Barzam A.B. Automation in Electrical Power Systems (Системная автоматика)

CEAPEER

T'WO

o tll D--f -- n----d^--

a-

tu.

r\eYlew

({uf

rrr('rr5

1. What is the difference

between

the astatic

and static

characteristics

of

voltage

regt-

lation?

2. What is

current

stabilization. and

cqrr-elt compeusation

in voltage

regulation

devices?

Explain

the

purpose

of each

and

field

of

application.

3.

Hoq' are

the specifie-d reactive }oads

distributed

between

paralleled

geDerators

work-

ing

into

tbe

generatbr

voltage

busbars?

"

4. How ar-e

tbe

specified

ieactive

loads

distributed among

generator-power

transformer

sets

working into

eonimon

busbars? Wby

is

it

Decessary to

olJerve

a

deiinite

distribution

of

reactive loads

among the

generators

and astatic voitage

reguiatorc

under such

operating

conditions?

5.

Expiain

voltage

reguiation

in

power

systems.

Wbf is

it insufficient

to

use AEC

device

solely

for

voltage

reguiation of slnchronous

machines?

-

6. Describe

group

eJcitation regulation

o_f

generators

at

a

multiunit power

station.

Wbat

is

its

purpose

and

possible

application?

.

7.

Expiain

t'lre purpos€

and

possihility

-of

use of automatic voltage

regulators

controlling

the transformation

ratio

of Dower

transformers.

8. Why is it

possibie

to dhange the

voltage }evel

at a node

of a

power

system by

con-

pectlng

lumped_-capacitance banks? Under wbat conditions

should

the

banks

of capacitors

be disconnected?

9.

\4rhat

is

the

purpose

of automatic

force

(capacitor

banks

at tbe receiving end) and

10.

Describe

progranmed

voltage regtl

11,

Erplain

automatic rezulation

of

vol

u'ith utilizition of a

controlied

reactor and <

metbod

as eompared to autornat,ic res"ulation

to change

'"he

oapacitance current

vilue?

Ch,apter

Th,ree

3-1.

General

The

excitation

s}'stems

and

the

field

discirarge

devices

oJ svnchronous

getre-

rators

and

motor*s

are

considered

in

detail

ilG;il"oks

on synchronous

machine

operation'

This

chapter

presents

Tp:

principie-*lescribing

the

development

of

the

above-mentioned

systems

which

as-sure

correct

operation

oJ

automatic

power

system

control

assemblies

and protective

relayinf

;;;i;;;."'

There

are

separare

excitation

systems

in

*,hich

th;;u;pii-

;

exciting

cur_

rent

to

the

field

winding

of

a

sytchronous

-r*iiior

is

Jr'om

"n

irrarpendent

EaY(-Tm A Ttrrl tr ct\r6m-r r^

ElN-iJi

iAi

iu.i{

S Xiji.iifiis

AND

AUTOMATIC

FIELD

DISCEARGE

DEVICES

OF

S}'I{CBiOIVaUS

MACEINES

,fmat

ltfutecfton

Fig.

3-1. FDC

witlr

rotor

winding

changed

over

r€sistor

.R,

connected

into

exciter

1o

discirarge

resjstor

.R,

and

Ireld

circuit

Figure

3-1

illustrates

a

widel!

used

oaiiant

of

exciter

r

'6sre

e-r

*ruDr'Jr'rtris

a

wrQely

usec

varlant

of

.exciter

circuit

ernployed

in

conjunction

with

a

field

diseharge

control

irnCl

and

A66r;--s1]

1tr;hen rho

{BQts-s1.

When

the

6.

r

t4?,crl

=Ig

E:KCITATION

SYSTEMS

AND

AUTOMATIC

FDC

DEVICES

85

84

CEAPTER

1IENEE

circuit

is

of

t.he

seif-excitation

type

the continuous

current

generator

is moua-

ted

directly

on

the shatt

of

the

synchronous

gensrator

rotor. If

the

continuous

curuent

generator (exciter)

is driven

by

an indivitiuai

motor suppiied from

the

power

s1'stem,

use is made o{ separate excitation.

To

improve

the

reliability of

excitation systems, the tendencv

is now

to

replace

d.c.

commutator

machines

by

semiconductor

devices.

,g-*:l1t-"-t^:tl |::chfrge

its

fieid.

These

circumstances

have

been

considered

r!

v$qIJrErD

-t

a

uu

z.

