grounding of standby

8/2/2019 Grounding of Standby

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GRoundinG o STAndby A

EmERGEncy PowER SySTEm

the per t prtet

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Lw a me Vltage

dstrbt Systes

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netral Grg Resstrs

-desg a Applat

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Syste Grg

-det a dferet

PRoducT GuidE

Hgh Resstae Grg

Systes

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Ar lash Hazars a Hgh

Resstae Grg

coRPoRATE mAnuAL

i-Gar crprat

i-GARd LiTERATuRE

.gar.


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me vltage geeratrs are t esge t thsta ll alt rret rg a sgle phasetgralt. Ths s the a reas that e vltage geeratrs are ete t a sste th ether l r

hgh peaes. There are a eths t gr geeratrs.

Aressg Gr alts mV Geeratrs

L ipeae Gre. A l peae gresste prses a et the geeratrs etral

teral t gr thrgh a peae as sh g, 1.

The resstr tpall lts gr alt rrets r 200 t

800 Aperes r a shrt rat. The alt rret s selete

rer t ze aage at the pt alt as ell as

prvg seletve rat the prtet sste.

As ell as zg the aage at the pt alt, l

peae gre sstes als ze shk hazars

ase stra rrets, ze theral a ehaal

stresses eqpet, a trl traset vervltages.

g. 1 L ipeae Gre Sste

g. 2 Varat Sgle Pt Gre Sste

The savatages the gre sste esre g. 3 are aresse th the sste g. 4. i th

sear the etrals are all ete tgether a there l exst l e retr path r a gr al

The er geeratrs gg le s als aresse.

g. 4 c netral Sgle Pt Gre Sste

There are 2 ajr savatages th

k sste, e eg the rlat

thr har rrets thrgh th

ete etrals, a the ther e

the plex servealt a geerat

wth the etrals all ete tgethe

a gr alt ahere the sste

elevate the ptetal the etral heth

the geeratr s ete t the sste

r t. Ths psses a saet hazar r a

persel rkg the geeratrs. Th

llg sheat aresses the sgpt gr th a artal etral. Th

eth s h spler tha the e

gre 3, hever the savatage s th

gre state the geeratrs he

t ete t the eletral sste.

g. 5 ZgZag Sgle Pt Gre Sste

g. 3 Varat Sgle Pt Gre Sste

A hr grg sste esg alls lexlt

As the geerat apalt th alt rease, as sh g. 2, the vale gr alt rret als

reases. As a exaple, r geeratrs are ete t a s the ax gr alt

rret a e ahere etee 200 A., l e geeratr s le, t 3200 A. all r geeratrs

are le th a 800 A l resstae gre sste. As re a re geeratrs are ete, the

avatages prevsl lste qkl sh.

The greatest raak ths tpe sste s tesse he a gr alt rs th the statr

g a geeratr. Experee has sh that the gr alt ll t e reve r the geeratr

eve thgh the geeratr reaker has pee. The geeratr ll te t sppl the rret t hrgh

the gr alt tl the el extat eas. The phsal aage ase t the geeratr s ase

the rat the alt a t the agte the alt.

Sgle Pt Gr Sste. Sgle

pt grg esres that l

e sre s gre at a gve

te. There are three as hh

ths a r. g. 3 shs a ltple

geerate ete sste here

etral slatrs esre that l e

resstr s ete t the eletral

sste at e te.

Ths sste s plex as the slatr sthes are eessar. it s als eessar t pleet a perat

prere r a k trasers. The ther savatage ths tpe sste s that the sste ll

ee gre shl the ete gre sre ee slate. Ths l pt the etresste at rsk. As geeratrs rap p a plae t serve the as ell l e gre tl the

are ete t the per sste.

mltple Pt Gre. The sheat sh g. 2 s a exaple a ltple pt gre. Ea

geeratg sre s gre thrgh ts grg resstr. There s rsk leavg a sre geerat

gre. There s als saet hazar he servg a geeratr.

wth a geeratrs ete, the at gr alt rret a exee levels that ll lt the aag

at the pt alt. Ths s extreel evet shl the pt alt r the statr g the geerat

wth the alt the statr g, alt rret l t e terrpte, eve th the rree a

terrpt the rt reaker etg the geeratr t the eletral strt sste. Ths tpe a

a ltple pt gre sste ll have severe aage the statr gs.


