. Methods of Expressing Burdens of Instrument Transformers . . . .340Table 11-13. IEEE Accuracy Classes for Voltage Transformers . . . . . . . . . . . . . . .344Table 11-14. IEEE Standard Burdens for Voltage Transformers . . . . . . . . . . . . . .345Table 11-15. IEEE Accuracy Classes for Meter Current Transformers . . . . . . . . .345Table 11-16. IEEE Standard Burdens for Current Transformers

with 5 Ampere Secondaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .345

C H A P T E R 1 4

ELECTRICITY METER TESTING AND MAINTENANCETable 14-1. Calibrating Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .514

11

CHAPTER

INTRODUCTION TO THE METER DEPARTMENT

THE ELECTRIC UTILITY AND THE COMMUNITY

THE ELECTRIC COMPANY and the community which it serves are perma-nently interdependent. An electric company, by the nature of its business,cannot pick up its generating plant, transmission, or distribution system andmove to some other community. It is firmly rooted where it is located. Its progressdepends to a large extent upon the progress of the area it serves; also, it dependsupon the respect and active support of its customers. It makes good sense for theelectric company to work cordially and cooperatively with its customers towardthe improvement of economic and civic conditions. Because of this, the meterreader or meter technician must be aware that they represent the Companywhen calling on a customers home or business.

What the electric company sells and/or delivers has become essential to thepoint that loss of electric power causes more than inconvenience; it can mean real hardship, even tragedy. In addition, large quantities of electricity cannot be produced and stored and so must be immediately available in sufficient quan-tities upon demand. What this means is that we sell and/or deliver not only thecommodity of electric energy but a very valuable service as well.

The service performed by the electric company and its employees should be so well done that every member of the company and the community can beproud of it.

THE DUTIES OF THE METER DEPARTMENT

The primary function of the meter department is to maintain revenue meteringinstallations at the high level of accuracy and reliability as specified by companyand regulatory requirements. This usually involves the installation, testing, opera-tion, and maintenance of meters and metering systems.

Additional functions, which vary with individual companies, may include:appliance repair, connection of services, testing of rubber protective equipment,stocking and tracking metering equipment, operation of standards laboratories,

2 HANDBOOK FOR ELECTRICITY METERING

manual meter reading, automated meter reading, interval data retrieval and processing, installation and maintenance of advanced meter options, acceptancetesting of material and equipment, instrument calibration and repair, investiga-tion of customer complaints, revenue protection and metering security, instal-lation and maintenance of load survey and load management equipment, relaytesting and high-voltage testing. Although possibly quite removed from metering,these and many similar functions may become the responsibility of the meterdepartment predominantly for two reasons: first, the direct association of thework with metering, as in the case of meter reading, and, second, the characteris-tic ability of meter personnel to translate their knowledge and techniques to other fields requiring detailed electrical knowledge and specialized skills, as in the case of operation of standards laboratories, and instrument repair.

The electric meter, since it generally serves as the basis for customer bill-ing, must be installed, maintained, tested, and calibrated to assure accuracy ofregistration. To accomplish this, the accuracy of all test equipment must be trace-able through suitable intermediate standards to the basic and legal standards ofelectrical measurement maintained by the National Institute of Standards andTechnology (NIST). Quality of workmanship and adherence to procedures mustbe consistently maintained at a level which will achieve this desired accuracy. Poor workmanship or deviation from procedures can have a serious effect on both the customer and the company. Standards, procedures, and instructions are essential to insure uniformity of operations, to prevent errors, and for over-all safety and economy.

CUSTOMER CONTACTS

Because of the electric companys place in the community, and because membersof the meter department may frequently meet customers face-to-face, it is impor-tant that all meter personnel exemplify those qualities of integrity and courtesywhich generate confidence in the company. Day-to-day contacts with customersprovide these employees with exceptional opportunities to serve as good-willambassadors and may earn public appreciation for the services they and theircompany perform. To achieve this appreciation, employees must demonstrate asincere desire to be helpful, as well as high ethical standards in the performance of their work.

