Table Of ContentIEEE Std C37.102-1995
(Revision of
IEEE Std C37.102-1987)
IEEE Guide for
AC Generator Protection
Sponsor
Power System Relaying Committee
of the
IEEE Power Engineering Society
Approved 12 December 1995
IEEE Standards Board
Abstract: A review of the generally accepted forms of relay protection for the synchronous gener-
ator and its excitation system is presented. This guide is primarily concerned with protection against
faults and abnormal operating conditions for large hydraulic, steam, and combustion-turbine
generators.
Keywords: ac generator protection, relay protection, synchronous generator
The Institute of Electrical and Electronics Engineers, Inc.
345 East 47th Street, New York, NY 10017-2394, USA
Copyright ' 1996 by the Institute of Electrical and Electronics Engineers, Inc.
All rights reserved. Published 1996. Printed in the United States of America.
ISBN 1-55937-711-9
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Introduction
(This introduction is not part of IEEE Std C37.102-1995, IEEE Guide for AC Generator Protection.)
IEEE Std C37.102 was initially published in 1987. It was subsequently reaf(cid:222)rmed in 1990. The guide is
designed for the protection of typical stream, hydraulic, and combustion-turbine generators. Any scheme
that is judged to be a good alternative practice for generator protection is included in the guide. New
schemes that have gained acceptance and usage have been added to the guide.
In the revision of IEEE Std C37.102-1987, several areas were improved. Among the most notable are as
follows:
(cid:209) The protection of generators for inadvertent energizing has been updated and includes new, widely
used schemes.
(cid:209) The voltage transformers clause has been changed to improve the description of ferroresonance pre-
vention and the addition of two schemes that use current limiting resistors.
(cid:209) A gas turbine protection scheme and power transformer protection through mechanical fault detec-
tion have been added to the guide.
(cid:209) The guide has been revised to align with IEEE Std C37.101-1993, IEEE Guide for Generator Ground
Protection.
(cid:209) The tripping modes described in clause 6 have been rewritten to re(cid:223)ect the current industry practices.
(cid:209) The references and bibliography have been updated. Text and (cid:222)gures have been generally revised for
improved readability and technical enhancement.
(cid:209) The generator motoring protection has been revised to remove those devices used for control logic
purposes rather than protection purposes.
(cid:209) The synchronizing subclause has been expanded to include more details on acceptable synchronizing
limits.
At the time this guide was completed, the Revision of AC Generator Protection Guide Working Group had
the following membership:
William P. Waudby, Chair
Hardy J. King, Vice Chair
T. R. Beckwith R. W. Haas G. R. Nail
W. A. Elmore W. Hartmann A. C. Pierce
E. C. Fennell R. Hedding P. W. Powell
D. J. Finley J. Horwath V. Rebbapragada
J. D. Gardell K. C. Kozminski D. W. Smaha
M. R. Gonzalez S. Mazumdar C. L. Wagner
C. H. Grif(cid:222)n C. J. Mozina M. Yalla
The following persons were on the balloting committee:
Mark Adamiak E. C. Fennell K. K. Mustaphi
John Appleyard C. W. Fromen George R. Nail
E. A. Baumgartner Jonathan D. Gardell B. D. Nelson
Barbara L. Beckwith Jeffrey G. Gilbert G. C. Parr
R. W. Beckwith A. T. Giuliante Robert D. Pettigrew
G. Benmouyal S. E. Grier Arun G. Phadke
David C. Blackburn, Jr. Edward M. Gulachenski Alan C. Pierce
John Boyle E. A. Guro John M. Postforoosh
B. Bozoki R. W. Haas M. S. Sachdev
James A. Bright R. E. Hart Evan T. Sage
J. Burnworth Irwin Hasenwinkle Miriam P. Sanders
H. J. Calhoun C. F. Henville James E. Stephens
Carlos H. Castro J. W. Hohn W. M. Strang
Thomas W. Cease J. D. Huddleston M. J. Swanson
John W. Chadwick, Jr. J. W. Ingleson Richard P. Taylor
S. R. Chano J. A. Jodice James Teague
Graham.Clough Edward W. Kalkstein John T. Tengdin
Stephen P. Conrad Mladen Kezunovic James S. Thorp
Mark W. Conroy K. J. Khunkhun Demetrios A. Tziouvaras
Carey J. Cook W. C. Kotheimer Joe T. Uchiyama
Albert N. Darlington P. A. Kotos E. A. Udren
Douglas C. Dawson John R. Linders Vid. Varneckas
R. W. Dempsey W. J. Marsh, Jr. Charles L. Wagner
C. L. Downs J. E. McConnell William P. Waudby
Paul R. Drum M. J. McDonald Thomas E. Wiedman
Lavern L. Dvorak J. L. McElray P. B. Winston
Walt Elmore M. Meisinger K. Zimmerman
A. Elneweihi William M. Mello J. A. Zipp
J. Esztergalyos G. L. Michel Stan Zocholl
H. G. Farley R. J. Moran John A. Zulaski
Charles J. Mozina
When the IEEE Standards Board approved this standard on 12 December 1995, it had the following
membership:
E. G. (cid:210)Al(cid:211) Kiener, Chair Donald C. Loughry, Vice Chair
Andrew G. Salem, Secretary
Gilles A. Baril Jim Isaak Marco W. Migliaro
Clyde R. Camp Ben C. Johnson Mary Lou Padgett
Joseph A. Cannatelli Sonny Kasturi John W. Pope
Stephen L. Diamond Lorraine C. Kevra Arthur K. Reilly
Harold E. Epstein Ivor N. Knight Gary S. Robinson
Donald C. Fleckenstein Joseph L. Koep(cid:222)nger* Ingo R=FCsch
Jay Forster* D. N. (cid:210)Jim(cid:211) Logothetis Chee Kiow Tan
Donald N. Heirman L. Bruce McClung Leonard L. Tripp
Richard J. Holleman Howard L. Wolfman
*Member Emeritus
Also included are the following nonvoting IEEE Standards Board liaisons:
Satish K. Aggarwal
Steve Sharkey
Robert E. Hebner
Chester C. Taylor
Rochelle L. Stern
IEEE Standards Project Editor
Contents
CLAUSE PAGE
1. Overview..............................................................................................................................................1
1.1 Scope............................................................................................................................................1
1.2 Description of the guide...............................................................................................................1
2. References............................................................................................................................................2