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Hgh ipeae Gre. A hgh peae gre sste prses a et t he geeratrs etral

teral t gr thrgh a peae as sh g, 1. The resstr tpall lts gr alt rrets t a l

vale r a extee rat. The alt rret s selete rer t e eqal t r greater tha the sste apatve

hargg rret.

The avatages the hgh peae gre sste are ers, al alt rret at the pt alt,

tt perat, a a ret traset vervltages as ar as the gre sste s ere.

oe savatage a hgh peae gre sste s the sestvt reqre r the etet a gr alt.

The gr alt rret the rer agte 10 Aperes, re sestve gr alt prtet s

eessar.

As the hargg rret reases large strt etrks r as re geeratrs are plae le, t a t e

easle t have a hgh peae gre sste.

The ptal slt s a at the l peae gre sste a the hgh peae gre

sste. The sste l eetvel e l resstae r all gr alts. i, hever the alt s a gr alt

th the geeratr, the sste l revert t a hgh peae gre sste a ze the aage. Ths

sheat s see g. 6.

g. 6 Hr Gre Sste

Ths sheat ates that the ax gr

alt rret s the rer agte 400

A., regarless h a sres are ete

t the sste,. Gr alts strea ll e

slate the reaker lsest t the alt seletve

rat a Gr alts th the statr ll

e slate the eretal shee sh g. 6,t slat ll l r the sppl reaker r

that partlar reaker. Ths ll leave the geeratr

a Hgh ipeae gre state a ze the

aage t the statr.g. 7 ZgZag Sgle Pt Gre Sste

Hr Grg. T

he geeratr sh g. 6 s gre thrgh

th a L ipeae a a Hgh ipeae eve. Ths sear

l all all the eets the L peae gre sstes

that all thrgh gr alts ll have the seletve rat, there

s als al aage at the pt the alt. The gr alt rret

l e lte t the s the L peae sste a the hgh

peae sste. i the ase sh the gr alt rret l

e 410 A. i the gr alt as strea the the slatg eve

lsest t the alt ll slate the gr alt. The tre eet thsshee s serve he a gr alt rs the statr g

i the gr alt rs th the statr g, the gr alt rret l e lte t 410 A. tl the

eretal prtet slates the geeratr r the sppl a pes the tatr r the LRG eve. Ths ltg

the gr alt t 10 A. tl the geeratr sls t stastll.

whe ltple ts are plae le a eah t s prtete the Hr sste, the tee ll e t have all

hrs etal. Ths l ase extreel hgh gr alt rret he the sste s L ipeae, a the

eets l e lst. T pesate r ths, the sheat a e regre t that g. 7 a all the eets

l e aga e experee.

Q. we have a 3.3kV sste th l e geeratr gre va a etral earthg resstr a the thergeeratrs are rg parallel. All three geeratrs are prve th a etral slatr, a at a te

l e the s ete. i the geeratr s e, the e selet the ther t e ete t the

etral earth. wh s l the geeratr gre a t re? Are the ther geeratrs atg, a

t, h t?

A. There are at least t a reass h i l t ree etg all three etrals t s:

1) crlatg rrets ll th etrals a geeratrs. Ths ll ase verheatg geeratrs (resltg

a eratg atr) a ther prles t har sses.

2) i the etral slatr s let lse hle the geeratr a rt reaker s pe, the a shk hazar exsts e tetral vltage rse rg gralts.

The a reas h ths grg shee s selete s t ree sts. Hever, ater atrg the eratg

r eah geeratr a the saet atr lsg a gr a gg t a gre sste, r rret sste

sgatl sts re tha a nGR, hh s tpall 3%5% the pre a e geeratr.

Q. what s the grg prate (sl r l resstae) r three 4160V, 1000kw geeratrs peratg ps a Level i (Le Saet) geeratr stallat a reqres hgh avalalt. The la s a 4160480V, 3000kVA

trasrer late 600 eet r the geeratrs. i asse hargg rrets st e sere.