^_"'|:""^":t_li::r...

yilh

the

srate

standard

Gosr,

rhe

excitarion

sysrems

must

eiisure

an

exci'ua'r,ion

forcing

muitipiiciiy

factor

of

not

less

than

i to"renerernrs

and

syucrlrono.us

c-apacitors,

whiie

the

rate

of

excitation

rise

;i;;f;"ffff;

]ess

than

2 unit,s

of

-ercitation/second.

The

fieid

djschar-ge

control (FDC)

di.sconnects

the

excitation

ri.rcuit

of

the

rotor

winding

from

the

d.c,.

source

or another

method

i.

"r"a

io-*oo

the

current

fios'

in

the

rotor

circuit,

such

as

the

cuttinf

out

of -ssnissuductor

devices.

The

action

of

the

FDC

is

more

efJective

*[r"-tn"

stator

emf quickit

d*;;;

the

value

at

which

arc

self-extinguishiog_occ,rrs

il

;il;t"il-*li.

to

the

srator

insulation'

Self-extinguishing

of

irc

uruiitl'

o.r"".

at

b00

volts

oi

less.

The

resi-

dual

emf

due

to

thJ

residuil

magretizaiion

does

not

exceed

ls0-200

volts-

The

functioning

of the

FDC

is

co'mpulsory

when

fauits

o"r,r,

irrride

the

gene-

rator'

The generg-tol

operation

is

allowed

witUout

exiitation

during

self-syn-

chronization

until

the generator

reaches..th.e

hlpo-.yochronous

speed

and

the

Igtol

winding

is

changed

over

from

the

discharliog

iesistance

to

carry

the

full

field

current.

Disconnection

of the Fl^)C ,].r.,ri.., ?,

tor

result*io

".yo.tronous

tperation

witir

resperr

rJrT.H;1tJ:1.::#"

senera-

-

If

reserve

power

is

avaiiable

in-a power

f;.t"*,

the'generriot.

which

lose

their

excitation

are

automatically'

did;;;;tea""s

the

b1o-cking

c-ontacts

of the

FDC

device

send

,

triP

signal

i9

tle

outpui-t.l"y--

oi-tn.

pioi"ction

s'srem.

With-a

shortage

of

a3tive

p-o*nr

in

|he

por,-*

ri=ten;'r,he

tnrbogei;;ffif'";;t

be.allowed

to

operate

v'ithout

excitation

for

some

time

(1s

6-30;;;r;;i

provided

the

active

load_

of the

generator-in

..i,rr"hroooo=

Jpur.ii"n

is

reduced

to

a value

approximatelv

40 pEr

cent

of the

rating

so that

the

generator

is

protected

against

current

overioading.

\vith

the

TGv--200

(TrB-200;

aia

rc\r-300_-(TrB-300)

rurbogeuerators

emplgrling^gas-discharge

tube

exciiation

and

rhe

TVv

ifgBL'{oili,

rvrt

-2aa-z

and

TV\t--320-2

cran4Iaf npc -.]ri^'L

--,^-:+,-.4: --

roa*iri^-^ _,-6^:"::.:,::"-:X"l

ubc

err{,llarlon

energ},

Irom

-semjconductor

rvvlrrrsr;t

ulJtrrdLru!

ur tlle

rIJu

ogvlces

and

arc

extinction

ma-v

causg

overvol-

tages

dangerous

to

the

insulation

materials

of

rhe

;";;;.-\ilt;d;lirectivesrs-lj

prescribe

the

use

of.discharges

operaring

at 2.4

u1;

[i..2

kv;;;i'tl

protec.r

the

rotor

iasuiation

against

rupiures.

To

prevent

dangerous

bverload

of rotors

having

forcecl

winding

cooling,

their

excitation

control

devices

are

furnished

rvith"

r iot"ing-lititrr.

In

FDC

devices

which

su'itch

the

rotor

oindiog.

t;-

;;;..]r*rg.

resistor

(Fig'

3-1),

the

stored

electromagnetic

energi'ls

aisiipited

in

the

1irm

of

heat

by

resistor

ft/. The

greater

this

reiist?ng.e,t[e

rrigtrer

ii..

"oii*g;"*;ors

the

rotor

terninals

and

the

quicker

the

field

discharge

iro"*r..

The

p;t;ir.iur*

voltase

across

the

rotor

terminals-d-epencls

on

the

iisuiation

effectiven;*

U;;"iIrTf;;

resistance

is

four-

to

five-fold

of the

rotor

u.inding

v'hen

in

the

warmed

state-

Resistance

R2 is

about

tr0-fold

the

resistance

of tle

exciter

fieid

coil

again

in

the

warmed

ilondition.

