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CECW-EP
Engineer
Manual
1110-2-3006
Department
of
th e
Army
U.S.
Army
Corps
ofEngineers
Washington,
DC
20314-1000
EM
1110-2-3006
30June1994
Engineering
andDesign
HYDROELECTRIC
P OW E RPLANTS
ELECTRICALDESIGN
DistributionRestriction
Statement
Approved fo r
public
release;
distributionis
unlimited.
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CECW-EP
Manua l
No .
1110-2-3006
D E P A R T M E N TOF
THE
ARMY
U.S .
A r m y
Corps
of
E n g i n e e r s
Washington,
DC0314 -1000
EM
1110-2-3006
30
June1994
E n g i n e e r i n g
an d
Design
H Y D R O E L E C T R I CP O W E R
PLANTS
E L E C T R I C A L
D E S I G N
1 .urpose .
hismanualprovidesguidanceandassistancetodesignengineersin
the
developmentof
electricaldesignsfo r
new
hydroelectric
power
plants.
2 .
pplicability.
hi s
manual
is
applicable
to
al l
civil
works
activities
having
responsibilities
fo r
the
design
of
hydroelectric
power
plants.
FO R
THE
C OM M ANDER:
WILLIAMD.B R O W N
Colonel,
Corps
of
Engineers
Chief
of Staff
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CECW-EP
M a n u a l
No.
1110 -2 -3006
DEP ARTMENT
OF
TH E
A R M Y
U.S.
ArmyCorps
ofEng inee rs
Washington,DC0314-1000
E M1110 -2 -3006
30J u n e1994
Engineer ing
an d
Design
HYDROELECTRICPOWER
PLANTS
ELECTRICALDESIGN
TableofContents
Sub ject
aragraph
Chapter1
Introduction
Purpose
- 1
Applicability
-2
References -3
Scope
-4
Codes -5
Criteria -6
Hydroelectric
Design
Center
-7
Chapter
2
Basic
Switching
Provisions
One-Line
Diagrams -1
Plant
Scope
-2
UnitSwitching
Arrangements
-3
Substation
Arrangements
-4
FaultCurrent
Calculations
-5
Chapter
3
Generators
General -1
Electrical
Characteristics
-2
Generator
Neutral
Grounding
-3
Generator
SurgeProtection
-4
Mechanica l
Characteristics
-5
Excitation
Systems-6
Generator
Stator -7
Rotoran dShaft
-8
Brakes
and
Jacks-9
Bearings -1 0
Temperature
Devices
-1 1
Final
Acceptance
Tests
-12
Fire
SuppressionSystems
-1 3
Chapter4
PowerTransformers
General -1
Page
2-1
2-1
2- 2
2- 3
2- 3
3-1
3-1
3- 6
3- 8
3- 8
3-10
3-14
3-15
3-15
3-15
3-16
3-17
3-18
4-1
Sub ject aragraph
Rating
-2
Cooling -3
Electrical
Characteristics
-4
Terminals
-5
Accessories -6
Oil
Containment
Systems
-7
FireSuppression
Systems
-8
Chapter
5
High
VoltageSystem
Definition
-1
Switchyard
-2
Switching
Scheme
-3
Bus
Structures
-4
Switchyard Materials
-5
Transformer
Leads
-6
Powerhouse
-
Switchyard
Power
Controlan d
Signal
Leads
-7
Circuit
Breakers
-8
Disconnect
Switches
-9
Surge
Arresters
-1 0
Chapter6
Generator-VoltageSystem
General
-1
GeneratorLeads -2
NeutralGrounding
Equipment
-3
InstrumentTransformers
-4
Single
Unit
an dSmall
Power
Plant
Considerations
-5
Excitation
System
Power
Potential
Transformer
-6
CircuitBreakers
-7
Chapter7
StationServiceSystem
Power
Supply
-1
Page
4-1
4-1
4-2
4-3
4-4
4-5
4-5
5 -1
5 -1
5-1
5 -3
5 -3
5 -4
5 -4
5 -5
5 -6
5 -6
6-1
6-1
6- 2
6- 2
6-3
6-3
6-3
7 -1
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EM
1110-2-3006
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1994
Sub ject aragraph
ag e
Relays
-2-3
Controlan dMetering
Equipment
-3-3
Load/DistributionCenters
-4
-3
Estimated
Station
Service
Load
-5
-3
Chapter
8
ControlSystem
General
-1
-1
ControlEquipment-2
-1
TurbineGovernor -3
-2
Large
Power
Plant
Control
-4
-2
SmallPower
Plant
Control
-5
-4
Protective
Relays
-6
-4
AutomaticGeneration
Control-7
-6
Chapter
9
Annunciat ion
System
General -1
-1
Audio
an d
VisualSignals
-2
-1
Annunciator
-3
-1
SequentialEvents
Recorder
-4
-2
TroubleAnnunciatorPoints
-5
-2
Chapter
10
Communicat ion
System
General
0-1
0-1
VoiceCommunicationSystem
0-2
0-1
Dedicated
CommunicationsSystem 0-3
0-1
Communication
System
Selection
...
0-4
0-4
Chapter
1 1
Direct-Current
System
General 1-1
1-1
Batteries 1- 2
1-1
Battery-Charging
Equipment
1-3
1-2
Inverter
Sets
1- 4
1-2
BatterySwitchboard
1-51-2
Chapter
12
Lighting
an d
ReceptacleSystems
Design 2-1
2-1
IlluminationRequirements
2-2
2-1
Efficiency
2-32-2
Conductor
Types
an d
Sizes
2- 4
2-2
Emergency
Light
Control
2-5
2-2
ControlRoom
Lighting
2- 6
2-3
Hazardous
AreaLighting
2- 7
2-3
Receptacles
12-8
2-3
Subject aragraph
Chapter
13
GroundingSystems
General
3-1
Safety
Hazards
3- 2
FieldExploration3-3
GroundMats
3- 4
PowerhouseGrounding
3-5
Switchyard
Grounding
3-6
GroundingDevices
3-7
Chapter
14
Conduit
an d
TraySystems
General
14-1
Condui t 14-2
Cable
Trays 14-3
Chapter
15
Wire
an d
Cable
General
5 -1
CableSize
5 -2
Cable
System
Classification
5 -3
Condui t
an d
CableSchedules 5 -4
Chapter
16
Procedure
fo r
Powerhouse
Design
Design
Initiation
16-1
DesignProcess
16-2
Chapter
17
Genera l
Design
Memorandum
Requirements
17-1
Page
13-1
13-1
13-1
13-1
13-2
13-3
13-3
14-1
14-1
14-2
15-1
15-1
15-1
15-2
16-1
16-1
17-1
Chapter
18
Feature
Design
Memorandums
an d
Drawings
Design
Memorandum
Topicsan dCoverage
8- 1
18-1
FeatureDesign
Memorandums
8-2
18-1
Engineering
Documentation
8-3
18-1
Design
Drawings8- 4
18-1
Chapter
19
Construction
Specifications
an d
Drawings
Specifications
19-19- 1
ConstructionDrawings
19-2
9- 1
Chapter20
Analysis
ofDesign
Permanent
Record 20-1
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E M
1110-2-3006
30J u n1 994
Sub ject
Paragraph Page
Up-To-Date
Values
...
20-2 20-1
Expansion
20-3
20-1
Appendix
A
References
A -l
AppendixB
PowerTransformer
Studies
an dCalculations
B -l
III
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Chapter1
Introduction
1-1.
urpose
This
manual
rovides
uidance
ndssistanceo esign
engineers
inthe
development
of
electrical
designs
fo r
new
hydroelectric
ower
plants.hemanual
hould e se d
whenpreparing
lectrical
esignsorhydroelectricpower
plants
or ivil
worksacilitiesbuilt,
wned,
r
perated
by
heCorps fEngineers.
reatment
f
electricalys-
temsor umped
torage
lants
s
ot
overed
n
he
manual,although
much
of
theinformationis
applicable
to
pumped
storage
plant
systems
an dsubsystems.
1-2.
pplicability
This
manual
is
applicabletoal l
civil
worksactivitieshav-
in g
esponsibilities
orthe esign
of
hydroelectric
ower
plants.
1-3.
eferences
Required
nd
elated
ublications
re
isted
n
Appendix
A.