A. Regarg sll grg the geeratr, there are hazars that st e sere e t the hgh gralt rr

iEEE St. 1411993 (Re bk Reee Prate r Eletr Per dstrt r istral Plats) Set 7.2.4 sta

hazar exsts r sll gre sstes r the severe ash, ar rg, a last hazar r a phasetgr a

a resstr etee the etral a gr, the gr alt rret s tpall ree t 5A l the apatve hargg

5A. Se the trasrers are ~600t r geeratrs, the apatve hargg rrets are pral < 5A (please hek r sr

geeratr terals; s, the hargg rret a e > 5A). Als, se r applat s hgh avalalt, i l re

(5A) the geeratrs t all r perat rg gralts.

iEEE St. 1411993 (Re bk Reee Prate r Eletr Per dstrt r istral Plats) Set 7.2.2 state

ar ash hazar, as there s th sll gre sstes, se the alt rret s lte t apprxatel 5A.S lt

alt t 5A, have ave the hazars th sll gre sstes.

i at, several geeratr aatrers reqre resstae grg as the geeratrs are t rate r gr alts as t

tes hgher tha threephase alts. iEEE St. 1421991 (Gree bk Reee Prate r Grg istral a

Per Sstes) Set 1.8.1 states, ulke a trasrer ... a geeratr ll sall have hgher tal gralt rre

phase alt rret the geeratr has a sll gre etral. Arg t nEmA, the geeratr s reqre t ths

threephase rret level less t s therse spee ...Ths s e t l zerseqee peae th the geerat

hgh earthalt rrets.

The resstr als sgatl rees a rlatg rrets, hh are tpall trple har s leag t verh

geeratr gs.

i tpall ree ether resstae grg eah sre r erve a etral the parallelg s va zgzag tra

resstae grg the erve etral (hh s t t e se r a las r ete t athg exept the resstr

i at, i l se HRG (5A) the 480V sstes as ell. or Applat Ges r este (.gar.)

etal.

HT netral Grg va Resstr

4160V Geeratr Gr


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QA

crt breaker Trppg drg Parallelg Geeratrs

Q. we have three 1000k geeratrs parallel perat. whe eah geeratr rs sgle perat, t peratesrall. whe e start t parallel the ts, the geeratr rt reaker trps a ates a gralt. bt

he e sale the gralt prtet the rt reakers, the geeratrs rs parallel, takg la. is t t

avsale t se these rt reakers th gralt prtet r geeratr parallelg?

A. All geeratrs reate a thr har (a trples) e t ratal pth gs. Geeratr gs are ratal pthe tree the er e trs a t trl hars. Eah ratal pth aels that har (.e. a 2/3 pth geeratr has

ver lttle thr har, a 4/5 pth has ver lttle th har, a s ). urtatel, l pth at elate all hars

sltaesl. As e s elate, thers rease. These hars rlate etee sstes etrals a assate grg

sste.

Relas are etetg ths rlatg rret a prvg a trp sgal. Hever, t s t a aetal rret. Hee, e reslt

s t se a rela that l trs aetal rret, hh all gralts are l aetal. Althgh have xe

the sae trppg prle, stll have rlatg har rrets that ase verheatg, ths, a eratg atr st e

apple. Geeratr aatrers sggest athg all thr har vltages pre eah ahe stalle sae pth

ahes. Eve th athe pthes, ll stll have a rlatg rret.

S r sste s sllgre, the the peae s l a these hars ase sgat aage th the geeratr

gs the r heat. i hghresstae grg s se, the the extra resstae the rlatg path rees the

hars t eglgle levels. Als, st geeratrs are t rate r gralts (as the te exee threephase alt levels e

t ts teral l zerseqee peae). S the reqre peae grg t ree the gr alt el threephase

alt levels.

whe shrzg geeratrs, there are several as t gr the etral. r exaple, eah geeratr a have ts grg

sste r e a e estalshe the shrzg s. i eah geeratr has ts grg sste, the t a perate as a

separatel erve sste. Hever, all are shrze, the eah geeratrs avalale alt rret s alatve at the pt

alt. r exaple, eah geeratr ha a 5A nGR a there ere t shrze geeratrs, the the ttal gralt at the

pt alt l e 5A x 2 = 10A. The ttal gr alt rret s epeet p the er shrze geeratrs at the

te alt. Ths a lea t rat sses.

