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

CEAPTER

?Tv'O

Regulation

may

be

to

astatic

independent

characteristics and,

statlc

depen-

dent

c-haraeteristics.

In case

of astatic

(floating)

regulation,

the system node

*^I+-^^ l,*' *'lrinh lho rornrlafinn ic nerfnrmad is tcnrcsentcd hv e straight line

v

\rrue6e

ryJ

n srvs

-I- ----'-'

-

J

parallel

to

the

s

axis

which

is

tbe

parameter

determining

the functionai

depen-

-J

-- - - f^- :-F+^h^^ *1-^ -a^a*it'a ^^m-nnanf nf f l"o cf of nl arrmanf I

(lguc!

fUL

IllD!alUfrgt

uIl9 lsavel

Ye

vvsPuussv

vr

uLe

eeqvvr

-

g.f

eOCt

Fig.

2-2.

Voltage

regulation

characteristics

(a)

astatic

(independent)

characteristic;

(b)

static

(dependent)

c'baracteristic

().-2\

Fig. 2-3.

Current

stabiiization

principle

Fig.

2-4.

Operation

of

generator-transformer

^^4^

^-.---^^r^J i.-a- ------,,, t t

DTTi

UUIIIIUULU(I

III LU

(.;UIITIUOO

I]USDATS

the.ryquired

phase

relationships

between the

voltages

and

currents

appliecl

to the AEC

sensing

sJ*stems

can

be obtained,

if the

-.-vstem-s

are

supplled

witU

voltages

as

follows

L,t:+t

:

J-9-

,*

tlo

nc

'

ri

-

L'nc

in

v

r2-

,r, -l

'"t

(Jrs:'u'n

-i"

r:.

",

Tl'st

where zc

and

fto

:

trans{ormation

ratios

of

the

mers

rsr

:

stabilization

resistance

AUTOMATIC

VOLTAGE

REGULATION

63

automatically follow

the

where s

:

required

static

Uno-t: busbar voitage

equation

Ue:Uno-t-f

g

reacrs

coefficient

with the generator

under

no-load

voltage

re-qtoration

or

ma-v

participate

in it

after

ths regulating

,capacit,y

of

the

first

ienerator

has

been

exhausted.

Thus,

reactive

}oads are

shared b-v

the

machi-

nes

sDontaneousl]'.

Wiien use i-q made

of

static resulating

cbaracteristics

(Fig

-

2-2b)

load.s are

distributed

between

the

machines

in compliance

with

the

characteristics

/g.r"ocr

determined

by

the static coefficients

si

:

tan

&1 drrd -cz:

tart

a"

reactive

slope

of

(z-1)

(2-3)

current

and voitage

transfor-

-- - 'r'

'-

CEAPTSR.

Tq/O

In

Fig. 2-2b

the

charaoteristic

slopes

are determined.

by

the

magnitude

3

n".

The

desired

sharing

of

.the-

reactive

load.s

amoDg

the

geuerators

is

oftaliulie

by

changing

this

naagnitudo.

ctrangrng

t-nrs

Eeagnltud.s.

with full-current

compoun{iug

devices,

the

static

'coatrol

U

s:

f

V

e.

,"oct)

is

obtained due

to

the

in'ternal st"atic

(steaay-s1;;;i-;";dr;i;;

;ftrhr'd"1;.in#l

U

:

Uno-t-U

l.'tts

1-14a

(2-4)

i'e',

with the

accepted

assumPtion-s

the

distribution

of

reactive

currents

is

inver-

sely' proportional

to

that

of ihe

reactances

of the

transformers.

Expressions

(2-G)

and

(2-z)

may

be

p.r.*orcJ

as

forlows

ALI?OMATIC

VOLTAGE

REGULATION

and

Hence

These

relationships

correspond

control

process.

U

u:

Urrnt

-

rttl

s,

,oo",

U

t:

a

ro-t

-

rtzf

E2

react

Ti- -Ti f

o'

h:

U

Etn-

l

slZnet

U

res:

U

sun

:

t]l

r-

j

*znet

to

the

steady-state

characteristics

of

the

b1'

adjusting

the

static

(stea

d1'-state)

characte-

(2-e)

(2-10)

The

redistribution

of

reactive

loads

is

obtained

coefficient,

u'hen

installing

AEC's

whicli

have

siatic

ristics.

The electromagnetic

voltage

conector

utilizing

the

circuit

shown

in

ensures

control according to

the

expression

The

voitage

stabilization

is dependent

on

the

amount

of

the

fuII

current

fiowing

in

the

stator

coils.