1-4.cope
a .enerator
rating.he
manual
presents
good
engi-
neering
practice
in
designingelectricalsystemsfo rhydro-
electric
power
plants
employing
generating
units
of
up
o
approximately30 0MW
in
rating.
b .lant features.hemanual ealswiththeelectri-
ca l
features
fhydroelectricpowerplants,
ndcovers
the
generating
quipment,tationervice, ariouswitchyard
an dransmissionin errangements,etails
f
ighting,
communication
nd
ontrol,
ndrotective
evices
or
plant
quipmentnd
elated
uxiliaries.eneratorsnd
powerransformersre
reated
nder
heir
espective
headings,but
therequipment,
materials,nddevices
re
discussed
nder
he
istinctunctionalystems
n
which
they
ar e
used.
c .
pecification
preparation.
nformation
is
presented
to
acilitate
he
reparation
f
pecifications
or
major
items
of
equipmentusingpertinentapprovedguide
peci-
fications,nd
pecifications
or
uggestedlant
esign
features
which
take
intoconsiderationthenumerousancil-
lary
nd
ontrol etails
that
ar e
required
to
arry
ut
the
intended
lantunction.
herelternateesigns
f
functionalystemsreiscussed,
referred
esigns
EM
1110-2-3006
30
Ju n
94
indicated
o
ecure
egree
ofuniformity
n
lants
of
similar
size
an dcharacter.
hese
preferred
designs
should
beollowedunlessunusualonditionsmakethemunsuit-
able
or
unreasonably
expensive.
1-5.
odes
Portions
f
he
odes,
tandards,
r
equirementsub-
lished
y
he
ssociationsr
gencies
isted
elow
re
applicable
o
heork.
omplete
isting
fodes,
standards,nduides
sontained
n
ppendix,
References.
Institutef
lectrical
ndlectronicsngineers
(IEEE)
American
National
Standards
Institute
(ANSI)
Electric
Power
Research
Institute
(EPRI)
Illuminating
Engineering
Society
(IES)
National Electrical Manufacturers Association
(NEMA)
NationalFireProtection
Association(NFPA)
Underwriters
Laboratory
(UL)
1-6.
riteria
a .
referred
methods.
hedesign
methods,assump-
tions,
lectrical
haracteristics
riteria,
etails,
nd
ther
provisionsoveredn
hi s
anualhouldeollowed
whereverpracticable.hemanualw as
repared
orus e
byengineerswith
basic
knowledge
o f
theprofession,
nd
judgmentnd iscretionhould e se d
n
pplyinghe
materialcontained
herein.
n
cases
wherepreferred
alter-
natives
ar e
notdentified,
esigners
hould
follow
recom-
mendations
ontained
n
he
eferencematerialsisted
n
the
Bibliographythat
apply
to
the
work
to
beperformed.
b .
eviations
from
preferred
methods.
epartures
from
hese
uidesmay e
ecessary
n
ome
ases
n
order
o
meet
pecial
equirements
r
onditions
of
the
work
underconsideration.
he n
lternatemethods,
pro-
cedures,
nd
ypesf
quipmentre
nvestigated,
inal
selection
hould
ot
e
ad e
olely
n
irst
ost,
ut
shouldeasednbtainingverall
conomy
nd
security
y
iving
ppropriate
eight
o
eliability
f
service,
as e
cost) f
maintenance,
nd
ability
to
restore
service
ithin
hort
im envent
famage
r
abnormal
i rcumstances. Whether
rchitect-engineers r
1 - 1
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EM
1110-2-3006
30Ju n94
Hydroelectric
Design
Centerpersonnel esignhe ower
plant,
he
riteria
nd
nstructions
et
ut
in
Appendix
A
of
Guide
Specification
CE-4000
shouldbefollowed.
1-7.ydroelectric
DesignCenter
(HDC)
Theengineering
of
hydroelectric
projects
is
highly
spe-
cialized
ield,articularly
hengineering
esign
nd
engineering
upport
of
operational
ctivities.
norder
to
assistield
perating
ctivitiesFOA),heorpsf
Engineersha sestablishedthe
Hydroelectric
DesignCenter
(HDC)
she
enter
of
expertise
nhe orps
of
Engi-
neers
or
hi sork.
he
O A
il letainomplete
responsibility
an d
uthorityfo rthe
work,
ncluding
fund-
ing,
nspection,esting,ontractanagement,nd
administration.
he
DCil l
erform
he
ollowing
engineeringanddesign
services:
a.
rovide
he
echnical
ortions
f
econnaissance
reports
an d
other
pre-authorization
studies
fo r
inclusion
by
the
requesting
FO A
intheoveral lreport.
b .
rovidehe rchitectural,tructural, lectrical,
nd
mechanical
esign
or
he
owerhouse
ncluding
witch-
yards,relatedfacilities,an dal lhydraulictransient
studies.
c.
repare
preliminary
design
reports
an dtheeature
designmemorandums
or ydroelectric
ower
lantsor
the
requestingFOA.
d.
repare
lans
nd
pecifications
or
upply
nd
construction
ontracts
nd
upplemental
major
equipment
testing
contracts.
e.rovidetechnicalreview
of
shop
drawings.
/
rovide
echnical
ssistance
o
he
ontracting
Officer'sepresentativetmodelndieldests.
he
H DCwillanalyze
results
an d
make
recommendations.
g.
ssist
n
reparation
fOperationnd
Mainte-
nance
Manua ls .
h.
rovide
necessaryengineeringan dcomputer-aided
drafting
CAD)
ork
o
ncorporate
as-buil t hanges
intothe
electronically
readable
record
drawingfiles,
an d
assure
complete
coordinationfo rsuchchanges.
i .
articipateneview
of
plans
nd
pecifications
fo r
on-Federal
evelopment
tCorpsof
Engineers
ro -
jects
in
accordancewith
ER
1110-2-103.
1- 2
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Chapter2
Basic
SwitchingProvisions
2-1.
ne-L ine
Diagrams
a.
eneral.
he evelopment
of
a
lant
lectrical
one-line
iagram
hould e
ne
ofthe
irst
asks
n
he
preliminarydesign
of
theplant.
n
evaluatinga
plant
fo r
good
electricalsystemdesign,
itis
easy
to
discuss
system
designinterms
of
theplant'sone-lineelectrical iagram.
The
elationship
etween enerators,
ransformers,rans-
mission
ines,ndources
of
tationervice owerre
established,
longwiththeelectrical
ocation
ofthesso-
ciatedpowercircuit
breakers
an dtheircontrol
an dprotec-
tionunctions.heevelopmentof
he
lantne-line
diagram
an dthe
switchingarrangement
required
to
imple-
ment
theone-line
ma yhelpdetermine
theratingofgener-
ators
nd
onsequently
the
ating
of
the
urbines
nd
the
size
f
heowerhouse.
neveloping
lant
ne-line
diagram
lternatives,
sehouldbemade
of
IEEE
C37.2
to
ai dthose
reviewing
the
alternatives.
b .valuation
factors.
omeactors
o
onsider
n
evaluating
ne-line
iagrams
nd
witching
rrangements
include
whether
he
lant
will
e
manned
runmanned,
equipmentreliability,
whether
the
plant
willbe
used
in
a
peaking versus
a
baseloadmode
of
operation,the
need
to
maintain
minimum
lo w
as t
he
lant,
r
whether
there
is
a
restriction
on
therateofchange
of
flow
past
the
plant.he
as eoa dmodemplies imitednumber
of
unit
tart-stop
perations,
nd
ewer
reaker
perations
than
would
be
required
fo r
peaking
operation.
nmanned
operationndicates ee dor
eliablerotection
nd
control,
nd
implicityofoperation.ftherereevere
flow
estrictions,
oupled
ith
ee d
or
ontinuous
reliable
power
output,
it
ma y
be
necessary
toconsider
the
unit
rrangementcheme ecauset
provides
themini-
mu m
oss
f
eneration
uring
irstontingency
disturbances.
c.esignharacteristics.
n
eneral, ood
lant
electricalne-linehouldbe evelopedwiththe
oal
of
achievingthe
fol lowingplantcharacteristics:
(1 )
afety
an d
reliability.
(2 )
implicityof
operation.
(3 )ood
technical
performance.
EM
1110-2-3006
30
Ju n
94
(4)
eadilyaintainable
e.g.,riticalomponents
ca n
e
emoved
ro m
ervicewithouthutting
ow n
he
balance
of
plant).
(5 )lexibility
to
dealwithcontingencies.
(6 )
bility
to
accommodatesystemchanges.