Ather eth grg s at the shrzg s va etral ervg trasrer (.e. zgzag trasrer) a do noT

et athg t the etral the geeratrs. The avatage s that the ttal gralt rret s epeet p the

er shrze geeratrs a ll e xe.

i at, se the geeratrs etrals are sete, there at e a rlatg rrets. (Reeer, althgh the

geeratr etrals are sete, the sste s gre va zgzag trasrer.) Hever, the shrze s s t serve,

the the geeratrs a t sppl a la as the ll e gre.

dset Sth r nGR

Q. i r prjet, e have three geeratrs (11kV).The etral these geeratr are gre separatel thr nGR.These geeratrs a r parallel. or let reqres a eas setg e tte the etral earthg

et at eah geeratr, s that geeratrs a e sete r ateae. m qest s e reall

reqre these set sthes? i e t stall these sthes, hat prles a e ae?

A. i the etrals are ete tgether a the r thrgh a nGR, the es. A set sth s reqre as the etral s vltage rse th respet t gr rg a gralt. Ths vltage l a ll ak ee t the geeratr

gs.

i eah geeratr has ts nGR, the i l sggest that a set sth s t eee. wth the geeratrs mcb pe, a

pe rt s reate. There s ptetal rse. i r let stll ats a set sth, the i l stall e the gr

se (save e sg a 600V s Sw) the nGR a onLy pe he geeratr mcb s pe.

Shrzat Geeratrs

Q. r shrzg geeratrs eret ratgs, hat are the rtera r etral grg? what s at

A. whe shrzg geeratrs, there are several as t gr the etral. r exaple, eah geeratr a hgrg sste r e a e estalshe the shrzg s.

i eah geeratr has ts grg sste, the t a perate as a separatel erve sste. Hever, all are s

the eah geeratrs avalale alt rret s alatve at the ptalt. r exaple, eah geeratr ha a 40

there ere ve shrze geeratrs, the the ttal gralt at the ptalt l e 400A x 5 = 2000A. The t

alt rret s epeet p the er shrze geeratrs at the te alt. Ths a lea t rat

Ather eth grg s at the shrzg s a do noT et athg t the etral the geeratrs. Ths that the ttal gralt rret s epeet p the er shrze geeratrs a ll e xe. H

shrze s s t serve, the the geeratrs a t sppl a la as the ll e gre.

Ater eterg the lat the grg pt(s), st ee the tpe grg. The st

sll gre (SG) r resstae gre, ether HRG r LRG. i 600V r el (HRG), the gralt s tpall let

tl t s late, a the a es s ae t eatel sht the alte rt r prevet a tre hazar

rea the sste tl a re veet te arses t repar the alt. i 5kV a el, t s ether HRG r LRG, epe

sste apatve hargg rret. Sstes ave 15kV are tpall LRG a trp th 10 ses.

The avatage resstae grg verss sl grg s at least tl (please reer t r Applat G

este r rther sss RG vs. SG .gar.). Regarg shrzat, all geeratrs reate a thrr ha

trples e t ratal pth gs. These hars rlate etee sstes etrals a assate grg

SG s sse, the peae s ver l a these hars ase sgat aage th the geeratr gs.

the the extra resstae rees the hars t eglgle levels.

Als, st geeratrs are t rate r gralts (as the te exee threephase alt levels e t ts tera

seqee peae). S, the reqre peae grg t at least ree the gr alt el threephase al

Earth alt Prtet Alteratr

Q. we are peratg a 625kVA dG set th 500kw alteratr, here the star pt the alteratr s sle have plae cT r earthalt prtet the etral re the strea the alteratr the

ths aeptale? H s the alt ere the ST gg t e prtete?