3. Description of generators, excitation systems and generating station arrangements...........................3
3.1 Generator winding design and arrangements...............................................................................3
3.2 Generator grounding....................................................................................................................4
3.3 Excitation systems.......................................................................................................................7
3.4 Generating station arrangements................................................................................................10
4. Protection requirements.....................................................................................................................14
4.1 Generator stator thermal protection...........................................................................................14
4.2 Field thermal protection.............................................................................................................17
4.3 Generator stator fault protection................................................................................................20
4.4 Generator rotor (cid:222)eld protection.................................................................................................46
4.5 Generator abnormal operating conditions..................................................................................51
4.6 System backup protection..........................................................................................................72
4.7 Generator breaker failure protection..........................................................................................76
4.8 Excitation System Protection.....................................................................................................79
4.9 Power transformer protection through mechanical fault detection............................................81
5. Other protective considerations.........................................................................................................82
5.1 Current transformers..................................................................................................................82
5.2 Voltage transformers..................................................................................................................83
5.3 Protection during start-up or shut-down....................................................................................87
5.4 Inadvertent energizing................................................................................................................90
5.5 Subsynchronous resonance........................................................................................................93
5.6 Transmission line reclosing near generating stations................................................................94
5.7 Synchronizing ...........................................................................................................................85
6. Protection speci(cid:222)cation......................................................................................................................96
6.1 Protective arrangements.............................................................................................................96
6.2 Protective functions....................................................................................................................97
ANNEX
A (informative) Bibliography...................................................................................................................110
v
IEEE Guide for AC Generator Protection
1. Overview
1.1 Scope
sihT noitacilppa ediug rof eht yaler noitcetorp fo suonorhcnys srotarenegstneserp yllareneg eht fo weiver a
detpecca dna syaler fo esu eht sezirammus tI .metsys noitaticxe sti dna rotareneg eht rof noitcetorp fo smrof
,secived dna sevres sa a ediug rof eht noitceles fo tnempiuqe ot niatbo etauqeda .noitcetorp ehT ediugsi
primarily concerned with protection against faults and abnormal operating conditions for large hydraulic,
steam, and combustion-turbine generators. esuaceb tluciffid si ezis enihcam no noitcetorp rotareneg gnisaB
the naht metsys rewop eht ot rotareneg eht fo ecnatropmi eht yb erom denimreted eb yam noitcetorp derised
yb e hetzi. srfoot aerhetneg
The recommendations made pertain to typical generator installations. However, sufficient background
information relating to protection requirements, applications, and setting philosophy is given to enable the
redaer ot etaulav eeht deen ot tceles dna yl penploabiattcieut sorropf .tssnoomitautis
The -rossecorporcim lanoitcnuf-itlum a htiw detnemelpmi eb yam ediug siht ni dessucsid snoitcnuf evitcetorp
desab noitcetorp metsys latigid( .)metsys ehT noitcetorp ,yhposolihp ,secitcarp dna stimil erayllaitnesse
identical to those of the implementation using discrete component relays. The algorithms used to perform
emos eht ,revewoH .noitcetorp retteb ro lauqe ecudorp dluohs tub ,tnereffid eb yam snoitcnuf noitcetorp eht fo
ecnamrofrep dna ytilibapac yam eb roirepus gnisueht esnopser ycneuqerf devorpmi sa hcus smetsys latigid
(bandwidth) and thresholds (pickup settings). Other additional features that enhance the functionality may
.sm eltas t y eiesmsgloeibrhdaft leibava
This ybdnatS .noitautis yreve ni srotareneg lla fo stnemeriuqer evitcetorp eht liated ot troprup ton seod ediug
.de dyulllcax cesir f oeiytrcc aaenerp esesdgunnreaegme
1.2 Description of the guide
Clause 3: Description of generators, excitation systems, and generating station arrangements. esualC3
presents a brief description of typical generator design and connections, generator grounding practices,
excitation systems design, and generating station arrangements. The intent of this clause is to present
information that affects the protection arrangement and selection of protective relays.