2-2 .lantScope
a.xtentofproject.
he n
onsidering
witching
schemes,
here
rewo asic
ower
lant evelopment
scopes.ither
theproject
copewillnclude transmis-
sion-voltageswitchyardassociated
with
the
plant
or , lec-
trically,
the
project
scope
ends
at
the
line
terminals
of
the
high-voltagedisconnectswitchisolatingtheplantfromthe
transmission
ine.
requently,
heorpsf
ngineers
project
scopelimitisthe
latter
situation
with
theintercon-
necting
switchyard
designed,
constructed,
an d
operated
by
the ederal
ower
Marketing
Agency
PMA),
wielding
the ower
r
y
he ublic tility
purchasing
he owe r
through
thePMA.
b .edium-voltagequipment.
hether
r
not
he
scope
ncludes
witchyard,
he
ne-line
evelopment
willnvolvehewitchingrrangement
of
the nits,he
number
of
units
nhe
enerator
tep-up
G S U )
rans-
formerank,ndhe
rrangement
of
powerquipment
from
he
enerator
o
he
ow
oltage
erminals
ofhe
G SUransformer.hi s
quipment
s
edium-voltage
(0.6
kv-\5kV )lectricalquipment.hishapter
describes
election
f
ppropriate
witching
chemes,
including
evelopment
f
quipment
atings,
conomic
factors,ndoperationalonsiderations.
hapter6,
Gen-
erator
Voltageystem,
escribesquipment
ypes
nd
application
considerations
in
selecting
the
medium-voltage
equipmentused
in
theseystems.witchingschemes
fo r
generating
nitsndransformers
ma y e
of
ither
he
indoororoutdoortype,
or
a
combination
ofboth.
c.
igh-voltageequipment .he n
development
does
include witchyard
r
ubstation,heam eonsidera-
tionspply
in
developingthe eneratorvoltagewitching
schemes
describedinparagraph
2-2b.ombined
develop-
mentdoesprovidethe
opportunity
to
applycostan dtech-
nical
rade-offs
etween
he
medium-voltage
ystems
of
theower
lant
ndheigh-voltage
ystemsfhe
switchyard.
hapter5 ,High-VoltageSystem, describes
switchyard
rrangements,
quipmentan dpplication
on-
siderationsn evelopinghewitchyard
ortion
fhe
2-1
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E M1110-2-3006
30
J u n94
one-l inediagram.
witchyards
ar e
predominately
outdoor
installationsl thoughnpecialases
e.g.,
n
underground
owe r
lant)igh-voltage
F
6
nsulated
equipmentsystems
ma y
finduse.
2-3.
n it
Switching
Arrangements
a .Unit rrangement.
unit
chemehowing
outdoor
witching
of
the enerator
nd
ransformerbank
as
unit
on
thehigh-voltage
id e nly,s
hown
in
Fig-
ure
2-la.heunitcheme
s
well-suited
to
mallpower
systems
here
ossfarge
locks
f
eneration
re
difficult
oolerate.
heossofa
ransformer
ank
r
transmission
in e
n
ll
ther
rrangementswouldmean
the
oss
f
more
ha n
ingle
eneration
nit.
mall
powersystemsar esystems
no t
able
to
compensatefo rthe
loss
of
multiple
units,
as
could
occur
usingother
arrange-
ments.heunit cheme
makes
maintenance utages
simpler
to
arrange
an d
is
advantageous
where
the
plant
is
located
ea r
he igh-voltageubstationmaking hort
transmission
istance.
hischeme,
with
ransformer
an d
transmission
line
oreachgeneratorunit,tends
to
e
I
.ni t
rl
u u u
[el
Gj
G)
e.enerator
bu s
d.aired
on
Ifhighside
e .
Tw o uni ts
on
three-
wirtdinfltransformer
f.
ou r
unitsontires-
windingtransformer
Figure2-1.ain
unitswitchingschemes
higherinfirstcost
than
schemes
that
have
multiple
gener-
atorsn ingleransformer
ndransmissionine.
Medium-voltage
quipment
or
the
nit
ystems
ncludes
busleadsfrom
thegenerator
to
the
G SUtransformeran d
isolation
disconnects
fo r
maintenance
purposes.
b .
Multipleunitarrangements.
(1 )narger
owerystems,here
os sf
arger
blocksof
generationma y
betolerable
rwhere
the
plant
isinterconnected to
an
EHV
grid
(345
kV an dabove),
tw o
or
ore
enerators
ogetherithheirransformeror
transformer
ank)
ma y
e
onnected
o
ne
witchyard
position.ome
of
theommonly se dchemesre
is -
cussed
nhe
ollowingparagraphs.efer
to
Chapter
,
Generators
fo rdiscussiononthe
protection
requirements
fo rgeneratorarrangements.
(2 )woenerators
ay
e
onnectedowo-
winding
ransformer
an k
hrough
Medium-Voltage
Cir-
cuit
Breakers
MVCBs)shown n igure2-lb.
hi s
arrangement
ha s
the
advantage
of
requiring
a
single
trans-
mission
in e
or
tw o
units,
ather
ha nthe
woinesha t
would
e
equired
or
unit rrangement.his
ro -
vides
lear
avingsnin e
ight-of-way
ost
nd
maintenance.singletransformer,eventhough
of
higher
rating,s lsoes s
ostly
ha nhewo
ransformers
ha t
wouldbe eededor
unit
ystem.
gain,
he
pace
requirement
s
ls o
es sthanortw oeparateransform-
ers.herererade-offs:
n
M V C B
or
each
enerator
is
needed,
the
generator
groundingan dprotectionscheme
becomes
moreomplex,nddditionalpacendquip-
ment
ar e
needed
fo r
the
generator
medium-voltage
(delta)
bus.
nconomictudyhould emade
o
justifyhe
choice
ofdesign,
nd
the
ransformerimpedancerequire-
mentsshouldbeevaluatedifthe
power
systemiscapable
of
delivering
alarge
ontribution
toaultsnthegenera-
to r
side
of
thetransformer.
(3 )
or
mall
enerating
lants,
cheme
which
connects
the
eneratorsthroughM V C B s
ohe
enerator
busshownn igure -lc.ne rmore
GS U
rans-
formers
ca n
beconnected
to
the
bus(one
is
shown),
with
or
ithout
ircuitreakers;
owever,se
f
multiple
transformers,ac hwithits
wncircuit
breaker,
esults
n
a
er y
lexible peratingrrangement.ndividual
rans-
formers
ca n
be
taken
ou t
of
service
fo r
testing
or
mainte-
nancewithout
taking
thewhole
plant
outofservice.
he
impedances
of
the
transformers
must
be
matched
to
avoid
circulating
urrents.s
oted
bove,he
rotection
scheme ecomes
more
omplex,
u t
hishould eon-
sidered
long
with
he
ther
rade-offswhen
omparing
this
schemewiththe
other
plant
arrangementspossible.
2-2
-
8/11/2019 Centrale Hidro
11/118
(4)wo
roreenerators
an
e
onnected
o
individualransformer ankshrough
eneratorM V C B s
with
he
ransformers
used
hrough
isconnectwitches
onhe igh-voltage
id e
s
hownnFigure -Id .his
arrangement as
ome
f
he
dvantages
f
he
unit
system
shown
in
Figure
2-la,
nd
discussed
above,
long
with
he
dvantage
f
ewerransmission
ines,
hich
results
n
less
right-of-way
needs.
heresomeoss
of
operationallexibility,ince
ransmission
in e
ervice
requires
aking
ll
of
the
nits
utofservice,nd in e
fault
will
esult
inuddenossofa
ratherlarge
block
of
power.gain,
eeds
ofthe
ulk
power
distributionys -
tem
ndheconomics
f
herrangementuste
considered.
(5 )w o rmore enerators
ma y
e
onnected
o
three-windingransformer an k
s
hown
n
igure
2-le
an d
.he enerators
would
eonnected
o
hewo
low-voltage
windings
hrough
enerator
MVC B s .
his
arrangement
l lows
pecification
f
owalue
f
through
impedance
thus
increasing
the
stability
limits
of
the
ysteman dal lowingthespecification
of
a
highvalue
of
mpedance
etween
hewo
ow-voltage
G SUrans-
former
windings.
hiseduces
he
nterrupting
apacity
requirements
of
the
enerator
reakers.hischemes
particularly
dvisablewhenhe
lant
s
onnected
o
bulkpower
distribution
systemcapableofdelivering
high
fault
currents.gain,
transformeror
line
faults
willresult
in
the
potential
loss
to
the
bulk
powerdistributionsystem
of
elatively
arge
lock
of
eneration.ransformer
maintenanceor
testing
needswill
requireoss
ofthe
gen-
eratingapacity
of
al l
ourunits
or
he
uration
of
the
test
or
maintenance
outage.
his
scheme
finds
application
where
plants
ar e
interconnected
directly
toan
EH V
grid.