In many companies the increase in outdoor meters as well as the imple-mentation of automated meter reading systems, has resulted in a decrease in themeetings between customers and company employees. Therefore, every effortshould be made to take advantage of those opportunities for building good willthat do present themselves in areas other than meter reading.

First impressions are often lasting impressions. It is desirable that meter personnel look their best so that a good image of the company they represent willbe left in the customers mind. Neatness and cleanliness are of utmost importance.The little things which customers notice may have considerable influence on the companys reputation.

Visits to a customers premises for meter reading, testing, or for other reasons,afford opportunities for personnel to demonstrate the companys interest in thecustomers welfare. Courteous consideration of every request will create satisfac-tion and appreciation of the efforts made by the company to render good service.

INTRODUCTION TO THE METER DEPARTMENT 3

However, customers should be referred to the appropriate department or personfor answers to all questions on rates, billing, or any other matter which is outsidethe meter employee's area of expertise. Promises requiring action beyond theemployees own capability should be avoided. In practically all cases, assurancethat any request will be conveyed to the proper party will satisfy the customer.

Upon entering a customers premises, meter personnel should make theirpresence and business known and should cheerfully present identification card, badge, or other credentials when requested. All work done on customerspremises should be planned carefully and carried out promptly. While on cus-tomers premises, conversations between company personnel should be aboutthe work at hand and should not be argumentative.

If utility personnel notice any unusual conditions on the customers premisesor in the immediate vicinity which might affect safety, the companys system, orthe customers electric service, they should report them promptly to their imme-diate supervisors.

Telephone conversations with customers, like premise visits, can go a longway toward expressing the companys interest in the customer if they are con-ducted with intelligence and understanding. Sometimes considerable patiencemay be required, but even then, as at all times, a courteous tone of voice will prove most helpful.

KNOWLEDGE REQUIRED IN METERING

The theory of metering is highly technical. To understand their jobs, meter per-sonnel must have a working knowledge of instruments and meters, elementaryelectricity, elementary mathematics, and certain practical aspects of electric services. A good understanding of electronics and personal computers (PCs) hasbecome a requirement for work on electronic metering equipment, such as programmable electronic meters and interval data recorders. Todays meter technician should be competent in the following subjects:

Math: fractions and decimals necessary to calculate meter constants, registerratios and pulse values.

Electrical circuits: AC and DC circuits with particular reference to Ohms Lawand Kirchhoffs Law.

Inductance, capacitance, power factor, and vector analysis. Electronic components and circuits. PCs, in particular, for communicating with and programming electronic meters. The current-carrying capacity of wire, the relationship between electricity

and heat, and the causes and effects of voltage drops. The principles of indicating instruments. The principles of operation for both electromechanical and electronic

watthour meters, and a good understanding of how to test and calibrate those meters.

Single and polyphase circuits and how to meter them correctly. Blondels Theorem and its application. Principles of power, current, and voltage transformers and how to intercon-

nect them. The correct methods of bonding, grounding, and shielding for both safety

and the protection of electronic equipment.


The application of fuses or circuit breakers. Basic telecommunication principles and practices.

Various books on metering which can be studied to attain technical knowledge are generally made available within the company. There are also manyexcellent instructional books and pamphlets issued by the manufacturers.

Besides the technical subjects mentioned before, effective meter personnelmust be familiar with company policies, procedures, standards, and work prac-tices that relate to metering. They should attain such additional knowledge of electrical engineering, self improvement, and the utility business in general, asopportunities provide. Above all, they must be willing to study and to learn.