To change

the

static

eoefficient,

aD.

adjustable

resisior

r, i's

c'onnected

in

parallel

with the

winding

of

isolation

translorm

er

I

T

con-

nected

to

the

current traasformers

CT.

In controlled

pha-se

compoupding

devices (Fig.

1-10)

the

static

coefficient

isreguIatedbyvarvingthevalueofresistance},.

Th,e

gentrators

operate

i,nto

common

busbars

i,n sets

wi,th

power

traruslorrrlers.

Each

gener-ator

i_s

furnish,ed

wi.th'

AEC

dcutces.

Th,e speci.f

ted

ioltage

Leuel

mu,st

be

maintai,ned at

th'e.

collecting

busbars

(Fig.

24).

With

tire

system

schematically

shown

in Fig. 24 stable

sharing

of

reactive

ioads

b1'

the

glnerator-transformer

sets

is secured even

when

the

AEC

devices

connected

to

ihe

generators

output

maintain

their

voltage

astaticall5',

i.e.,

if

r'on

from

the

AEC

location

to

the point

ln

must be.

perfoli:rcl

is

iierroted

in"r

trument.

voitage

transformer

to

t,Iiilh

the

AEC sensing

eiemett

is

connected

is

designated

as un"n

and

the

current

flou'in

the

same

pirase

".

ir,,

then

this phase

volLage

at

tlie

receiving

side

is

ll-.:fi -...-f'f

.-.^nci

-87

"gZ-vno-t-

vvrrou

/q

r\

\L-o )

(2-6)

(2-7)

(2-11)

ln tq\

\L-tz)

By

neglecting

the

resistance

of

the generators

taking

into

account

the

active

component

of the

that

only

a

reactive

current

occurs, the value

of

to

the

voltage

phase

can be found

as

follows

r"'*o"'=ry:"

and

I

92t..,ct

-

uno'I-ub

xt2

where

rs1

and Etz

ate

reactances

of transformers

I

and

2.

From

the

above-mentioned

expressions

we

obtain

4:e

t

tz

xll

and

transfor-mer-"

and without

Ioad

current,

i.e.,

supposing

this

current

in

phase

similar

generator

and the

substation

busbars

the

2-3.

Group

Control

of

Generator

Excitation

s-2076

CEAPTEN

TWO

the

AEC

devices

in

due

time.

lvith

compound"ing

devices

having

a

voltage

correcror,

attendini

;;;"ffii

"h.og.

int

it"o*orhation

ratio

of

the

setting

Fig.2-5.Equaiizingreactive]oadsofsynchronousmachines

crpn in the. automation

of

a

voltage

regulation.pr.ocess

is

the

Ptt,of

"::l:l{

:-:d^: .^-r'.,11o" which eliminates

the

operator's

interventrgn

r+

lrte

oP€raLr{ru

L

iollows

its

specified

voltage

sched'ule'

w-ide

applicaiion

at

automated

multi-

cuble-free

operation

the

essential

requi-

control

devices

are

as

follows:

rctive

loads

as

prescribed

in

t'he

s-chedule

out

the

appearance

of

hunting

between

egulation

sYstem.

disconnecting

anl'

machine

from

the

egulation'

Wben

Cutomatically

discon-

rr"

must

be

automatically

disconnected

from

the

group

regulation

sYstem'

-

(c) Manual

-.;;;;;i';;

lil'

"*ottal_

volra.ge

controller

should

be

provided.

Group

regutaiion

devices

are

available

in

several

variants'

Schcmes

far

equalizing

reactntlooiibne

of

such

schemes

developed

in

the

soviet

union

is

lhown

in

Fig.

z-i.

-ru"

scheme

incrudes

d.c.

motors

-z

acting

i

t

Unt.n

AUTO}IATIC

VOLTAGE

REGULATION

67

upon

the

AEC

devices

of

the generators

through

actuator

units

Att.

The

number

of

motors

and actuator

units

is

the

same

a-q"the

number

of

g""rr"tors

sharing

the

reactive

loads"

The

fieid

circuits

of the

motors

are

connected

to

an

external

f,,l; ;"Xt

"T:

:1n; ::T :* :t ^::l^y:.":-

i s-.sup

p.I

i'

a *itt'

"u,""o

t

pro

p

o

r-

^vuvv^

vv

vvspvuesu (,r

Llr'

DtULUI'

Gu.rrgnL.

Used in

the

reactive

load equaiizing

device

in place

of

the

reactive

co'po-

nent

of

the

stator

current

is

the

rotor

current

proportional

to-i[is

current

or

Dusoars

of vcttage

ceniral

canirol(er

Fig.