A. The rret trasrer r earthalt prtet ees t e plae the geeratr etral t earth lk, s thatalt rret ll retr t the geeratr r the earth arre ths etraltearth lk ll e see. Ths s hl e

avalale r earth. S a se etral earthg at a ther lat s t alle a t ll sale the earth alt

Earth alts ahere the sste the la r le se (lg the geeratr g) ll e sese, a the

rret ll t e sese as t ll retl g t the geeratr.


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QA

Sthg Trasets casg Sppressr alre

Q. we have a 4160V 2.8mw geeratr stallat t a 5kV parallelg traser sth. The tlt eeer s r a 2500kVAgre wyE trasrer th etral. The e traser sth ees exstg ster 5kV sthgear. The e

geeratr s ete as the tlt trasrer s th threephase res th a gr. The etral a the gr at

the geeratr are t e. Te he traserrg r tlt t geeratr a lse trast e e have

l the APhase sppressr the rst la reaker th the sters sthgear. The Perc treaker

traser sth lks at vltage a reqe a rgs the t spes a the lks at the phase agle eree

etee the t sres a ll lse the geeratr reaker he the phase agle gets t ve egrees r less.

The se a war LS4 rela r ths t. Se there s ster etral, shl the geeratr etral e

e t the gr at the geeratr? cl the rret et setp rg the lse trast perat e

asg the sppressr t al?

A. it appears that the 4160V tlt sppl s sll gre a, r r esrpt, that the geeratr s gre. it s psslethat the Phase A srgesppress eve, hh st have ee selete r a sll gre sste, ll see phasetgr

vltage sgs ater the tlt reaker pes. Ths l ase the Phase A sppressr t l. wth the geeratr ale spplg the

la, the rret thrgh the sppressr he t als shl e qte sall perhaps 5A10A. S i a srprse that t has l te.

Please ver the rret a the vltage ratg the eve.

whe the geeratr s spplg the la, l pral at t reta the sll gre haratersts the sste. S

have t hes:

1) cet the geeratr etral t gr. Ths ll ata the phase vltage t gr ere a ater the trast a keep the

sste stale. The egatve aspet s that hle tlt a geeratrs are rg parallel, there l e a sall rlatg rret

thrgh the gr rve the alae s phasevltage a trple hars. Ather prle s that the zerseqee

peae the geeratr s saller tha the pstve seqee, s the phasetgr rret ll e hgh a l ase hgh

alt aage at the pt gralt.

2) y l have sall resstae (nGR) etee the geeratr etral a gr hh ll vere th fltes th sl

grg. i l sggest a resstr th letthrgh rret 400A r re ll keep the geeratr phasetgr vltages

alae. 10serate resstr l e apple th stale gralt rela.

Q. There are three 1100kw/480V/60Hz se a moPu (le peratg prt t). we are asste earthg. is t reqre t g r hghresstae grg geeratrs at the etral pt a

etral atg? Please ave.

A. The reqreet epes p r applat. i t s se g, the es, HRG sstes are t l reqrresstae tr (that tall trs the resstr tegrt) s als reqre all g es a staars.

petrle a/r heal altes, the es, t s a reqreet per g egeerg prates as HRG s stes have

as staar prate th these altes. i a ther applat, the i l sa es ase the llg:

i r qest, is t reqre t g r hgh resstae grg geeratrs at the etral pt a leave the et

asse that eat oR leave the etral atg(as gre sste) a that the geeratrs ll e para

i hghresstae grg (HRG) sstes, the etral s t atg. drg gralts, t s hel t letetra

respet t gr, hee, elatg the aagg traset vervltages assate th gre sstes.

other avatages th HRG are:

1) no ar ash hazar Resstr lts gr alts t 5A, ths, ar ash hazars assate th sll gre sst

all eletral alts are gralts, s a sple resstr lers r rsk persal jr r eath (a eqpet a

2) no aagg traset vervltages ugre sstes are sjete t severe traset vervltages ase

gralts a sste apatae.

3) Ree thr hars whe parallelg geeratrs, a thr har rret rlates etee geeratrs a

ag a etral resstr r eah ll sgatl ree ths rret t eglgle levels.