METER SECURITY

As the cost of electricity rises to become a significant portion of the cost of living, the temptation to violate the security of metering equipment for the purpose of energy theft becomes irresistible for some. In addition, the possibilityof an organized effort to tamper with metering equipment increases with theincreased cost of energy. Therefore, the meter employee must be aware of the various techniques of energy theft and be constantly on the lookout for such violations. Since meter security systems vary throughout the industry, it becomesnecessary for meter employees to completely familiarize themselves with theircompanys policy for securing meters and associated devices, and to keep con-stant vigil for violations. Incidents of tampering should be reported immediatelyin accordance with company instructions, taking care to preserve all evidence and to submit complete, well documented, and brief reports.

It is imperative to bear in mind that circumstantial evidence of tamperingshould not be interpreted as guilt until all evidence has been examined by thosedesignated to do so. Therefore, courtesy toward all customers, even in strained circumstances, will speak well for you, your department, and your company.

Meter security begins with the seal that secures the glass cover to the base of the meter. This seal is applied without a tool and offers no interference when installing the meter. After the meter is installed, a seal must be applied to secure the meter mounting device whether it is the ring-type or ringless. Ring-type sockets are secured by sealing the ring that holds the meter in place. Ringlesssockets are secured by installing the socket cover after the meter is in place, thensealing the cover hasp.

The demand reset mechanism is another area which needs to be secured with a seal to prevent undetected tampering. It should be sealed each time thedemand is reset. If a different color seal is used each reading cycle, there is assur-ance that the demand was reset at the end of the last cycle.

To be sure your companys sealing program maintains its integrity, sealsshould be treated as security items. Only authorized personnel should have accessto seals, and they should not be left where unauthorized people would come incontact with them.

The most important part of the sealing procedure is the follow-up. Every time the meter is read, the seal should be inspected, not just visually but physi-cally. This seal should be tugged on and visually inspected to make sure there was no tampering and it is the proper seal for that meter. Evidence of tamperingshould be reported immediately.

INTRODUCTION TO THE METER DEPARTMENT 5

There is a wide variety of seals available for all of these applications. Somerequire tools for installation, some do not. Some are all metal, some all plastic, andsome a combination of both. Whatever seal is used, however, it should offer thefollowing benefits:

Be unique to your company and readily identifiable. Be impossible to remove without leaving visible signs of tampering. Be numbered so that particular seals can be identified with the location

or installer.Electronic meters may require software security, i.e., password protection.

Most manufacturers provide for at least two level password protection. These lev-els are particularly useful to allow read only access to the meter by anotherdepartment or company. In this case, one password will allow for reading orretrieving data from the meter and the other password will allow for both readingand writing or programming from/to the meter. It is important to maintain strictsecurity on all metering passwords in accordance with company policy.

SAFETY

Safety is a full-time business and requires the hard work and full cooperation ofevery meter employee. Safety procedures are measures which, if followed, willenable personnel to work without injury to themselves or others and withoutdamage to property.

Simply issuing safety procedures or rules does not guarantee safe work practices or produce good safety records. Meter employees must learn the safetyrules of their company, apply them daily, and become safety-minded.

Meter personnel owe it to themselves, their families, and their company to do each step of every job the safe way. Careful planning of every job is essential.Nothing should be taken for granted. The meter employee must take responsi-bility for his/her own safety. Constant awareness of safety, coupled with training, experience, and knowledge of what to do and how to do it, will preventmost accidents.

Every meter employees attention is directed to the following general sugges-tions, which are almost without exception incorporated in company safety rules:

Horseplay and practical jokes are dangerous. Work safely, consider each act,and do nothing to cause an accident.

Knowledge of safe practices and methods, first aid, and CPR is a must formeter personnel.

Beware of your surroundings and alert to unsafe conditions. Report unsafe conditions or defective equipment to your immediate super-

visor without delay. Have injuries treated immediately. Report all accidents as prescribed by company safety rules. Do a job hazard analysis when appropriate before beginning a job. Re-assess

when something unexpected happens during the job. Exercise general care and orderliness in performance of work. The right way is the safe way. Do not take short cuts. Study the job! Plan ahead! Prevent accidents! Select the right tools for the job and use them properly. Keep tools in good working order.