2-4.
ubstationArrangements
a.
eneral.
igh-voltage
ubstationrrangements
an dapplicationconsiderationsar edescribed
in
Chapter5 ,
High-Voltageystem. igh-voltage
ystems
nclude
those
ystemsrated
9
kVan dbove.he
lant
switch-
ing
rrangementhould
e
oordinated
with
he
witch-
yard
rrangement
onsure
ha t
he
esulting
ntegration
achievesthe
design
goals utlined
in
paragraph
2-lc
in
a
cost-effectivemanner.
b .
ubstationswitching.
ome
plantsma y
be
electri-
cally
ocated
nhe owerystemo
heir
ransmission
line-voltage
uses
ecome
onnecting
in k
or
wo r
more
linesinthepower
system
network.
hi s
ca n
require
an
ppreciablemount
ofhigh-voltagewitching
quip-
ment.
he
desirability
of
switching
small
units
at
genera-
to r
oltage
hould
evertheless
envestigatednuch
E M
1110-2-3006
30J u n
94
cases.
hapters,High-Voltage
ystem
nd
,
Generator-Voltage
ystem, iscusswitching
nd
us
arrangements
in
more
detail.
2-5.
aultCurrentCalculations
a .
eneral.
ault
urrent
alculations,
sing
he
methodofymmetricalomponents,hould
e
repared
fo reachone-linechemeevaluated
to
eterminerequired
transformer
impedances, eneratorndtation
witchgear
breaker
nterruptingatings,
ndatings
f
isconnect
switchesan dswitchyardcomponents.
onventionalmeth-
ods
of
making
the
necessary
fault
current
calculationsan d
of etermininghe
equired
atings
or
quipment
re
discussed
n
EEE
42
nd 99.umberofsoftware
programs
ar e
commercially
availablefo rperforming
these
studies n
personal
omputer.w oofthese
programs
are:ETAP,ro mOperationTechnology,Inc., 7870
ky-
park
Circle,
uite
02 ,
rvine,
CA
2714;
nd
DAPPER
an d
-FAULT,
ro m
K M
ystems
nalysis,
nc.,
225SSepulvedalvd,
uite
5 0,
anhattaneach,
CA90266.
b .riteria.
he
ollowing
riteriahould eol -
lowed
n
eterminingalues
f
ystem
hort-circuit
capacity,ower
ransformer
mpedances,nd
enerator
reactances
to
be
usedinthefaultcurrentcalculations.
(1 )
ystemhort-circuitapacity.hisshe
estimated
aximum
ltimateymmetricalVA
hort-
circuit
apacity
available t
the
igh-voltage
erminals
of
the
S U
ransformer
onnected
o
heenerator nder
consideration,
or
external
to
the
generator
under
consider-
ation
fnotep-up
ransformer
s
sed.
t
ncludes
he
short-circuit
capacity
available
from
al l
othergenerators
in
the
powerplant
in
addition
to
the
short-circuitcapacity
of
the
igh-voltageransmissionystem.ystemhort-
circuit
apacity
s
sual ly
eadily
vailable
ro m
ystem
planners
of
the
utility
orthe
PM A
to
whichthe
plant
will
beconnected.
(2 )
alculating
ystem
hort-circuit
apacity.he
transmissionystemhort-circuitapacity
an
ls o
e
calculated
with
reasonableaccuracy
whensufficient
infor-
mation
regarding
the
planned
ultimate
transmission
system
isvailable,
ncluding
he
otal enerating
apacity
on -
nectedoheystemndhempedancesofthe arious
transmissioninesha t
rovide athro m
he
nergy
sourcestotheplant.
(3 )
stimating
ower
ystem
ault
ontribution.
Whendequatenformation
egarding
he
ransmission
system
s
navailable,
stimating
methods
must
be
sed.
2-3
-
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EM
1110-2-3006
30Ju n94
In
llases,heystem
hort-circuit
apacityoruse
n
theaulturrentalculations
hould
estimated n
conservative
asis,
.e.,
hestimatehoulde
arge
enough
to
llowfo ratleast
a
0-percentmargin
of
error
inthe
ystem
ontribution.
hishouldprovide actor
of
safety,
an d
also
allow
fo r
addition
of
transmission
lines
an d
generation
apacitynotpresentlyplannedor
contem-
platedbysystemengineers
an d
planners.nly
in
excep-
tional
cases,such
as
small-capacity
generating
plants
with
only
one
ortw oconnecting
transmission
lines,houldthe
estimatedultimate
ystem
hort-circuitry
apacity
e
es s
than
1,000MVA.
(4)
Power
transformerimpedances.
(a )ctual
es t
aluesfowe r
ransformer
impedanceshould
e
se d
n
heault
alculations,f
theyar eavailable.
f
test
valuesar eno t
available,design
values
of
impedance,
djusted
or
maximum
EEE
tan-
dard
minus
olerance
7 .5
ercent
or
two-winding
rans-
formers,nd0
ercent
or
hree-windingransformers
an d
uto-transformers)hould
e
sed.
ominal esign
impedance aluesreontained
n
able -1fChap-
te r
4,
Power
Transformers.
or
example,fthe
imped-
ancef wo-winding
ransformer
s
pecified
o
e
8 .0
percent,
ubject
oEEEolerances,
he
ransformer
will e esignedor .0
ercent
mpedance.owever,
the
es t
mpedance
may
e
sows .0
ercent
es s
7.5-percent
tolerance,or7 .4percent,
an d
thislower
value
shouldbe se d
n
thealculations,incetheowervalue
of
impedancegivesgreaterfaultcurrent.
(b )
f
he
mpedance
f
he
bove
xample
rans-
former
s
pecified
o e
o t
moreha n
.0
ercent,he
transformer
will
be
esigned
fo r
7.44
ercent
impedance,
so
thatthe
upper
impedancevaluecouldbe
7.998
percent,
an dheower
mpedance
alue
dueohe
esign
oler-
ance)could
be
as
lo was
6.88
percent,which
is
7.44per-
cent
less
the
.5
ercenttolerance,
which
hould
be
used
inthe
calculations
because
the
lower
value
gives
a
higher
fault
current.
sing
the
lower
impedance
value
is
a
more
conservative
ethod
f
stimating
he
ault
urrent,
becausetnticipates
worst
ase ondition.mped-
ances
or
hree-winding
ransformers
nd
uto-transform-
er s
hould
ls oe
djusted
or
tandard
olerance
n
accordancewiththeboveriteria.hedjustedimped-
ance
shouldthenbeconverted
to
an
equivalent
impedance
fo ruse
n
theequencenetworks
n
theaulturrentcal-
culations.ethods
of
calculating
he
quivalentmped-
ancesnd evelopingquivalent ircuits re escribed
n
IEEE242.
(5 )enerator
eactances.ctuales taluesf
generator
eactances
hould
ls o
e
se d
n
he
alcula-
tions
if
they
ar e
available.f
testvalues
ar e
not
available,
calculated
values
of
reactances,obtainedfrom
the
genera-
to r
manufacturer
nddjusted
o
heppropriateM V A
base,
hould
be
used.
ated-voltage(saturated)values
of
theirect-axisransienteactanceX'
d
),
he
irect-axis
subtransienteactance
X
d
),nd
he
egative-sequence
reactanceX
2
),ndtheero-sequenceeactanceX
0
),
re
the
fourgenerator
reactancesrequiredfo r
us e
n
thefault
currentcalculations.fdataar e
not
available,Figure
3- 2
in
hapter
,
Generators, rovides
ypicalalues
f
rated-voltage irect-axisubtransientreactance
orwater-
wheel
enerators
ased
nachine
ize
nd
peed.
Designreactance
aluesre
nterrelated
with
ther
speci-
fied
machine
values
(e.g.,
short-circuit
ratio,
efficiency)
so
revised
atahould e
ncorporated
ntoaultomputa-
tionsonceamachineha sbeenselected.