\47hen

the.generator^is

idling

tire

field

discharge

time

i-s

S

Lo

T

s.

The

rotor

current

and

the

value

of

emf

drop

foilows

the

expEnentiai

curve

(Fig.

B€).

Th;

s

t

0

0.5

1.0

t.5

Fic.

3-2.

Determining

tbe

mean

rate of

excitation

rise

Fig. 3-3. Changes

in

generator voltage after

operat,ion

of FDC

according

to

Fig.

3-1

(no-

]oad

runnins):

troc is

FDC

operating

time

\'

\

CE.A.PTER

TEREE

EXCITA?TON

SYSTE,MS

AND

AUTOMArIC

FDC

DE\rICES

differential

equation

describing

the

rotor

current change

has

the

L

#i-

(ftr

1-

r) i:

g

-

?

(FI*t)

i:

Ioe

r'

cunent in

the

rotor

winding

inductance

and

resistance

of the

rotor

winding

resistance

s'hich

the

FDC

device

connects to

the

terminals

T,bi"k

damage

by

reverse-cument

circuit

breakers

with ono-chnr orrrnnn*i^

reeiosure.

'i'he

auxiiiary

generator

has

an

AEc

d;;i",

*ita

"";;ffffiil;;

an

electtomagnetic

volta-ge

corrector.

-

GaS<Ilsclnrge

tube

egci,ter

wi,th

a seri.p,s-rnntzpnlorl rsnsn{^*^-rc-a1

diagram

variant

for

this

excirer

is showa

i"

ii[::

d'.\;L";"::;;*:;J".lJ#Xil

hence

g'here

r

-

L,r:

frr:

form

(3-1)

(3_2)

rotor

winding

-With -the

gas-discharge

tube

or

thyristor

excitation,

the

fieid

is

effectiveiv

and

rapidlv

discharged

(suppressed)

b1,

inver-ting

the

exciter

and forcing

ri-"f-

taneouslr

the

excitation

to the

upper

critical

value

dictated

b1'

the

rotor wind-

ing

insulation.

The field

discharge time

approaohe-q

here the

theoreticai

value.

3-2.

Excit"ers

Using

Gas-Discharge

Tubes

, ,i',.

.

and Thyristors

Gas-disclwrge

tube

ezci.ters

suppti.cd

from

a.n

autili.arg

generatorls-zl.

Used

a,s t-he

auxiliary generator

(Fig.

3-11 is three-phase

gener"io.

Z

connected

to

the

shaft

of

tbe

main generator.

The

field

coil

oi

tnis

generator

is supplied

with

rectified

current

from

exciter 2

which

is a

permanent--magnet

elevatr"Oltr.qrr"orii

three-phase

generator.

The

field

of

the

main

senerator ii suonlied th".,.'.,oh or.-

discharse

tube

rectifiers

from auxiliarv trans"fnrmo'-4 ho-,;.i.Ii.rt"--l^-,,r.-r;-::;

'

Gasdischar-ge

exciiaiion

circuit

fad

from

aux'iary

generaror

are

supplied

from

anode

transformer

6

which

is

eonnecl,ed

via

the

winding

of

a

series

transformeJ

to

the

stato.

*'olt^g,

;i'

;[.-"generator.

T]re

excitation

is

conirolled

b1'

AEc

5

connect*d

to

insirument-transformer

J.

Tiie

automatic

excitation

control

acts

upon

the

mercur],_arc

rectifiers

via

eontrol

cabinet

4

which

is

supplied

from

hius.

circuit

transformer

2.

when

short-circuit

fauits

occur

arrd

cause

the

voltag*

*"tori

the

siator

tliljn*i,

to

drop

the

power

supply

to

the

rectifiers

i-t

contiuir.d

f.;;

transform",

id,r.

to

current

in

the

winding

-serjes

connected

with

the

gro*."L,

shtor

winding.

Th,

;;;ifi".r"".,

protected

against

reverse

currents

by

circuit

;;;k#";-'""

An

advantase

of

this

excit;;lr-in

thai

it'uses.no

rorating

parts.

The

gas_

*,tt1?1-t

tube-excit"t.

"tit-iri-og

til

uroo"--lo?o*"a

circuft^"."

*ort,

pro-

^-.-9:::r-respot&e

exciters

employing^

th.yri.stors.

The

circuits

for

excitation

of

synchroriorrs

machines

with

thb

uie

oi

thi,riiior,

.r*-ri*ilar

to

the

excitation

cir_

t{.sky

CTIAP{TtsR

TIIRE.E

u'CTTA"ION

SYSTEUS

AND AI}TOTT.ATIC

TDC

DEVICES

89

cuits

utilizing

controlled

gas-discharge

devices'

shows

a

block

diagran

of

the th-vristor

exciter

bogenerator

plant-

for

synchronous

661613[8-ar

B5'*'ay

of illustration

Fig.