Use personal protective equipment when appropriate. Exercise good housekeeping at all times. Handle material with care. Lift and carry properly. Respect secondary voltage. It can be fatal. Never substitute assumptions for facts. The importance of working safely cannot be over-emphasized. Safety pays

dividends in happiness to meter personnel and their families. Remember, there is no job so important that it cannot be done in a

safe manner.

7COMMON TERMS USED IN METERING

THE FOLLOWING DEFINITIONS are to be considered as practical, commonunderstandings. In order to keep the explanations as clear and simple as possible, occasional departures from exact definitions have been permitted. Theexplanations given are intended to be useful for meter personnel rather than forscientists. For additional definitions see the current version of ANSI C12.1 Code for Electricity MeteringDefinitions Section, and ANSI/IEEE 100-1988 StandardDictionary of Electrical and Electronics Terms.

A-BaseSee Bottom-Connected Meter.

AccuracyThe extent to which a given measurement agrees with the definedvalue.

AmmeterAn instrument to measure current flow, usually indicating amperes.Where indication is in milliamperes, the instrument may be called a milliammeter.

AmpereThe practical unit of electric current. One ampere is the current causedto flow through a resistance of 1 ohm by 1 volt.

Ampere-HourThe average quantity of electric current flowing in a circuit for onehour.

Ampere-TurnA unit of magnetomotive force equal to that produced by oneampere flowing in a single turn of wire.

AnnunciatorA label that is displayed to identify a particular quantity being shown.

Automatic Meter Reading (AMR)The reading of meters from a location remotefrom where the meter is installed. Telephone, radio, and electric power lines areused to communicate meter readings to remote locations.

AutotransformerA transformer in which a part of the winding is common toboth the input and output circuits. Thus, there is no electrical insulation betweeninput and output as in the usual transformer. Because of this interconnection, caremust be exercised in using autotransformers.

2CHAPTER


Balanced LoadThe term balanced load is used to indicate equal currents in all phases and relatively equal voltages between phases and between each phase and neutral (if one exists), with approximately equal watts in each phase of the load.

Base LoadThe normal minimum load of a utility system; the load which is car-ried 24 hours a day. Plants supplying this load and operating day and night, arespoken of as base-load plants.

Basic Impulse Insulation Level (BIL)A specific insulation level expressed in kilovolts of the crest value of a standard lightning impulse (1.2 50 micro-second wave).

Blondels TheoremIn a system of N conductors, N-l meter elements, properlyconnected, will measure the power or energy taken. The connection must be suchthat all voltage coils have a common tie to the conductor in which there is no cur-rent coil.

Bottom-Connected MeterA meter having a bottom connection terminal assem-bly. Also referred to as an A-base electricity meter.

Bridge, KelvinAn arrangement of six resistors, electromotive force, and a gal-vanometer for measuring low values of resistance. In this bridge a large current ispassed through the unknown resistance and a known low resistance. The galvano-meter compares the voltage drops across these two resistors in a high-resistancedouble ratio circuit made up of the other four resistors. Hence, the bridge is oftencalled a double bridge.

Bridge, WheatstoneAn arrangement of four resistances, one of which may beunknown and one generally adjustable, to which is applied an electromotive force.A galvanometer is used for continually comparing the voltage drops, thereby indi-cating the resistance values.

British Thermal Unit (BTU)A unit of heat. One kilowatthour is equivalent to3,413 BTUs.

BurdenThe load, usually expressed in voltamperes at a specified power factor,placed on instrument transformer secondaries by the associated meter coils,leads, and other connected devices.

CalibrationComparison of the indication of the instrument under test, or regis-tration of meter under test, with an appropriate standard.

CapacitanceThat property of an electric circuit which allows storage of energyand exists whenever two conductors are in close proximity but separated by aninsulator or dielectric material. When direct voltage is impressed on the conduc-tors, a current flows momentarily while energy is being stored in the dielectricmaterial, but stops when electrical equilibrium is reached. With an alternatingvoltage between the conductors, the capacitive energy is transferred to and fromthe dielectric materials, resulting in an alternating current flow in the circuit.