2-4
-
8/11/2019 Centrale Hidro
13/118
E M
1110-2-3006
30
J un
94
Chapter
3
Generators
3-1.
eneral
a.
esignonstraints.
lmost
ll
fhe
ydraulic-
turbine-driven
generators
used
in
Corps 'powerhouses
will
beynchronous
lternating-current
machines,which ro -
duce
lectricalnergyby
hetransformation
of
hydraulic
energy.
helectrical
nd
mechanical
esign
f
ac h
generator
must
onformohe lectricalequirementsof
the
ower
istribution
ystemo
which
twill
e
on-
nected,
nd
ls o
o
he
ydraulic
equirements
f
ts
specific lant.eneral orpsof
Engineers
waterwheel
generator
design
practice
is
covered
by
the
Guide
Specifi-
cationCW-16210.
b .
esign
haracteristics.
ince
waterwheel
enera-
tors reustom
esigned
o
match
he
ydraulic
urbine
prime
mover,many
ofthe
eneratorcharacteristics
e.g.,
short-circuit
ratio,
eactances)
anbe
aried
over
afairly
wide
ange,
epending
n
esignlimitations,
o
ui t
pe -
cificlant
equirements
nd
ower
istribution
ystem
stability
eeds.
eviations
ro mhe
ominal
enerator
designparametersca nhave
a
significanteffect
on
cost,
so
aareful
valuation
ofpecialeatureshould emade
an d nly
se d
n
he
esign
f
heir
ee dustifies
he
increased
cost .
3-2.lectricalCharacteristics
a.
apacity
and
powerfactor.
eneratorcapacity
is
commonly
expressed
in
kilovolt-amperes
(kVA),
ata
given
( rated ) ower
actor.
he
oweractor
he
enerator
will
be
designed
fo r
is
determined
from
a
consideration
of
the
lectrical
equirements
ofthe ower
istribution
ys -
tem
itwillbe
connectedto .
heserequirements
include
a
consideration
of
the
nticipated
oad,he lectricaloca-
tion
of
the
plant
relative
to
thepower
system
load
centers,
an dhe
ransmission
ines,
ubstations,
ndistribution
facilities
involved.
Seeparagraph
3-2/).
b .enerator
o w e rutput
ating.
he
ilowatt
rating
f
he
enerator
hould eompatible
ithhe
horsepower
ating
f
he
urbine.
he
ost
ommon
turbineypesrerancis,
ixedladeropeller,
nd
adjustable lade
ropeller
(Kaplan).ee etailed iscus-
sion
on
turbine
types
an d
their
selection
an d
application
in
EM
110-2-4205.
ac h
turbine
typeha sdifferent
operat-
in g
characteristics
an d
imposes
a
different
se tof
generator
designriteriao
orrectly
atch
he
enerator
o
he
turbine.
Fo r
ny
urbineype,
owever,
he
enerator
should av eufficient
ontinuous
apacity
o
andlehe
maximum
orsepowervailablero m
he
urbine
t
100-percent
gatewithout
the
generatorexceeding
its
rated
nameplateemperature
ise.
n
etermining
enerator
capacity,ny
possibleuturehanges
tothe
project,uch
as
raising
the
orebay
level
nd
ncreasing
turbine
utput
capability,hould eonsidered.
igure
-1
hows
typical
capability
curve
fo r
a
hydroelectric
generator.
-LMTEO
Y
I EL D
EATING
R A T E D
VA
L IM IT ED
BY
TATOREAT INC
SYSTEM
TABUTY
llitT
Figure
3-1.
ypical
hydro-generator
capability
curve
c.
eneratoroltage.he oltage
of
large,
low-
speed
eneratorshould
e
s
ig h
s
heconomy
of
machine
esign
ndhe
vailability
ofswitchingquip-
ment
ermits.enerators
with
oltage
atingsn
xcess
of
6.5
V
av e
ee nurnished,utxceptn
pecial
cases,
manufacturingpractices
enerally
ictate
nupper
voltage
imitf
3.8
kV
or
achines
p
hrough
25 0
MV Aating.
asedon
requiredgenerator
reactances,
size,ndWk
,lower
generator
voltage,uchas .9V,
ma y
e
ecessary
r
rove
o
emoreconomical
ha n
higher
voltages.
f
the
enerators
reoervenstab-
lished
istribution
ystem
t
enerator oltage,
he n
he
system oltagewillnfluenceheelection
of
generator
voltage,
nd
ma y
dictate
theselection
an darrangement
of
generatorleads
lso.
eneratorsofless
ha n
,000VA
should referably
e
esignedor
80
V ,
,400,
r
4,160V,dependingonthefacilities
connecting
thegener-
ator
to
itsload.
3-1
-
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14/118
EM
1110-2-3006
30
J u n94
d .
Insulation.
(1 )he
generator
stator
winding
is
normallysupplied
with
ither
ClassB rClass
nsulation
materials,
with
the
nsulation
ystemmeetingheemperatureimitsnd
parameters
f
AN SI
50.12
e.g.,
5
C
is e
bove
40Cmbient).
hehoiceofinsulationystemypes
dependsn
achineize,ow
heachine
il l
e
operated,nd esiredwinding
ife.
odern
ydro nits
ar esubjected
to
awidevariety
of
operatingconditionsbut
specifications
hould
e
reparedith
hententf
achieving
winding
ife
xpectancyof35
r
more
ears
under
anticipated
operating
conditions.
(2 )he
choice
between
Class
B
or
ClassF
insulation
systemsorhetatorindingil lependnhe
expected
us e
of
thegenerator.f
it
will
be
operated
con-
tinuously
at
rnear
rated
load, r
ha s high
probability
of
operating
verloaded
or
onger
ha n
r
t
ime,
thenhe
Class nsulation
ystem
hould
epecified.
For
generatorsthatca n
be
expected
tobeoperated
below
rated
oad
most
of
the
ime,ndt
r
nearfulload
or
onlyimited eriods, Class
nsulation
ystemwould
be
atisfactory.nnsulationystem sing
olyester
resin
as
abinder
should
be
onsidered
a
Class
Bystem,
sincethesofteningtemperature
of
polyesterresin
is lose
to
the
Class
F
temperature
limit.
(3 )tator
inding
nsulation
ystems
onsist
f
groundwallnsulation,
usually
mica,withasuitablensu-
lation
binder,general ly
a
thermosetting
epoxy
or
polyester
material.hese
hermosetting
ystemschieve ielectric
strengths
quivalent
to
that
of
older
thermoplastic
nsula-
tion
ystemswith
es s
hickness
ha nhe
lder
ystems,
al lowing
he
seof
additional
opper
n
iven
tator
slot,
chieving
etter
ea t
ransfer,
ndpermittingooler
operation.
hermosetting
nsulationystemsolerate
higher
ontinuous
perating
emperatures
ha n
lder
ys -
temswithlessmechanical
deterioration.
(4)olyester
resin
ha s
ower
ofteningtemperature
(known
s
he lass
ransition
emperature,
g
)
ha n
he
more
ommonlyavailablepoxyinsulation
ystem,
ut
it
ha stheadvantage
of
beingslightly
moreflexible
thanthe
epoxy
ystem.
his
light
lexibility
sn
dvantage
whennstalling
multi-turn
oils
n
tator
lots
nmall
diameter
generators.
heplane
of theoil
side
coincides
withthe
plane
oftheslotoncethecoi lisinstalled.ur -
in g
installation,
however,
the
coi lside
approaches
theslot
at
a
slight
angle
so
that
the
coi lmust
beslightly
distorted
to
maketheside
enter
the
slot.
olyester
is
less
likely
to
fracture
ha n
poxy
he n
istorted
uringnstallation.
Polyester
as
o
dvantageover
poxy
fhestator
winding
s
f
he
oebel
ar
ype.poxy
s
sually
preferred
becauseofits
higher
T
g
,
an d
the
polyester
insu-
lationsystem
ma y
notbeavailableinthefuture.
(5 )hermosettingnsulationystem
aterialsre
hard
an d
do
not
readily
conform
to
the
stator
slot
surface,
sopecialechniquesndareful
nstallation
rocedures
must e
se d
n
pplying
hesematerials.orps uide
specification W-16210 rovides
uidance
nypes
f
windingndoil
abrication
echniques,ndnstallation,
acceptance,
ndmaintenancerocedures
o
ese d
o
ensurelong,trouble-free
winding
life.
e .
Short-circuit
ratio.
(1 )hehort-circuitratio
ofagenerator
is
the
ratio
of
the
ieldcurrent
required
to
produceratedopencircuit
voltage,oheield
urrent
equired
o
roduce
ated
stator
urrent
he n
he
enerator
utput
erminals
re
short-circuited.
he
short-circuit
ratioisalso
the
recipro-
ca l
f
the
er
nit
alue
f
heaturatedynchronous
reactance.he
short-circuit
ratio
ofa
generator
is
amea-
sure
of
thetransientstability
of
theunit,
with
higher
ratios
providinggreaterstability.able3-1istsnominalshort-
circuit
atios
or
enerators.
hort-circuit
atios
igher
than
ominal
alues
an
e
btained
ithoutuch
increaseinmachineize,
u t
largevaluesof
short-circuit
ratio
mustbe
obtainedbytrade-offs
inotherparameters
of
generator
erformance.
ncreasing
he
hort-circuit
atio
aboveominalalues
ncreaseshe
enerator
os tnd
decreases
he
fficiencynd
heransient
eactance.