3-7

developed

at

the

Kharkov

tur-

s

-61.

fnn.AIC

device

q,/

dultlrorlt

getTeroior

fDC

device

When the motor

is

started the thyristor

is

short-circuited to

starting resistor

.R,

Due to the

effect of

the

induction

torgue,

the

motor spoeds up to

a

hypo-

sYt*"onous

speed. The current measu-

rements

in

the

.R, circuit

are taken

from the starting

resistor

protection

uuit

S,RP

which

measures

the

voltage

drop

across the voltage

transmitter

VT,

tb.e

voltage

being

taken

from the

terminais

of

a saturable

inductor. The

SRP

unit

acts

on

the

controi

pulse

shaping

unit P,9[i. When the

hypo-

synchronous

speed has

been

reached,

the .9^RP

unit

cuts off

thyristors

ThI

and TIyZ and with the

aid

of

the PSU

triggers

the thyristor

unit

into

conduc-

tion,

thus

feeding

the

field

current

from the

supply

transformer

to the

rotor v'inding.

If

the motor

is at fault

and

its

protection

is

functioning, a

sig-

nal

is ,sent

f,o

the

S,RP unit s'hich

makesthi,'iistors

Thi and

Th2 conduci

and

simuitaneousll: cut

off

the thyris-

tor

unit.

Tbus

the

field

is discharged

and

the

motor is

switched to

the start-

ing duty.

Similariy,

the

^SfiP

unit

ma-v

be used

to

change the

st'nchronous

mo-

tor to

operation

with

removed excita-

tion

and

discharged fieid

for

subse-

quetrt

self-s_vnchronization

of

the

motor

-after

recovery

of

the

stator

terminal

voltage.

The

forcing

iimiter

unit

FlU

is

connected

to

the

rotor winding

circuit

via

d.c.

transformerc

DCT. When

the

current

fiol1' in

the

rotor

winding

circuit

exceeds

the

rated

value

the

FLU

is

nouconductive.

The

rotor winding

via thyristor

sp'itches

fft.i

and

Tht-

Fig.

3-6. Gas-discbarge

excitation

circuit

with

series connection

of supplS' transfornrer

into

generator

stator circ.uit

Fig. 3-5.

Gas-discharge

excitation device

energized from

auxiliary

generator

iounted

on

the

main

generator

shaft'

e

-

contacts

of

anode

re"ersgurrent circuit

breakers.

with

oneshot

reclosure;

Du and

ji

-

di6ch-aryet-'aiii-iorie"f-ti-161une

resrstor.

to

protect

.agains.t

ov.ervoitages.which

mav

i,t"ut-*ften-iic

ii-lnieiiupieC

in

valves or

r*'hen

'irnode

circuit

breakers

colDe

into

actiott;

Ii

-

conracror

coni"if

iu-tiine

in

rCsistor R

for

Gtarting b-l

self'synchronization

metbod

acts

upon

the

control unit

CD

which

in turn

reduces

the current

in

the

fieid

,*

+1"

$s

-E€

'ets

bi

F,

FE+

e:.I

:\\

iJ\;

i'e

t

______-J

---

int

power

suppl-v

to-

the

-thyristor

.onnr."tiln

transfoimer

through

rectifier

CBAPTER

TEREE

sequence

of

oPerations

is

performed

by

the

sc

unit

whioh

responds

to the

stator

-ra"

of

a biower

controlled

by

suppl-v

unit

is from

a

step-down

doubie-wye

bridges.

To

cool

the_

assembll-,

use

,is

unit

,SU

with

the aid. oI contacLo!

K.

Fig.

Block

diagram

of

thyristor

excitation

slstem

E)ICITATION SYSTEDIS

AND AUTOMATIC

FDC DEVICES

Brushless

Excitation

Syste,rn

Mounted

on

the

shaft

of

rotor

/

(Fig.

3-8a)

is

the

stator

of

auxiiiary

generator

2

which revolves

togefher

u'ith rectifiers

3 and

field

coil

4

of

the synchronous

motor. Stator winding

5

of

the synchronous motor

is connected

to three-phase

Cont,-.ol

uot/

t

.9f

l4

i-f.

I

T

I

L

_J

L

_J

{b)

Fig.

3-8.