Capacitive ReactanceReactance due to capacitance. This is expressed in ohms.The capacitive reactance varies indirectly with frequency.

COMMON TERMS USED IN METERING 9

Central StationControl equipment, typically a computer system, which cancommunicate with metering and load control devices. The equipment may alsointerpret and process data, accept input from other sources, and prepare reports.

Circuit, Three-WireA metallic circuit formed by three conductors insulatedfrom each other. See Three-Wire System.

Circuit, Two-WireA metallic circuit formed by two adjacent conductors insulated from each other. When serving domestic loads one of these wires is usually grounded.

Circuit BreakerA device, other than a fuse, designed to open a circuit when anoverload or short circuit occurs. The circuit breaker may be reset after the condi-tions which caused the breaker to open have been corrected.

Circular MilThe area of a circle whose diameter is one mil (1/1000 in). It is a unitof area equal to /4 or 0.7854 square mil. The area of a circle in circular mils is,therefore, equal to the square of its diameter in mils.

Class DesignationThe maximum of the watthour meter load range in amperes.

ClearanceShortest distance measured in air between conductive parts.

Clockwise RotationMotion in the same direction as that of the hands of a clock,front view.

ConductanceThe ability of a substance or body to pass an electric current.Conductance is the reciprocal of resistance.

Conductor LossesThe watts consumed in the wires or conductors of an electric circuit. Such power only heats the wires, doing no useful work, so it is aloss. It may be calculated from I2R where I is the conductor current and R is the circuit resistance.

Connected LoadThe sum of the continuous ratings of the connected load-consuming apparatus.

ConstantA quantity used in an equation, the value of which remains the sameregardless of the values of other quantities used in the equation.

Constant, KYZ Output (Ke)Pulse constant for the KYZ outputs of a solid-statemeter, programmable in unit-hours per pulse.

Constant, Mass Memory (Km)The value, in unit quantities, of one increment(pulse period) of stored serial data. Example: Km = 2.500 watthours/pulse.

Constant, Watthour

(a) For an electromechanical meter (Kh): The number of watthours repre-sented by one revolution of the disk, determined by the design of the meterand not normally changed. Also called Disk Constant.(b) For a solid-state meter (Kh or Kt): The number of watthours represented by one increment (pulse period) of serial data. Example: Kh or Kt = 1.8watthours/pulse.

Constant Kilowatthour of a Meter (Register Constant, Dial Constant)The multiplier applied to the register reading to obtain kilowatthours.


Core LossesCore losses usually refer to a transformer and are the watts requiredin the excitation circuit to supply the heating in the core. Core heating is caused by magnetic hysteresis, a condition which occurs when iron is magnetized byalternating current, and by the eddy currents flowing in the iron. Core losses areoften called iron losses.

CreepFor mechanical meters, a continuous motion of the rotor of a meter with normal operating voltage applied and the load terminals open-circuited. Forelectronic meters, a continuous accumulation of data in a consumption registerwhen no power is being consumed.

Creepage DistanceShortest distance measured over the surface of insulationbetween conductive parts.

Current CircuitInternal connections of the meter and part of the measuring element through which flows the current of the circuit to which the meter is connected.

Current CoilThe coil of a watthour meter through which a magnetic field is pro-duced that is proportional to the amount of current being drawn by the customer.

Current TransformerAn instrument transformer designed for the measurementor control of current. Its primary winding, which may be a single turn or bus bar,is connected in series with the load. It is normally used to reduce primary currentby a known ratio to within the range of a connected measuring device.

Current Transformer, Continuous Thermal Current Rating FactorThe factor bywhich the rated primary current is multiplied to obtain the maximum allowableprimary current based on the maximum permissible temperature rise on a con-tinuous basis.