Included
n
Table3-1rexpectedpricedditions
to
he
generator
asic
ost
nd
eductions
n
fficiency
nd
transientreactancewhenhigher
than
nominalshort-circuit
ratio
values
ar e
required.
(2 )
ngeneral ,
he
requirementfo rotherthannomi-
nal
hort-circuitatios
an
e
eterminednl yro m
stabilitystudyoftheystemonwhichthe
generator
isto
operate.
f
the
stability
study
showsthat
generators
at
the
electricalocationofthe
lant
n
he owerystemre
likely
o
xperience
nstability roblems
uring
ystem
disturbances,
then
highershort-circuit
ratio
values
ma y
be
determinedro mhemodeltudiesndpecified.fthe
powerplant
esign
s
ompletednd
the
enerators
ur-
chased rior
o
eterminationof
hexteriorystem
connections
nd
their
haracteristics,
.e.,
efore
the
on-
necting
ransmission
ines
re
esigned
rbuilt,
hi swill
precludemaking ystemtudy
o
ccurately
etermine
the
short-circuit
ratio
required.
here
itis
not
feasible
to
determinehehort-circuit
atio
ndhere
re o
actors
indicating
ha t
igher
ha nominal
alues
re
eeded,
then
nominal
short-circuitratios
shouldbe
specified.
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Table
3-1
Genera tor
Short-Circuit
Ratios
Short-CircuitRatios
0.8PF
at
0.9PF
0.95PF
1.0PF
Price
Addition
(Percent
o f
Basic
Price)
Reduction
in
Ful l-Load
Efficiency
Multipl ier
Fo r
Transient
Reactance
Norma l
1.00 1.10 1.07
1.25
0
0. 0
1.000
N o t
More
Than
1.08
1.22 1.32
1.43
2
0.1
0.970
N o tMoreThan
1.15
1.32
1.46 1.60
4
0. 2
0.940
N o tMoreThan
1.23
1.42
1.58
1.75
6
0. 2
0.910
N o tMoreThan
1.31
1.52
1.70
1.88
8
0. 3
0.890
N o t
More
Than
1.38 1.59 1.78
1.97
10
0. 3
0.860
N o t
MoreThan
1.46
1.67
1.86
2.06
12.5
0. 4
0.825
N o tMoreThan 1.54
1.76 1.96
2.16 15
0. 4
0.790
N o tMoreThan
1.62
1.84
2.03
2.23
17.5
0. 4
0.760
N o tMore
Than
1.70 1.92
2.11
2.31
20
0. 4
0.730
N o tMoreThan
1.76
1.98
2.17 2.37 22.5
0. 5
0.705
N o tMore
Than
1.83
2.05
2.24 2.44
25
0. 5
0.680
N o t
MoreThan
1.89
2.11
2.30
2.50
27 .5
0. 5
0.655
N o tMoreThan
1.96 2.18
2.37 2.56
30
0. 5
0.630
N o t
More
Than
2.02
2.24
2.42
2.61
32.5
0. 6
0.605
N o tMore
Than
2.08 2.30
2.48 2.67 35
0. 6
0.580
N o tMoreThan
2.13
2.35
2.53
2.72
37.5
0. 6
0.560
N o t
More
Than
2.19 2.40 2.58 2.77
40
0. 6
0.540
N o tMoreThan
2.24 2.45 2.63 2.82
42.5
0. 7
0.520
N o tMoreThan
2.30
2.51
2.69
2.87
45
0. 7
0.500
N o tMore
Than
2.35
2.56 2.74 2.92
47.5
0. 7
0.480
N o t
More
Than
2.40
2.61
2.79
2.97
50
0. 7
0.460
N o tMore
Than
2.45 2.66
2.83
3.01
52.5
0. 7
0.445
N o tMoreThan
2.50
2.71
2.88
3.06
55
0. 7
0.430
/
ine-chargingan dcondensing
capacities.
ominal
values
or
hese
enerator
haracteristics
re
atisfactory
inal l
xcept
very
pecial
ases.
fthe eneratorwillbe
required
o
nergize
elatively
ong
H V
ransmission
lines,heine-chargingrequirementshouldbealculated
an d
eneratorwith
he roperharacteristics
pecified.
Theine-chargingapacityof
a
enerator
aving ormal
characteristics
an
be
ssumed
toqual .8of
itsnormal
ratingmultiplied y
tshort-circuitatio,
u t
annot
e
assumed
to
exceed
its
maximum
rating
fo r70C
temper-
ature
rise.
ften
it
will
bedesirable
to
operate
generators
as
ynchronousondensers.heapacityfo rwhich
they
ar e
designed
when
operating
over-excited
as
condensers
is
as
fol lows,unless
differentvalues
ar e
specified:
Power
Factor
.8 0
.9 0
.9 5
1.00
Condenser
Capacity
65
percent
55
percent
45
percent
35
percent
g.
Power
factor.
(1 )he ea t
enerated
within
machine
s unc-
tion
of
its
kV A
output;
thecapacity
rating
of
a
generator
is
usually
xpressed
n
erms
f
VAnd
oweractor.
(Larger
machine
atings
re
sually
iven
n
MV A
or
convenience.)hekilowattrating
is
the
kV A
ratingmulti-
pliedbythe
rated
powerfactor.he
power-factor
rating
fo rthe eneratorhouldbe
etermined fter
iving
on-
sideration
to
theloadan dthecharacteristics
of
thesystem
that
will
e
upplied
y
he
enerator.he
ffect
of
power
factor
ratingon
machine
apability
is
illustrated
in
Figure
3-1.
(2 )he oweractor
t
which
enerator
perates
is
affected
by
the
transmission
system
to
which
it
is
con-
nected.
ransmission
systems
ar e
designed
tohave
resis-
tiveharacteristics
t
heir
ated
ransmissionapacities.
Consequently,
enerator
onnected
o
ransmission
system
will
typically
operate
ator
nearunity
powerfactor
during
maximum
utput eriods.
During
ightly
oaded
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8
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3
s
&
C J I
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94
conditions,
owever,
he
eneratorma y
e
equired
o
assist
in
transmission
line
voltage
regulation.
generator
operating
nn
H Vransmissionystem
withelatively
short
ransmission
istances
will
ypically
e
equired
o
supplyreactivepower
(i.e.,
peratewithalaggingpower
factor
n
n
verexcited
ondition),
ue
o
he
nductive
characteristic
of
theunloadedtransmissionline.
gener-
ator
operated
on
along,
uncompensatedEH V
transmission
linewill
ypically
eequired
o
bsorb
eactive ower
(i.e.,
peratewith eading oweractor
n
n
nder-
excitedondition),
ue
o
heapacitive
haracteristic
of
the nloaded
ransmission
ine.
n
he
atter
ase,
he
generatorield
urrentequirements
re
ubstantially
below
ated
ield
urrents,
hu seducingheenerator
fieldtrength.
ithreducedfield
strength,he
enerator
operatescloser
to
itsstabilitylimit(see
Figure
3-1),
mak-
in gt
more
usceptibleo
ossofynchronism r ole
slipping
in
the
event
of
a
systemdisturbance.
(3 )t
s
ighly
esirable
ha t
he
enerator
e
designedfo rthepower
factor
at
whichitwill perate
n
order
omprove
ystem
tability.neneral,
nless
studiesndicatetherwise,heoweractorelected
should e .9 5
or
medium
ndarge enerators
nless
theywill e
t
he
nd
of
a
ongransmission
ine,
n
which
case
a
value
approaching
unity
ma ybe
desirable.
h . Reactances.
(1 )height
ifferent
eactancesf alient-pole
generator
ar e
of
interestin
machine
design,
machine
test-
ing,
nd
n
ystemtabilityndystemtability
model
studies.
ul l
iscussion
of
these
eactances
s
eyond
thecope
of
this
hapter, utan e
ound
n
lectrical
engineering
extsDawes947;
itzgerald
nd
Kingsley
1961; uchstein, loyd,nd
Conrad
954),
nd
ystem
stability
texts
an dstandards(IEEE399) .