4) cts perat n sht reqre rg gralts, allg prt t te.

5) altlatg eatre Plsg sste alls eletra t qkl late gr alt.

6) Ree gralt rrets mst geeratrs have gralt rrets ave threephase alt rrets a areths hgher alt rret. S, st aatrers reqre peae grg t ree the gralt rret el

alt rret level.

HRG sstes are the saest a least expesve sste avalale ta. iEEE spprts ths sag, A saet hazar ex

gre sstes r the severe ash, ar rg, a last hazar r a phaset gr alt.(iEEE St. 1

Re bk).

ugre sstes a experee aagg traset vervltages a lak the alt t late gralts

ather ager t persel.

Please reeer that HRG sstes, the etral at e strte. S, have las reqrg 277V, a s

trasrer a e ae t serve the 277V pael. The st savgs t strtg the etral, saller gr re

eatre the mcb ll re tha pa r the slat trasrer.

i sar, HRG saves e sg less pper (ver expesve aas) a akes sstes saer ela

ete ave.

Earth alt Prtet Alteratr

Q. A 480V, we ete geeratr, resstvel gre, ees a 480V we 4160V we trasrer, th etralssll gre. i ersta that the ee trasrer s t a gr sre, et zer seqee rrets ll pass

thrgh the gs. i the evet a gr alt the 4160V sste, the gr rret ll tr t get ak t the

geeratr etral, thrgh the grg resstr. The zer seqee rrets the 480V gs st therere e

eqal t the zerseqee rrets the 4160V g. what s t lear t e, s the ax vltage the grg

resstr ll e sjete t; is t 277V r 2402V?

A. b sll grg th ses the stepp trasrer, all zerseqee rrets t . The vltage arss the resstrll e 277V.

480V Geeratr Grg


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6 QA

Geeratr Grg Pt

Q. i at t ask at the geeratr grg pt a h e se t?

A. iEEE St. 1421991 (Gree bk Reee Prate r Grg istral a ceral Per Sstes) Set 1.4.2states, ners avatages are attrte t gre sstes, lg greater saet, ree r exessve sste ver

vltages that a r gre sstes rg arg, resat r earresat gralts, a easer etet a

lat gr alts he the r.

oK, that e have estalshe h ee t gr the etral, lets sss h t gr the etral. i eetvel

gr the etral, have jst replae the hazars th gre sstes th e hazars the r ar ash / lasthazars assate th sll gre sstes.

iEEE St. 1411993 (Re bk Reee Prate r Grg istral a ceral Per Sstes) Set 7.2.4 states, A

saet hazar exsts r sll gre sstes r the severe ash, ar rg, a last hazar r a phasetgr alt.

r ths reas, iEEE rees resstae grg.

iEEE St. 1421991 (Gree bk) Set 1.4.3 states, The reass r ltg the rret resstae grg a e e r re

the llg:

1) T ree rg a eltg eets alte eletr eqpet, sh as sthgear, trasrers, ales, a rtatg ahes.

2) T ree ehaal stresses rts a apparats arrg alt rrets.

3) T ree eletrshk hazars t persel ase stra gralt rrets the gr retr path.

4) T ree the ar last r ash hazar t persel h a have aetall ase r h happe t e lse prxt t

the gralt.

5) T ree the etar levltage p ase the learg a gralt.

6) T sere trl traset vervltages hle at the sae te avg the sht a alt rt the rree

the rst gralt (hghresstae grg).

iEEE St 1411993 (Re bk) Set 7.2.2 states, There s ar ash hazar, as there s th sll gre sstes, se the alt

rret s lte t apprxatel 5A.

As a see, t s est t t l gr the etral, t gr thrgh hghresstae (tpall 5A) r all sstes < 600V a

st sstes > 600V t 5kV. r sstes > 5kV, lresstae grg (tpall 200A r 400A) s se.

Jst a qk te at resae grg: resstae grg s preerre the uS stl e t es a plext.

Resstae grg s a passve eve that perrs epeet sste tplg a reqe, hereas resae grg

st aapt t sste apatae.