Current Transformer Phase AngleThe angle between the current leaving theidentified secondary terminal and the current entering the identified primary terminal. This angle is considered positive when the secondary current leads theprimary current.

CutoutA means of disconnecting an electric circuit. The cutout generally con-sists of a fuse block and latching device or switch.

CycleOne complete set of positive and negative values of an alternating currentor voltage. These values repeat themselves at regular intervals (See Hertz).

Damping of an InstrumentThe term applied to its performance to denote themanner in which the pointer settles to its steady indication after a change in thevalue of the measured quantity. Two general classes of damped motion are distin-guished as follows:

(a) Under-DampedWhen a meter pointer oscillates about the final positionbefore coming to rest.

(b) Over-DampedWhen the pointer comes to rest without overshooting therest position.

The point of change between under-damped and over-damped is called criticaldamping and occurs when the degree of pointer overshoot does not exceed anamount equal to one half the rated accuracy of the instrument.


Dead-FrontEquipment which, under normal operating conditions, has no liveparts exposed, is called dead-front.

DemandThe average value of power or related quantity over a specified intervalof time. Demand is expressed in kilowatts, kilovoltamperes, kiloVARs, or othersuitable units. An interval may be 1, 5, 10, 15, 30, or 60 minutes.

Demand, Continuous CumulativeThe sum of the previous billing period maxi-mum demands and the present period maximum demand.

Demand, CumulativeThe sum of the previous billing period maximum demandreadings. At the time of billing period reset, the maximum demand for the most recent billing period is added to the previously accumulated total of all maximum demands.

Demand, MaximumThe highest demand measured over a selected period oftime such as one month. Also called Peak Demand.

Demand, Rolling IntervalA method of measuring power or other quantity bytaking measurements within fixed intervals of the demand period. This methodcan be used to determine total demand, average demand, maximum demand, and average maximum demand during the full interval.

Demand, Sliding WindowSee Demand, Rolling Interval.

Demand, Threshold AlertAn output to indicate that a programmed value ofdemand has been exceeded.

Demand Constant (Pulse Receiver)The value of the measured quantity for each received pulse, divided by the demand interval, expressed in kilowatts perpulse, kiloVARs per pulse, or other suitable units. The demand interval must beexpressed in parts of an hour such as 1/4 for a 15 minute interval or 1/12 for a 5 minute interval.

Demand DelayThe programmable amount of time before demand calculationsare restarted after a power outage. Also called Cold Load Pickup and DemandForgiveness.

Demand DeviationThe difference between the indicated or recorded demandand the true demand, expressed as a percentage of the fullscale value of thedemand meter or demand register.

Demand FactorThe ratio of the maximum demand to the connected load.

Demand Interval (Block-Interval Demand Meter)The specified interval of timeon which a demand measurement is based. Intervals such as 10, 15, or 60 minutesare commonly specified.

Demand Interval SynchronizationPhysical linking of meters to synchronize the demand intervals of all meters. Also called Demand Timing Pulse.

Demand MeterA metering device that indicates or records the demand, maximum demand, or both. Since demand involves both an electrical factor anda time factor, mechanisms responsive to each of these factors are required as well as an indicating or recording mechanism. These mechanisms may be sepa-rate or structurally combined with one another.


Demand Meter, IndicatingA demand meter equipped with a readout that indi-cates demand, maximum demand, or both.

Demand Meter, Integrating (Block-Interval)A meter that integrates power or arelated quantity over a fixed time interval and indicates or records the average.

Demand Meter, LaggedA meter that indicates demand by means of thermal ormechanical devices having an approximately exponential response.

Demand Meter, Time Characteristic (Lagged-Demand Meter)The nominal timerequired for 90% of the final indication, with constant load suddenly applied. Thetime characteristic of lagged-demand meters describes the exponential responseof the meter to the applied load. The response of the lagged-demand meter to theload is continuous and independent of selected discrete time intervals.