(2 )othatedoltage
alues
f
ransientnd
subtransient
reactances
ar eusedincomputationsfo rdeter-
miningmomentaryatingnd
he
nterruptingatings
of
circuit
reakers.
ow ethrougheactancefhe
generator
nd
tep-up
ransformer
ombined
s esirable
fo rsystemstability.herenominalgenerator
an dtrans-
former
esign
eactances
o
ot
meet
ystem eeds,he
increase
n
ost
of
reducing
ither rbothhe enerator
an d
ransformer
eactances
ndhe
election
ofpecial
generator
eactance
hould
e
ubjectorconomic
study.
uch
tudyust
nclude
onsideration
f
space
nd
quipment
andlingequirements,
ince
reduction
n
eactance
ay
eccomplished
y
n
increaseingenerator
height
ordiameter,orboth.
(3 )
ypical
alues
of
transienteactancesor
arge
water
wheeleneratorsndicated
y
igure-2ren
accordancewith
ndustry
tandard ractice.
uaranteed
valuesf
ransient
eactancesil le
pproximately
10
percent
higher.
(4)veragevalues
of
standardreactancewillproba-
bly
besufficiently
close
to
actualvaluestodeterminethe
rating
of
high-voltagecircuitbreakers,an d
shouldbe
used
in
preliminary
calculationsfo rotherequipment.ssoon
as
esign
alculations
or
the
pecificmachine
re
vail-
able,he esign alueshould
be
sed
n
rechecking
the
computations
fo r
other
itemsof
plant
equipment.
i.
mortisseur
windings.
(1 )
mortisseur
windings
(also
referred
toas
damper
windings
inIEEE399;Dawes947;
Fitzgerald
an d
King-
sley
1961;
nd
uchstein,
loyd,
nd
Conrad
954)
re
essentially hort-circuited ri d
of
copper
onductors
n
theac e
f
ac h
of
he
alient olesn waterwheel
generator.
w o
ypes
of
amortisseur
windingsma y
e
specified.nne ,he oleac e
windings
re
o t
nter-
connectedwith
ac h
ther,
xcept
hrough
ontact
with
therotormetal.
nthesecond,thepolefacewindingsar e
intentionallyconnected
at
the
top
ndbottom
to
the
adja-
cent
damper
windings.
(2 )hemortisseurwinding
sof
majorimportance
to
the
stable
operation
ofthe
generator.
hile
thegener-
ator
s
perating
n
xactynchronismwith
he ower
system,
otating
ieldnd
otor
peed
xactly
matched,
there
s
o
urrent
n
he
amper
winding
nd
t
ssen-
tially
ha sno
effect
onthe
generator
operation.
f
thereis
a
mall
isturbance
n
he
owerystem,
nd
he
frequencytends
to
changeslightly,the
rotor
speedan dthe
rotating
ieldpeedwill elightly ifferent.
he
otor
mass
is
perturbed
when
synchronizing
power
tends
to
pull
the
otor
ack
ntoynchronismwithheystem.ha t
perturbation
endsoausehe
otor-shaft-turbine
unner
mass
to
scillateaboutitsaveragepositionasatorsional
pendulum.he
result
is
relatively
large
pulsations
in
the
energy
component
ofthe
generatorcurrent.n
worst
case,
theoscillationsca n
build
instead
of diminishing,resulting
inhe
eneratorpulling
ut
ofstep
withpossible
onse-
quential
damage.
(3 )
t
he
nset
f
he
scillations,
owever ,
he
amortisseurwinding eginso av etsffect.she
rotatingield
moves
n
elation
o
he
otor,urrent
s
induced
n
he
mortisseur
windings. Induction
motor
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94
action
esults,
nd
he
otor
s
ulled
ac k
oward
yn -
chronism
by
the
amortisseur
winding
action.
(4)
hemortisseur
damper)inding
s
of
mpor-
tance
n
ll
owerystems,
ut
venmoremportant
o
systems
ha t
en d
oward
nstability,
.e.,
ystems
ith
largeoads istantro m enerationesources,ndarge
intertie
loads.
(5 )
n llases,
onnectedmortisseurwindings
re
recommended.
f
the
windings
ar e
not
interconnected,the
current athetween
djacentwindings
s
hrough
he
field
ole
nd
he
otorim .hisendso
e
ig h
impedanceath,ndeduces
he
ffectiveness
f
he
winding,
s
wel l
s
esulting
n
eating
n
heurrent
path.
ac k
of
interconnectionleads
to
unevenheating
of
the
amper
windings,
heir
eterioration,nd
ltimately
damagetothe
damper
bars.
(6 )
he
mortisseurwinding
ls o
ndirectlyid s
n
reducing
generator
voltage
swings
under
somefaultcondi-
tions.t
does
this
by
contributing
to
the
reduction
of
the
ratio
of
the
uadraturereactancean d
thedirectaxisreac-
tance,X
q
/X
d
.
hi s
atioan
es
reat
s
.5
or
salient ole
enerator
with
o
mortisseurwinding,nd
ca n
e
sows
.1
fthe
alient
ole enerator
as
fully
interconnected
winding.
/
fficiencies.
he
value
of
efficiency
to
beused
in
preparing
thegenerator
specificationshould
be
as
high
as
ca n
be
economically
justified
andconsistent
with value
manufacturers
willuarantee
n
heir
ids.peednd
power
actor
atings
of
a
enerator
ffect
he
fficiency
slightly, uttheelection
of
theseharacteristics
s
ov -
erned
y
ther
onsiderations.
or
enerator
ofny
givenpeednd owe r
actor
ating,
esign
fficiencies
ar e
reduced
by
the
fol lowing:
(1 )
igher
Short-CircuitRatio
(see
paragraph
3-2e).
(2 )igher
Wl?
(see
paragraph
3-56).
(3 )
bove-Normal
Thrust.
Calculated
fficiencies
hould e btainedro mheup-
plier
as
oon
s
esign at afo rthe enerators
re
vail-
able.
hese esignfficiencieshouldbeuseduntiles t
values
ar eobtained.
3-3.
enerator
Neutral
Grounding
a .
eneral.
he
main
reasonsfo rgroundingtheneu-
trals
of
synchronous
enerators
re
o
imit vervoltages
on
he
enerators
ndonnected
quipmentunder
phase-
to-ground
ault
onditions,
ndo
ermithe
pplication
of
suitable
ground
fault
relaying.uitable
neutral
ground-
in gquipment
hould e rovided
orac h enerator
n
hydroelectric
power
plants.
he
generator
neutralsshould
be
rovided
with
urrent-limiting
evices
n
he
eutral
circuitsoimit
he
winding
ault
urrentsnd
esulting
mechanicaltresses
n
he
enerators
n
ccordancewith
IEEEC62.92.2equirements.lso,
enerator
ircuit
breakersreesigned
or
senig h
mpedance
grounded
systems,
where
the
phase-to-ground
short-circuit
current
will
not
exceed0A .ig himpedance rounding
with
istribution
ransformers
nd
econdary
esistors
s
themethodofchoicefo rwaterwheelgenerators.
b .hoicefrounding
ethod.
he
hoice
f
generatorneutralgrounding
type
fo r
each
installation,
an d
theelectionofthe
most
suitabletypend
rating
of
neu-
tral
rounding
quipment,
hould
e
made
fter
prepara-
tion
of
faultcurrentcalculationsndconsideration
of
the
fol lowing
factors:
(1 )
imitation
ofwindingfaultcurrentan d
resulting
mechanicalstresses
in
thegenerator.
(2 )imitationf
ransient
vervoltages
ue
o
switchingoperationsan darcinggrounds.
(3 )imitation
of
dynamicovervoltagestoground
on
the
unfaulted
phases.
(4)enerator
surge
protection
(see
paragraph
3-4).
(5 )
enerator
round
ault
elaying
se e
ara-
graph8-60(3)).
(6 )imitation
of
damage
at
the
fault.
(7 )
eutral
switchgearrequirements.
(8 )ost
of
neutral
groundingequipment.
c .
olidneutralgrounding.
olidneutral
rounding
is
heimplestroundingethod,
ince
ransient
overvoltagesan dovervoltages
to
groundon
the
unfaulted
phases uring
hase-to-groundaultsre el d
o mini-
mum.
olid
eutral
rounding
oes
roduce
maximum
groundault
urrent
nd
ossible
amaget
he
ault.