Brus\leq

excitation system

(a)

synchronous

motor;

J

-

g.vnchronous

motor

sbaft

axis;

I

-

stator of auxiliar-v-

gene-

rator

carried by the

machine

shaft;

J

-

rectifier carried by the

macbine shaft:

4

-

syn-

ehronous

motor

exciter

(reyolves

together

with

shaft); J

-

synchronous

motor

stator;

6

-

field

coil

of auxiliary

ceneratorsijlirT;)flJ"li:-q

macbine with

cascade asynchronoue-

mains in

the

usual

manner. Field

coil

6 of

the

auxiliary

generator

is

supplied

either

with direct current

or

with

rectified

alternating

current.

The

value

of

the

current

in

the field

coil

4

of

the main

unit is changed

by

varying

the

field

cur-

rent

in

coi] 6 of

'the

auxil.iary

generator

n'hic.h

thus

serves

as

if

a subexciter.

Figure

3-8b

illustrates how

synchronous

generators

can

be used

s'ith

a

brush-

less

eicitation

system.

The

shaft Sia

of

the s1'nchronous

machine

SIW'

carries

a field

coil FC.

Ttre same shaft

carries

rectifiers ER,

secondary

winding

of

A

B

;ing

part

of

the

resistance

.R.

is

to

}ower

listof

when

an

overvoltage

occurs

during

rvision

is

made

to

inverse

the current

ry

sending

the

signai

a;,,o

from

the con-

I

the

control

Pulse

shaPer.

CEAPTER

,IEREE

93

92

asYlchronous

stator

winding

of

auxiliary-synghronous

exciter

ion: crrnr.hrionous exciter

(EFC\

is

supplied

fron

EXCITATION

SYSTRTI{S

AND

.AUTOMATIC

TDC

DEVICES

erator

ilFG

is driven

by

the

turbogenerator shaft

on whicb

the

rotor of

maln

gensraf,or

ilorling

onup

To

storage

batlery

Io backup

etciter

forctng

oroup

___rl

ii

I

rl

l_______

-------r

I

Fig. 3-10.

Schematic diagram

of

gas-dischlrgg t_q!g

excitation of

turbogenera-

tor TGV-300

(TI-B-30U)

G

-

generator

stator;

.R

*

generator

rotor:--Rf

-

rectifying

transformer;

!3--

balanc-

ing i'eactor; R?

-

bboet€r

tiaruforroer;

H'VG

-

workilt*

group

ol valves;

FyG-forcrng-

gr"oup

ot

vaives:

GC-W, GC;F

are

derices lor

grid.

control

ol

working and

torcing

groups

of

iifs&;

FpS-ti

and RPs-F-rotating

phast

sbifters

o.f

.

working and

forcing

gloups

of

"at"es;

bp-c-t.T'and

SPs-F

are staticphaie

shiftersof

working and

forcing

groups

of

Talves;

FDC

-

f

ield

diseharge

controll AEg-autopatic

excttalron

contFoller

L

The

rotor

of

high-frequency

generator HFG

carries

no

field

coils.

The ooils

are Iocated

in

the

ilots of its

stator.

The

a.c.

windings

are fitted

in

the

same

siots.

exciter

AE,

ard

i#;,Jil#=r;;";--se

v,hich

ma1.

ie

influenced

by

the contror

unit.

The

main

"oo#Jt

;lf.;t

*

iUt

litta

curreut

fiow

in

the

rotor

winding

(FC)

of

svnchronous

machine

^!M

is

acconpiish."g

irv

ihe

controi

uui'r,

^r,hrough .uhe

ririii'o'*i"J*g

of

as-vnchronous

exciter

AE'

3-4.

Exeitation

Systems

of

Large

Turbogenerators

For

powerful

electric

machines'

use

-is ry99

either

of

a

dynamoelectric

high-frequency

excitation

system

(for

the

T\/a/

turbosenerators)

or

a

gas-

discharge

tube

exoitation

slisteJtior-trre

rGv

turbogeierators)ts'-61.

For

the

Fig.

3-e.

Jvnamoele"uic

*:llil'-"r?";t'*"Xiil;Jresuencv

a'c'

generator

and

schematic

diagram

of

a

dynamoelectric

exciter

with

a

high-frequency

a'c'

il;;"i;;-;d:;itd-siate

r.itifirr,

-"ee

Fig.