Demand Meter, Timing DeviationThe difference between the elapsed time indicated by the timing element and the true elapsed time, expressed as a percentof the true elapsed time.

Demand RegisterA mechanism for use with an integrating electricity meter thatindicates maximum demand and also registers energy (or other integrated quantity).

Demand-Interval DeviationThe difference between the measured demandinterval and the specified demand interval, expressed as a percentage of the spec-ified demand interval.

DetentA device installed in a meter to prevent reverse rotation (or meter registration).

Dial-Out CapabilityAbility of a meter to initiate communications with a cen-tral station.

Disk ConstantSee Constant, Watthour (a).

Disk Position Indicator, or CaterpillarAn indicator on the display of a solid-state register that simulates rotation of a disk at a rate proportional to power.

DisplayA means of visually identifying and presenting measured or calculatedquantities and other information. (Definition from ANSI C12.1.)

DiversityA result of variation in time of use of connected electrical equipmentso that the total maximum demand is less than the sum of the maximum demandsof the individual units.

Eddy CurrentsThose currents resulting from voltages which are introduced in a conducting material by a variation of magnetic flux through the material.

Effective ResistanceEffective resistance is equal to watts divided by the squareof the effective value of current.

Effective Value (Root-Mean-Square Value)The effective value of a periodicquantity is the square root of the average of the squares of the instantaneous value ofthe quantity taken throughout one period. This value is also called the root-mean-square value and is the value normally reported by alternating current instruments.

Electrical DegreeThe 360th part of one complete alternating current cycle.

Electricity MeterA device that measures and records the summation of an elec-trical quantity over a period of time.


ElectromagnetA magnet in which the magnetic field is produced by an electriccurrent. A common form of electromagnet is a coil of wire wound on a laminatediron core, such as the voltage coil of a watthour meter stator.

Electromechanical MeterA meter in which currents in fixed coils react with thecurrents induced in the conducting moving element, generally a disk(s), whichcauses their movement proportional to the energy to be measured. Also calledinduction watthour meter.

Electromotive Force (EMF)The force which tends to produce an electric currentin a circuit. The common unit of electromotive force is the volt.

ElementA combination of a voltage-sensing unit and a current-sensing unitwhich provides an output proportional to the quantities measured.

Embedded CoilA coil in close proximity to, and nested within, a current circuitloop of a meter used to measure the strength of a magnetic field and develop avoltage proportional to the flow of current.

Embedded SystemA microcomputer system including microprocessor, memo-ry, power supply, and supporting input and output devices, usually designed for a dedicated application.

EnergyThe integral of active power with respect to time.

FaradThe practical unit of capacitance. The common unit of capacitance is themicrofarad.

Field, MagneticA region of magnetic influence surrounding a magnet or a con-ductor carrying electric current.

Field, StrayUsually a disturbing magnetic field produced by sources external orforeign to any given apparatus.

FirmwareComputer programs used by embedded systems and typically storedin read-only memories. See Memory.

Full LoadA current level for testing the accuracy of a watthour meter, typicallyindicated on a meter by the abbreviation TA, for test amps.

GalvanometerAn instrument for indicating a small electric current.

Gear RatioThe number of revolutions of the rotating element of a meter com-pared to one revolution of the first dial pointer.

GroundA conducting connection, whether intentional or accidental, betweenan electric circuit or equipment and earth.

Ground Return CircuitA current in which the earth is utilized to complete thecircuit.

Grounding ConductorA conductor used to connect any equipment device orwiring system with a grounding electrode or electrodes.

Grounding ElectrodeA conductor embedded in the earth which has conductorsconnected to it to (1) maintain a ground potential and (2) to dissipate current intothe earth.

HenryThe practical unit of inductance. The millihenry is commonly encoun-tered. The common unit of inductance is the millihenry.


Hertz (Cycles per Second)The practical unit of frequency of an alternating current or voltage. It is the number of cycles, sets of positive and negative values,occurring in one second.