eseht no stluaf dna noitareposim fo stcapmi evitagen elbissopA eht dna refsnart metsys yrailixua fo noissucsid
smetsys si ton dedulcni ni siht.esualc
The methods employed for grounding and fusing the secondary circuits of voltage transformers and the
sdohtem installations.all for same the generally not are circuits secondary current-transformer grounding for
1
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5991-201.73C dtS IGEUEFIEOD RE
roF this reason, no secondary fuses or ground points are indicated in the figures throughout this guide.
,revewoH EEEI htiw ecnadrocca ni dednuorg eb dluohs stiucric yradnoces remrofsnart egatlov dna tnerruc lla
Std C57.13.3-1983. 1
Clause 4: Protection requirements. esualC 4 y lsfeebiirrbcs eedh tgni gsatmcaedffe fo stluaf dnalamronba
gnitarepo snoitidnoc dna eht epyt fo secived dnarieht A .snoitidnoc eseht tceted ot desu ylnommoc sgnittes
clear deen eht gnitaulave ni redaer eht tsissa lliw srotareneg no seitilamronba fo stceffe eht fo gnidnatsrednu
for, and the means of, obtaining adequate generator protection in any specific situation.
Clause 5: Other protective considerations. esualC 5 stneserp a noissucsi dfo rehto smrof f onoitcetordpna
factors that may be considered in the generator zone.
Clause 6: Protection specifications. Clause 6 presents detailed tabulations and diagrams that are classified
according wohs smargaid dna selbat esehT .metsys eht ot detcennoc si rotareneg eht hcihw yb dohtem eht ot
the combination of relays (and their control function) often applied for generator and excitation system
noitcetorp in accordance with good engineering practices. These tables and diagrams also consider the
evitcetorp tuhs ro pirt ot detcennoc era taht noitats gnitareneg eht ot tnecajda ro ni tnempiuqe rehto no secived
down the generator.
2. References
This era sdradnats gniwollof eht nehW .snoitacilbup gniwollof eht htiw noitcnujnoc ni desu eb llahs dradnats
dedesr eypbus ,ndnaeovios r iepnvhpoetair slilva.ehyrslppa
ISNA C50.12-1982 (Reaff 1989), American National Standard Requirement for Salient-Pole Synchronous
Generators and Generator/Motors for Hydraulic Turbine Applications. 2
ISNA C50.13-1989, American National Standard Requirement for Rotating Electrical Machin-
.ls arscou itorranodrotneroinhRlecyGnCy—Syre
IEEE Std 67-1990, IEEE Guide for Operation and Maintenance of Turbine Generators (ANSI). 3
IEEE Std 142-1991, IEEE Recommended Practice for Grounding of Industrial and Commercial Power
.)IS NsAm(etsyS
IEEE -tinU deleuF-lissoF fo lortnoC dna ,gnikcolretnI ,noitcetorP rof ediuG EEEI ,)2991 ffaeR( 5891-205 dtS
detcennoC maetS snoitatS.)ISNA(
IEEE Std C37.101-1993, IEEE Guide for Generator Ground Protection (ANSI).
IEEE gnitareneG rewoP rof noitcetorP ycneuqerF-lamronbA rof ediuG EEEI ,)2991 ffaeR( 7891-601.73C dtS
Plants (ANSI).
IEEE Std C57.13-1993, IEEE Standard Requirements for Instrument Transformers (ANSI).