3-9'

The

rotor

of

the

high-frequencv

I

CEAPTER

TEN.EE

(3-3)

Accord.ing

to the

above=mentioned

facts

the field

discharge

time

has

its

minimum

*f,"o

the energy

accumulated

in

the rotor

winding

is

dissipated

at

EXCITATION

SYSfEMS AND AUTOMASIC

FDC

DE\4ICES

the maximum

rate

durin

rL^

uue eriod

^r,he

FDC

device aets. In this

case

95

-di

L+ Rti,:-Ur",

dt

(34)

the

generator

assures

additional

excitation

current

forcing

of

the m_ain

genera-

tor

6

due

to

a

free

current

arisiug

in

the

rotor circuit

in case

of

a short-circuit

at

the stator

side.

e

caused

by

free current

flou'ing

in

the

rnts

in

Lhe

EFC-Z

and

EFC-?

v'indings,

rrallel

rx'ith

aII

these w-inriings.

circuit

is

shown

in

the diagram of

llf-excitation.

The

rotor

current

is con-

[e

grid

control

device.

The

rotor

recejves

rups

of

the valve*s.

Under

normal

operating

per

eent)

is

from

rire

woiking

group

arid

the additionai

supply-

(30

to

40

per

cent),

from

the

forcing

group

of

valves-

In

case of

a short-iiriuli

in

the

generator stator

circuit,

the

forcing

group

beco-

mes fully

conductive

q'ith

a

resultant

increase

in

the rotor

current

to

its

per-

mitted

value.

?

q

Fi^l.l T.rica}'qrrra hv Tlainn Grid Arrfnmatie.

u-qJ.

I IElu

stsvusr6v

gJ

Devices

and

by

Changing

the

Field

Coil

Supply

to

Inverter

OPeration

Condittoru

for

tfu

qu.ickest

lield

disch.arge.

The

field

discharge

occurs

most

rrpiaf"o-*L"o

d"ti"g

tie entire-

field

dischirging

period, i.e.,

the

time

interval

when

the

current

iu"the

rotor

of

the s-vnchronouJmachine

varies

from

the initial

;;I",

lr-tl-rrt"[3-7],

the

stator

u'inding-

termina].

vol_tage

remains.constant

and

.q""1

td

ttre

maximum

value

p_ermitted

!i1 !he-insuJation

strength'

-'

L*t

the

value of

resistance'RL

in

the FDC

(Fig.

3-1)

be

far

above

the

value

of

rotor

*,inding

resistance

r. The

differential

equation

describing

the fieid

discharge

ptoce*i

in

such

a

device

is as

folloq's

L+*.R,i:

o

In

this

instance

time

where

U-r"

is

the voltage across

the terninals

of

the

rotor winding

in

the

excitation

forcing mode.

From equation

(34)

it

is

clear

that

the

best

field

discharge

conditions

in

accordance

vith

the

diagram

in

Fig. 3-1 are obtained when the

FDC

uses resistor

,R-I

v'hose resistance

varies

iuversely

to

the

current

-flow-

ing

through

it.

Expression

(3-4)

determines

the linear dependence

of

the

current

decrease

q'i.th

time

;- T

Umax

,

t-r0--r

o

tbe

current

falls

to

JTL

Lnrln:

I

o71-

u

max

which

is

t,he minimum

possibie

time.

Fi.eld

dischorge

with,_tfu

^atd

ol a

dci.on

grid.

For

the

Fig.

B-11.

Fieid

di-

scliematle

d14gram.see.Fig.

3-Il; fhrough,the

illai'j

cori-

s*fr".g,,

canrroi rvith

tacts

of circuit breaker

3

the

exciter

-I

supplies

power

to

deion

grid

the

field coil of

generator 2.

When the

FDC device

func-

tions,

main contacts

3

open first and

"uhen,

somew-hat }a'r,er, deion

contacis

4

break.

The

arc is

broken

in

the

crosswise

field of magnets

and

drawn into

deion

grid

5

tirat

breaks

the

arc

into small

portions

which

stream

until

the

^------r:- l:-ll ^-:l

r}

-l---^ 4^ -^--

OU.fl'eflt

IIl llelU V9LL

I' UIUP5

r,U ZBIU.

If

n

is

the

number of

grid

plates

and

Uo

is the

arc

voltase

b'etween

the

piates

(2,5

to

-30

volts

for

copper

plates),

then the

voltage

ae.ross

the

qrhole

arc

Uo:t{in

/a t\

\d-

|

,,

It

has been shown

experimentaliy

that this voltage

remains

constant

almost

within

the

entire

range

of current

variations.