HorsepowerA commercial unit of power equal to the average rate of doing work when 33,000 pounds are raised one foot in one minute. One horsepower isapproximately equal to 746 watts.

Hot-Wire InstrumentAn electrothermic instrument whose operation dependson the expansion by heat of a wire carrying the current which produces the heat.

Hybrid MeterA watthour meter with electromechanical and solid-state components.

Hysteresis LossThe energy lost in a magnetic core due to the variation of magnetic flux within the core.

ImpedanceThe total opposing effect to the flow of current in an alternating current circuit. It may be determined in ohms from the effective value of the totalcircuit voltage divided by the effective value of total circuit current. Impedancemay consist of resistance or resistance and reactance.

Induced CurrentA current flow resulting from an electromotive force induced in a conductor by changing the number of lines of magnetic force linking the conductor.

InductanceThat property of an electric circuit which opposes any change ofcurrent through the circuit. In a direct current circuit, where current does notchange, there is no inductive effect except at the instant of turn-on and turn-off.However, in alternating current circuits the current is constantly changing, so theinductive effect is appreciable. Changing current produces changing flux which, in turn, produces induced voltage. The induced voltage opposes the change inapplied voltage, hence the opposition to the change in current. Since the cur-rent changes more rapidly with increasing frequency, the inductive effect alsoincreases with frequency.

Inductance, MutualIf the current change causes induced voltage and an opposing effect in a second conductor, there is mutual inductance.

Inductance, SelfIf the preceding effect occurs in the same conductor as that carrying the current, there is self-inductance. The self-inductance of a straightconductor at power frequency is almost negligible because the changing flux will not induce any appreciable voltage, but self-inductance increases rapidly ifthe conductor is in the form of a coil and more so if the coil is wound on iron.

InductiveHaving inductance, e.g., inductive circuit and inductive load. Cir-cuits containing iron or steel that is magnetized by the passage of current are highly inductive.

Inductive ReactanceReactance due to inductance expressed in ohms. Theinductive reactance varies directly with the frequency.

Instrument TransformerA transformer that reproduces in its secondary circuitin a definite and known proportion, the voltage or current of its primary circuitwith the phase relation substantially preserved.


Instrument Transformer, Accuracy ClassThe limits of transformer correctionfactor in terms of percent error, that have been established to cover specific per-formance ranges for line power factor conditions between 1.0 and 0.6 lag.

Instrument Transformer, Accuracy Rating for MeteringThe accuracy classtogether with the standard burden for which the accuracy class applies.

Instrument Transformer, BurdenThe impedance of the circuit connected to the secondary winding. For voltage transformers it is convenient to express theburden in terms of the equivalent voltamperes and power factor at its specifiedvoltage and frequency.

Instrument Transformer, Correction FactorThe factor by which the reading of a wattmeter or the registration of a watthour meter must be multiplied to correctfor the effects of the error in ratio and the phase angle of the instrument trans-former. This factor is the product of the ratio and phase-angle correction factorsfor the existing conditions of operation.

Instrument Transformer, Marked RatioThe ratio of the rated primary value tothe rated secondary value as stated on the name-plate.

Instrument Transformer, Phase AngleThe angle between the current or voltageleaving the identified secondary terminal and the current or voltage entering the identified primary terminal. This angle is considered positive when the sec-ondary circuit or voltage leads the primary current or voltage.

Instrument Transformer, Phase Angle Correction FactorThe factor by whichthe reading of a wattmeter or the registration of a watthour meter, operated from the secondary of a current transformer, or a voltage transformer, or both,must be multiplied to correct for the effect of phase displacement of secondarycurrent, or voltage, or both, with respect to primary values. This factor equals the ratio of true power factor to apparent power factor and is a function of both the phase angle of the instrument transformer and the power factor of the primarycircuit being measured.

Instrument Transformer, Ratio Correction FactorThe factor by which themarked ratio of a current transformer or a voltage transformer must be multipliedto obtain the true ratio. This factor is expressed as the ratio of

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