1 nrooiFtamro f,nnsoiecner eefeesr esualc.2
2ISNA ,teertS dn24 tseW 11 ,etutitsnI sdradnatS lanoitaN naciremA ,tnemtrapeD selaS eht morf elbaliava era snoitacilbup
, ,,. rwk 6AhoerY3StoNoN0U3lY01F1
3EEEI publications are available from the Institute of Electrical and Electronics Engineers, 445 Hoes Lane, P.O. Box
, 1,.3yA3aS1 wU-Ja 5Nt,5a18c38s30i1P
2
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ACG ENERATORP ROTECTION 5991-201.73C dtS
IEEE SecondaryTransformer Instrument of Grounding the for Guide IEEE 1991), (Reaff C57.13.3-1983 Std
Circuits and Cases (ANSI).
IEEE ,smetsyS ytilitU lacirtcelE ni gnidnuorG lartueN fo noitacilppA eht rof ediuG EEEI ,9891-2.29.26C dtS
gtnriadPnuorG —fsIou Iornootra hrscemnneyetSGs.y)SISNA(
3. Description of generators, excitation systems, and generating station
arrangements
3.1 Generator winding design and arrangements
The nrut-itlum ro nrut-elgnis fo rebmun a fo tsisnoc rotareneg suonorhcnys esahp-eerht a fo sgnidniw rotats
slioc that are connected in a series to form a single-phase circuit. One of these circuits or several circuits
detcennoc detcennoc yllamron era sgnidniw esahp ehT .gnidniw esahp etelpmoc a mrof ot desu era lellarap ni
desu era sgnidniw esahp detcennoc-atleDi .ecnadnepmi lanretxe emos hguorht dednuorg lartuen eht htiw eyw
y ltsluiabhntoisacco is not a common connection. Figure 3.1 illustrates the possible winding arrangements
and connections.
The lla rof desu ylnommoc tsom snoitarugifnoc eht era )b dna )a1.3 serugif ni nwohs stnemegnarra gnidniw
lliw stiucric eseht ,)b1.3 erugif ni nwohs sa esahp rep desu si tiucric eno naht erom nehW .srotareneg fo sepyt
eb connected in parallel inside the machine with two leads being brought out to external connections. In
general, utp to h receu rrenttr ansformercsa bnpe r ovideadet a cehn odtf h peh aswei ndinfgo rre layinagn d
instrumentation purposes.
fo tsisnoc yam tiucric hcae dna esahp rep stiucric fo rebmun a eb yam ereht ,sngised rotarenegordyh emos nI
a number of multi-turn coils connected in series. In these machines, the parallel-connected circuits may be
demrof into two groups that are paralleled with only two leads being brought out to external connections.
There cantransformers current design, this In group. each in circuits of number unequal or equal an be may
be provided in each phase group and in the leads to the external connections.
Figure enibrut-maets egral ni desu semitemos noitcurtsnoc gnidniw-elbuod detcennoc-eyw eht setartsulli )c1.3
generators. .snoitcennoc eyw owt mrof ot yllanretxe detcennoc era taht sgnidniw etarapes owt sah esahp hcaE
The high-voltage terminals of each phase are connected in parallel to form a single three-phase output.
ds en emonrrioaeot hfcet etenaynrwoacpeS yllacisyhp eb yam slartuen esehT .gnidniw hcae fo dne lartuen
at opposite ends of the machine. This arrangement is sometimes referred to as the double-ended, twelve-
bushing machine and is used where ccufarcucrteralutropxeplrhythcna-reiaaetbtle nlse ihong edleat si d t y
of a single bushing. The bushings at each end of the winding can accomcmtut ohrrdrraaeentense tf ormers.
In the delta-connected generator, there may be one or more paralleled circuits per phase with two leads
hcae fo sdne eht ta ,atled eht edisni dedivorp eb nac sremrofsnart tnerruC .snoitcennoc lanretxe ot tuo thguorb
winding, or outside the delta, or both.
3.2 Generator grounding
It is common practice to ground all types of generators through some form of external impedance. The
esoprup of this grounding is to limit the mechanical stresses and fault damage in the machine, to limit
transient voltages during faults, and to provide a means for detecting ground faults within the machine. A
etelpmoc noissucsid fo lla gnidnuorgdna dnuorg noitcetorp sdohtem yam eb dnuof ni EEEI dtS-2.29.26C
1989 and IEEE Std C37.101-1993.