The differential equation

describ-

ing the transient

process

is

as

foliows

-di

L;+riiU"-Uo

where

tr,

and

r

:

inductance and resistance

of the

excitation winding

Uo

:

exciter

voltage

until

the

field discharge

controi

starts

fun-

ctioning

The soiution

of eguation

(&8)

determines the current variations

with

time

i:+-+

{1-e-ttr1

(3-5)

zero

within

the

(&6)

(s-8)

(3-e)

Since

the

voltage

drop

across

the deion

grid

significantly

exceeds

the

vol-

tage

drop

across

the

rotor

winding

resistance

(&8)

may

be

simplified

without

t

CEAPTER

TEREE

ilil1||t!lrl

IrJ320

.r

1flilil|l||l

T .= 8fllA

The

structure

of

(3-11) is

the same

as

tirat of

(34).

It,

determines

the condi-

tions

under

w.]rich

the

minimum

possibie

time

of

field

discharge

may be

attai-

ned.

Therefore,

ti.

-iltla

discharfe

time

can

be

brought

close

.tt iF

ninimum

;il;-

#'pr"rrlrri'riroo.i"g

rhe

pErformance

characteristics

of

the

field

dischar-

eJ'it"i".'fuirrished

rvitir

a

deion

grid'

(3-10)

(3-11)

ilillfitl

Fig.

V14.

Field discharg€

control

unit

with

deion

grid

desigued

for beavy

currents

r

-

Bt8el

plate:

g

-

current

lnput

terminals;

t

-

main

movable

sontactS;

4.; auxiliary

ito"ali"-

finiabG:

s--

cross'tietd

extinglishilg

coiisl

6

:

g-9

.extinguisbing

borns;

z

-

deion

c"idj

s

-

eteel

*XL,rr;*?rTl

""8rffi

jrr"Gt"ot",-trero

corr;

rr

-

bvpa*s

7-2076

P

Q0['

Fig. 3-13.

Turbogenerator

fieid

discharging

I

-

23

lfw

witb short circuit;

lI

-

200 MW

under

normal

losd:

I

-

ercitation

current'

I

-

rotor'sllp

ring

voltage;

J

-

stator culTent

lo 101

.--1_-

CIIAPTER

TIIREE

YtusJ !J

Pqeo

itrstaDt

the arc

is extiDguished'-

,.,- - r,-r, -^-.-^r -^^ !.;-

r

'rhe

tlifferential

equatiol that describes

tbe

field

discharge process

rs

For

the sohemaiic

diagram of

the field di_scharge coDtrol see

Fig.

$15.

I

f"rriJs

to

aIIo*'

for

starting

by

the

self-slnchronizing

method

(see

Chapter

7).

Fi, e-{< l-nnfrnl

nf I'fl-C

rrnit frrrniqhed urif.h c dpinn srid

!

IE' V-^u'

vvuwrvr

.

o

-Eain

contect:

b-e-bloclrlngcontacts;1-4-contactors;

Er-^regulating rheostatl

h.

- power

limiting

r€sistor

cut

in

after

tbe

main

contact of

a

FDC

open6;_-4r

-

series

iiiistoi-;na

,--cdntactor

(these

are

installed

to allos

generator parallelling

b-r

the

self-synchronizing

metbod)

I

rll

Dr€vetrii[goveI}reatiDgandbur.ningoIthe-p!g!9g!qL4esistoIJ7whichpro.|c.ry.alcrectilje

fides by:fass

lor

the irldividual seitions

ol i@

--^ i- ^-+i---i.l"^,1

The

circuit

ernlloyed by

-the

FDC

with

deioD grid

etrvisag_es

inse ioD !l 8

|

,

in

rpsistance

ir

parallel

with

the ercitation wiadhg ol a

syachronous

macbiue

I

L

i+ir:

-A^^,

(3-L2)

EXCITATIO].i

SYSTEMS

AND

AUToTTATIC

FDc

DEvIcEs

If

the voltage

drop

across

the

resistance

of

the

rotor

as

compared

to

the

I't

E

Fig'

3-16.

Hydro-electric

gererator

field

discbarging

under

no-Ioad

conditjons

x-hel

using.-gps-discharg_e

tube.exeitatior (t:re-ge-reretor

re'!ing

is

i05

lvf$,')

voltage

value

U'r",

ma]'

be

neglected,

then (3-12)

takes the

form

L

+:

-

umax

(3-13)

ancl

becomes simiiar to (34)

which

i-s

the

condition decisive

for the

quiekest

fieid disc,barge.

Fiarrra 1-44 oh^tt,c o ftrniaol ^.^ill ^f +L^ +:^lJ J:-^L

e

rv ouvYrD

q

u-rlJrvqr

uDvrrru6adu

Lrr

LlLtt

IttrIu

uIDUIlaIg-c

Progess.