Solideutralgroundingis
not
recommended.
d .
eactoreutralrounding.eactoreutral
grounding
as
ertain
esirable
haracteristics
imilar
o
thoseofsolidneutralgrounding.It
is
a
preferred
method
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of
rounding
nases
here
eutral
urrent-limiting
devices
equired
oee tNSI/IEEEhort-circuit
requirementsnd
where
he
atio
f
theer oequence
reactance
o
he
ositive
equenceubtransienteactance
at
theault
does
not
exceed
6.0.
eactor
neutralground-
in g
imits
ransient
vervoltages
nd
vervoltages
o
ground
nhe
unfaulted
phases
oaf e alueswherehe
above
reactance
ratio oes
no t
exceedpproximately
6.0.
However ,
nmosthydro
pplications,
his
eactanceratio
approaches rexceeds .0 ,ndincethehighmpedance
distribution
transformer-secondary
resistorsystemismore
economical ,reactorneutralgroundingdoes
no t
findwide-
spreaduse
inhydroapplications.
e .
esistor
eutral
rounding.esistoreutral
grounding
ca nbeonsideredincaseswhereolidneutral
groundingr
eactor
eutral
rounding
ould
ot
e
satisfactory;whereeveral eneratorsre
aralleled
n
common
bus,
especially
in
the
case
of
generators
of
small
or
medium
VAating;
nd
where
here
re
o
xposed
overheadfeederssupplied
at
generatorvoltage.
heresis-
to r
is
sually
atedto
imitthe
eneratorneutral
urrent
duringa
phase-to-ground
faulttoavalue
between
00
an d
15 0 ercentofthe
enerator
ull-load
urrent.
ossible
damage
t
theault
s
hu s
materiallyreduced,
etuffi-
cient
groundfault
current
is
available
to
permit
the
appli-
cation
of
satisfactoryndelective roundaultrelaying.
The
echnique
oes
roduce
ig h
oltage
o
round,
exposingnsulationystems
f
quipmentonnected
o
the
generator
to
the
possibility
ofinsulationfailure.
/
istributionransformer-secondaryesistoreutral
grounding.
(1 )
hi s
s
hepreferredmethod
of
generator
neutral
grounding
an d
is ,
in
effect,
high-resistance
neutral
ground-
ing.hisshe
method
se dn
most
North
American
hydro
nstallationsbecause
he
ost
of
grounding
evices
an d eutral
witchgearor ther roundingmethods
s
excessive
duetothearge
values
ofgroundault
current.
Its
ls o
pplicableo
enerators
onnected irectly
o
delta-connected
windings
ofstep-up owerransformers,
especially
where
therear e
no
overheadfeederssupplied
at
generatorvoltage.
he
haracteristics
ofthis
method
of
grounding,ithespect
o
ransient
vervoltages
o
ground
n
he
nfaulted
hases
nd
he
equirement
or
the
se
f
ngrounded-neutral
ated
urgerresters
or
generator
surge
protection,
re
imilar
to
those
of
resistor
neutral
grounding.
(2 )ith
hisethod
f
rounding,
he
enerator
neutral
urrent, uring
phase-to-ground
ault,
s
imited
to
a
very
lo w
value,
usually
between
5 A
an d
5A,by
the
us e
of
a
elativelyow-ohm
esistor
huntedcrosshe
secondary
ofa
conventional
step-down
transformer
whose
primary
is
connected
inthegeneratorneutralcircuit.he
possible
amage
the
ault
s
herefore
east
of
an y
of
the
arious
rounding
methods.owever,
he
ype
of
generator
ground
fault
relaying
which
ca n
be
pplied
ha s
certainisadvantageshe nompared
o
he
elaying
whichca nbeused
with
othergroundingmethods.
ueto
relativelyow
elay
ensitivity,
onsiderable ortion
of
the
enerator
windings
ea rhe
eutral
nds
annot
e
protected
againstgroundaults,heelaying
is
not
elec-
tive,
an d
the
relay
sensitivity
fo r
ground
faultsexternal
to
the
enerator
aries
reatly
with
he
aultesistance
nd
theresistanceofthe
return
circuit
fo rgroundfaultcurrent.
TheVA
ating
of
the rounding
ransformerhould
e
based
n
the
apacitive
current
which
would
flowduring
a
hase-to-ground
ault
ith
he
enerator
eutral
ungrounded.
(3 )ue
o
heelativenfrequencend
hort
ura-
tion
of
ground
faults,
a
rating
of
25
to
00kV As
usually
adequateor
he
ransformer.he
oltage
ating
of
the
transformer
high-voltage
windingshould
be
equalto
rated
generatorvoltage,ndthe
ransformer
low-voltagewind-
in ghould
be
ated
40
V.
he
ating
of
the
econdary
resistor
s
ased n
making
heesistor
W
loss
t
east
equal
to
the
capacitive
faultkVA.
g.
Generatorneutral
equipment.
(1 )
n
utomatic
ir
ircuit
reaker
hould
e
ro -
vided
n
the
eutral ircuit
of
each
generator
whoseneu-
tral
s
olidly
rounded,
eactor
rounded,
r
esistor
grounded.
heircuit reaker
hould
e metal-clad,
drawouttype, ither -pole
r
-pole,
with
a
voltage
rat-
ing
t
east
qual
o
ated
enerator
oltage,nd
with
adequatemperenterruptingapacity,
t
ated oltage,
fo rhe
aximum
omentary
eutralurrenturing
single
hase-to-ground
ault.
or
enerator
eutral
er -
vice,
he
ircuitbreakers
ma y
be
pplied
orinterrupting
duties
p
o15
ercent
oftheir
ameplate
nterrupting
ratings.he n3-polebreakersar eused, ll
poles
hould
be
paralleled
onboth
line
an dload
sidesof
the
breaker.
(2 )ingle-poleir-break
isconnecthould
e
provided
nac h
enerator
eutral
ircuit
sing
istribu-
tionransformer-secondary
esistor
ype rounding.
he
disconnecthould
av e
oltageatingqualoated
generatorvoltage,
an d
shouldhavetheminimum
available
momentary
nd
ontinuousurrent
atings.
he
disconnect, istribution
ransformer,nd
econdary
esis-
to rshouldbenstalled
together
in
asuitablemetalnclo-
sure.
The
istributionransformerhould
e
of
the
ry
3-7
-
8/11/2019 Centrale Hidro
20/118
EM
1110-2-3006
30
J u n
94
type,an ditsspecificationsshould
require
a
typeof
insula-
tion
that
does
no t
require
a
heater
to
keep
moisture
outof
the
transformer.
3-4.eneratorSurgeProtection
a.
urgerotectionquipment.
ince ydroelectric
generators
ar e
air-cooled
an d
physically
large,itis
neither
practical
or
conomical
o
nsulatehe mor
s
ig h
impulse
withstand
evels
il-insulated
pparatusofthe
samevoltage
lass.
ecause
of
thisan dtherelativeost
of
procuringan dreplacing
or
repairing)
he
tatorwind-
ing,
uitableurge
rotection
quipment
hould e ro -
vided
or
ac h
enerator.hequipment
onsists
f
special
urge
rrestersor
rotectiongainst
ransient
overvoltage
nd
ightning
urges,
ndpecialapacitors
fo rlimitingtherate
of
rise
of
surge
oltages
n
ddition
to
limiting
their
magnitude.
b .
nsulation
mpulse
level.
he
impulse
levelofthe
stator
inding
nsulation
f
ew
enerators
s
approximatelyequal
to
the
crestvalue
of
the
factory
low-
frequencyithstandes t
oltage,r
bout
0. 5
kV
or
13.8-W generators.hempulse reakdownvoltagesfo r
surgerresters
or
2 > . - k V
enerator
rotectionre
approximately
5
kV
or
2-kV
rounded-neutral
ated
arresters,an d
approximately44
kV
fo r5kV
ungrounded-
neutralatedrresters.rounded-neutral
ated
urge
arresters
herefore
rovide
etter
protection
o
enerators
thanungrounded-neutralrated
arresters.
c .rounded-neutralatedrresters.o
orrectly
apply
rounded-neutral
ated
rresters
without
n
nac-
ceptable
is k
f
rrester
ailure,he
ower-frequency
voltage
pplied
cross
he
rrester
under
normal
r
ault
conditionsust o txceedhe
rrester
oltageating.
This
equirement
s
sual ly
et
fheatio
f
er o
sequence
reactance
to
positivesequencesubtransient
reac-
tanceat
the
fault,
or
a
single
phase-to-ground
fault,does
no txceedpproximately .0 .ince istributionrans-
former-secondary
esistor
rounding
oes
o t
meet
hi s
requirement,onlyunground