3
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5991-201.73C dtS IGEUEFIEOD RE
Figure 3.1—Winding configurations
The sdohtem tsom ylnommoc desu rof rotareneg gnidnuorg lliw eb dessucsid ni siht .ediug yehT eradetsil
:s egni nir ri oduwegaooheoflttrlabocf
a) High-impedance grounding
)b ecnatsiser-woLgnidnuorg
)c Reactance grounding
d) Grounding-transformer grounding
4
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ACG ENERATORP ROTECTION 5991-201.73C dtS
diloS lacinahcem hgih ni tluser nac ecitcarp siht ecnis desu yllareneg ton si lartuen rotareneg a fo gnidnuorg
sesserts sesserts mumixam eht ,9891-31.05C ISNA ot gnidroccA .enihcam eht ni egamad tluaf evissecxe dna
that a g eneratori sn ormallyd esignedt ow ithstandi st hata ssociatedw itht hec urrentso fa t hree-phasef ault
at eht enihcam .slanimret esuaceB fo eht ylevitaler wol ecneuqes-orez ecnadepmi tnerehni nitsom
suonorhcnys currentswinding produce will terminals machine the at fault phase-to-ground solid a generators,
that are higher than those for a three-phase fault. Therefore, to comply with this guide, generators shall be
grounded msiauannc lnh tie omrt mi hatex impuhma se-to-groufnaduc lutrm raaegt nnoti tuedqeut oaorl,
less than, the three-phase fault current.
Generators phase-ttfhoae-lu gilgrmtaroipeutpansrtd ol tayhuc oinhpsg We rhrooiaufltnteede den d n.o t are
currents, traophnvriseogirdhevcu nodactlune tr amiganiecgtsh t ihnceeo ,n staedonqla duim emanigttels y
faults and also makes the fault location difficult to determine.
The gniwollof sesualcbus edivorp a yrev feirb noitpircsed dna lacipyt snoitacilppa fo eht evobagnidnuorg
methods.
3.2.1 High impedance grounding
Two types of high-impedance grounding are in common use today as discussed in 3.2.1.1 and 3.2.1.2.
3.2.1.1 High-resistance grounding
In this method, a distribution transformer is connected between the generator neutral and ground, and a
resistor yllausu si remrofsnart noitubirtsid eht fo gnitar egatlov yramirp ehT .yradnoces eht ssorca detcennoc si
equal to, or greater than, rated generator line-to-neutral voltage, while the secondary winding rating is 120
V or 240 V. The secondary resistor is selected so that for a single-phase-to-ground fault at the generator
terminals, the power dissipated in the resistor is equal to, or greater than, three times the zero-sequence
eviticapac eht ot detcennoc eb yam taht tnempiuqe rehto lla fo dna ,sgnidniw rotareneg eht fo dnuorg ot AVk
machine terminals. With this resistor rating, the transient overvoltages during faults will be kept to safe
.seulav cosniahsnriigrgdlahiTeen-shr-gtr aiepehe sdhmes g aeirsnsoetFtua- o anttrnd o cfi-eang ugrl.ot u nd
machine terminals, the primary fault current will de toeit bm eiau lln e aieg tvhnfutaoo rb3a A ot 52 .AfI
,elbissop fo )desu nehw( sesuf yramirp eht htiw etanidrooc ot nesohc eb dluohs level tnerruc tluaf dnuorg eht
eyw-eyw connected voltage transformers with grounded neutrals. Note that distribution transformers with
internal fuses or circuit gnidnuor geh tdn anep oe byltnetrevdan idluo cyeh ts a,des ue bto ndluoh ssrekaer b
dnnoait ceemteohrc psdluoc eevbitarep otnai eht emit fo.tluaf
In some cases, the distribution transformer is omitted and a high value of resistance is connected directly
neewteb the generator neutral and ground. The resistor size is selected to limit ground-fault current to the
range of 3–25 A. While this method of grounding is used in Europe, the physical size of the resistors, the
required resistor insulation level, and the cost may preclude the use of this method.
3.2.1.2 Ground fault neutralizer grounding (tuned inductive reactor)
In this grounding method, a distribution-type transformer with a ratio selected as above is used with a
yradnoces otni detcelfer nehw ,taht os detceles si rotcaer yradnoces siht fo eulav cimho ehT .rotcaer elbanut
the primary circuit, its reactance is equal to one-third of the zero-sequence capacitive reactance of the
generator and all equipment connected to the generator terminals up to and including the delta-connected
windings -esahp-elgnis eht stimil gnidnuorg fo epyt sihT .sremrofsnart ecivres noitats dna pu-pets niam eht fo
to-ground fault current to 1 A or less. This low fault current will not sustain an arc or cause damage to the
generator whereinstallations unit-system all with used be can grounding neutralizer fault Ground iron. stator
a single generator is connected through its individual grounded wye-delta step-up transformer (or
)sremrofsnart ot eht.metsys
5