3-6. Conclusions

The

field discharge

circuit

must

enable

the

machi:re to

connect

by

the

self-

synchronizing

method.

.

4.

Pro*ising

is

the

dggign_

of exciters

s'ith

a

brushless excitation

system

as

it materially

improves

reliability.

.j*

\

s

\6

s

e

CHAPTER

T.HREE

r@*i

I

n,n€I?

1,/7

O^.o is-t\e

amplitude

valD6 of

.th€

ba.iBUE

vo.ltage

acmss the st{tor totmi-

;"""if,';$;;i";i;ii"i

it"iJ-ai"mge

timi.may

be

attaiDed.

I

r:frt' 105:+.4.6:4.48

g.

Usine

the data

of

the

foregoing

example.

calcuiate tbe

minimun

p_ossible

f^ie,l!;

discharge

ii6e

when

constant

voltaEe

equai

.to-ibe

value oJ tbe

test

voltagl, Ur"st: 3,500

""iii.

6urfG

maintained

across

the-rotor

winding

terminals

during

the

discharging

process.

Solution.

In

compliance

with

(3-6)

t

fmrn:10

#-

u

teet

lmtu:2,050ffi

is

about

o'5s

EXCITATION

SYSTE]YIS AND

AUTOMATIC

FDC

DEI/ICAS

10. Using

the data

given

in erample

3-9,

deterrlin-e

the fieid

is made

of

a

FnC

device

t'aving

a deion-grid

composed of

75

plates-

the

plates

be

equal

to

30

volts.

'solution

1.'We

first

determine

the

voltage

across

the arc

in

field

discharge

control

has

tripped

U

o:30'75:2,250Y

2.

a:rd

',hen

in

acccrdance

r.l'itl

($'11)

r

"'

"::

'rdltr

Li:

-(Uo-Uo):

-

(2

2i'0-345\

L

+:

_

1,905

tlt

bence

. ,

L

^^=^

0.806

n oc_

.

r:

I0Tf

I,uor,

-1105:u.ou

b

10.

What is

the

difference

between

tbe

thyristor

excitation systeznF

ind the

excitation

systems

utilizing

gas-discharge tubes?

11.

What

is

tirl-;;;;;;;ft

p"i""ipt.

of

tbe

brushless

ercitation

svstem?

12.

Wirat is

the

puipos.

oitfie forded

excitation

limiter

us€d

in

excitation

control

dev-

ices?

101

;;;i;-ggug;:l"Jrlti"dit":'J?i,,lit'il,'"til1;-"".

r1ri1c,g"'-r"-.Tr*:*

| ..,

:p--

v

=:t":z=#::'05

*rilgiiri'"'"ii*

1,1

a

las-discirarge,ture

oL

ltrvrj-lfrjxliter

-with

si'ultaneous

I

aDd

4.8

,_ ,^.

4.8

,

"

, , -

3'7.

Review

QuestiotrE

rn

of

synchronous

machines'.What

is

the dif-

ercitation

and

selt-excitation.

systems?.

h

various

excitation

systems

when

the

stator

: droops?

ge

ratdd

turbogenerators'.

- -.

lttiiliog

tLe

tiansfer

field

discbarge,qt?:::'

ntric,

gis-aischarge

tube

and

deion

grid

prtn-

ciples?

5.

what

are

the

cooditions

for

obtaining

tbe

minjmum

field

discbarge

time?

wbat

are

the

specific

feailres

encounrered

t;lH^ffrtr"rio"

or-"

lGia-aiscuarge

unit

using

deion

'ube

excitation

circuit's?

How

is

the

ercitation

curv-arc

t""iiii"i

forcing

group

is

available?

i.*ffii

;i

tbt

excitatidn

lircuit

wben

use

is

rlts.

tiioo

d"."tibing

tlie

field

discharge

prooess

rs

i

-

loe'Lllt|--'J

Here

L

ar:w=il4lr

For

tbe

erample

under

consideration

k:L:4

f

discharge

time

s'ben

use

Let

tle voltase

between

the deion

grid*

after the

and

L

_*

o.&9:4.8

,

;:':

T:16T-=

time

it

takes

to

complete

the

field

discharge

process

T

r

16

L:----

^7'

-

h-| 1

rr

where

the

Dotor

winding

curr€nt

i,

corresponds

to

the

residual

voltage

Ut"'

at

which

extinguishes

itself

i,

:

(Jr",

Is

V2

U*."

2.

The

Barzam A.B. Automation in Electrical Power Systems (Системная автоматика)

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