Resae grg ses a tr t reate a peae t ath the sste apatae peae. i g s, th

pets ael a the reslt s a sall resstve gralt rret.

dsavatages resae grg: 1) Tpall the tae s slghtl larger t av a tre resae t ( t, a ver

vltage t ll r) 2) Sste apatae tall hages as eeers are rght a le (s trg sste

st e stalle a tr st e varale) 3) cst r trg a tr varalt are hgh 4) Phsal sze tr ssgatl larger tha resstr.

Resstae grg ers a xe gralt rret epeet sste tplg. Hever, the xe rret st e larger

tha the sste apatve hargg rret. S, a vale 200400A s sall selete.

Q. we are the press stallg a 3x5.5mw,11KV, 50hz gas tre geeratr. The star pt the altee gre va a etral gr resstr (nGR). ca etere the vale the resstr a the rat

rret trasrer?

A. i ree sg lresstae grg (LRG) e t the vltage a apat. At 11kV a 3 x 5.5mVA, t(mVA) ates the sste s large ( ters ttal legth all the eeer ales, hh are tpall the greatest

sste apatve hargg rret) a the vltage es hgher ats sste apatve hargg rret. The

trtr t sste apatve hargg rret s srge arrestrs.

i ths s a tete geeratr, the i l ree hghresstae gre (10A15A) t ze alt a

there s ver lte er sall eeers (resltg a l sste apatve hargg rret).

i l ree 200A as ths s eg the str staar. The nGR s etere takg the letetral v

/ 1.73 = 6.36kV) ve esre rret (200A) t get hs (31.8hs). mst peple l all the alt t e the s

ses r less. S, the nGR l e rate r 200A /10 ses. Jst ake sre that the prtetve relag shee le

th 10 ses. y a ether se a 200:5 r a 100:5 rat cT.

i geeral, the ler the alt rret, the ler s the aage at the alt. Therere, t s esrale t keep the alt rre

pssle. i mV trs are eg prtete the keepg the alt rret l als helps lerg the aage t the la

the alt pt the evet a alt the statr g. i e ete tr gs, the rvg vltage r the g

rees as the alt lat ves lser t the s tar pt, hee, gralt rela st e set sestve egh t et

a sfet at rret st . Ths ll als tate h l a g th the resstr letthrgh rret

netral Gr Resstr Vale r a Per Stat

Q. i have a 750kw geeratr set a stral plat. m qest s shl i gr the etral geeratr terals? i s, h shl i sze the GEc? ive hear setes ths ase s t sere a s

erve sste, a the etral shl t e gre.

A. Lvltage geeratrs shl l e sll gre the las the ee are rre las a st haveGeeratrs that ee threere las t ee t e sll gre. istea the shl e hghresstae gr

gralt rret. Geeratrs are t rae r the gr alt rret that a r he sll gre. Geer

hgher gralt rret tha threephase alt rret. Trasrers t experee ths phee.

At a rate, assg st sll gr the geeratr etral r r applat, here are r rles:

1. i the atat traser sth (ATS) s threeple tpe th a sl etral teral, the st t gr the geer

at the geeratr; stea st et the geeratr etral t the etral teral the ATS, hh s tr

etral the ral per sre trasrer. The etral the trasrer ll e sll gre at the trasr

ll als e the grg pt r the etral r geeratr. whe have a threeple ATS th a sl etral,

geeratr s t a separatelerve sre.

2. i r ATS s ether a threeple th a verlappg etral tpe, r a rple tpe, the r geeratr ll e a

erve sre. i ths ase, the etrals the trasrer a geeratr ll t e ete tgether, a stgeeratr etral at the geeratr.

3. i r ATS s a threeple l th etral teral a r la s threere, the r geeratr s a separate

sre a a gr the etral at the geeratr. Hever, as ave, staars sh as nEmA mG 12003 mtrs a

(Set 32.34), a the iEEE Gree bk grg iEEE St. 142 (Set 1.8), ree that geeratrs t e sll

less the are rate r sh t (hh the rarel are).

Geeratr Sste Gr cet

grounding of standby

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