2-6.

Grgup_ excitation

controi

n,ith

equa-

Iizing

reactive

loads

and

central

voitage

con-

trol I er

CC

-

central voltage

controller;

LDU

_

)oad

dis_

tri_b_utron

unit;

OAU

-

output

amplifiers

unrr:

Err'c

-

exclter

T.Sg"_l,..rd_:gil;

M

-_

resutatins

r uvu-ra

I

luu

Lul

Fig.

2-7.

Group

excitatjon

control

q,ith

-.q

-

a centrai

voitage

controller

-!-C

-

cenL-3]

voltage_c-ontroller

(corrector):

M

_

power

ampllf ler:

-E,4.FC

_.exciler

.auxiliarf-

]leld

coil;

EFC

-

exciter

field coii

'

ATTTOJ\IA?IC

.I"OLTAG

g

REGULATION

69

68

CEAPTEN

T.wO

by

the output

amplifier

unit O,4

U. an_d

acts

upon

-the

change

in

the

excitation

of

the

generators.-The

excitation

(field)

is

controlled

by

means

of

the

motors

operatiig

the

regulating

rheostats

of

the exciters

or

b-v operating

the adju-stment'

device-" Jt tne

individual

eiectromagnetic

voltage correctors.

Such a

system of

Fig' 2-8'

*"ou

o",ii"i'T:""il"f;';'"i,,ffi

l,

"Nt

:1

'l, ;;H1L,I!

t'u*' co n

tro'er

control

(regulation)

equalizes

the

reactive

ioads

in an

.aperiodic

manner, 30

;;10

*

Iftl"r

Jhe

reacfive

power

distribut.ion

between

the machines

has been

disturbed

to

+-30

per cent

of

the

power

rating of

the

generators.

-

--l

Group

regulation

sch,emc

with

a

central

controllcr-

Reactiue

Load balarue

between

naralleled.

g-encrators

i.s obtai.ned

by

using

generators wtth

similar

etternal

ch'arar-

irriiit.

Tire

scheme

means

replacing

the

individual

voltage-

correctors

with

*

""**o"

one

(Fig. 2-7)Iz-81.

The

output

current

_of

tire central

controller

(CC)

corrector

is inoreaJed

by

the

magnetic-amplifiers

MA

and feeds

into

the exciter

,"iiri"ry

iield coil

EAFC.

The

siheme

is

simple

and

contains

no

ncovable

parts,

but calls

for similar. adjustment

of

the

external

characteristics

of

the

genera-

tors,

otherwise,

the difference between

the

reactive

loads

of the generatois

may

be significant causing

underloaded

and

overloaded

machines.

-

Group

co-ntrol

scheme

u;ith' a

central

controller

and.

a dnuice

lor

distributing

reafiive loads

agairut prescribed

sch,edule. For

tbe

biook

diagram

of tbe

device see

Fig. 2-8. This device

Eas

deveioped

b:v A.

tr{oskalev

and

ofhers

of

the

Ail-Union

Poq'er Engineering and Electrification

Scientific

Research

Institute.

-

The

voltage- value

-requireti

at a

given

point

of

the

pou:er

system

is

set

by

voltage

controller

I.

The

value

of the set

voltage

can

be

cbrrectedeither

automa--

:^'::,i^;L:':i_:::.:':;";;^^-:"i::^i:_":".::,-'_"^_v"_*:', l::."i""ruers'

ur

arrEr ''Ie

rcEurd.urrrS

L,dp.rL.r[.!

Ui

r,uE

gt,rttrtdLUr'] UaS

ljue11

e)rI]aUSIgO.

2-4.

Automatic Devices

for

Changing

the

Transformation

Ratio

of Power

Transformers

Automatic changes

in

the

t.ransformation

ratio

of

power

transformers

are

undertaken so that

cotrsurner

voltage

may be

maintained at

a

certain

ievel.

The

transformation

ratio regulation

by

tap

changing

is

accomplished

in a step-

like manner.

Continuous control

of the

transformation

ratio-through

changis

/U

CEAPTER T'WO

in the

magnetic

state

of

the

magnetic circuit

b-v

magnetizing

it

is

sometimes

used

for

low

rated trausformers intended

to

handie

special loads.

_

When-designing

the sensing element

of

the reguiator

step-like

changes

in

f ho trondfnnmof inn nqf in ^{ ^rtlinor-' hnntol lronc{ar*^-.

"*,1^-

I^^ J *--^r L^

'vru^!qr

!t lru

?vv!

!rsl'DrvluErJ

t

tltrsl rudu

ll_lust

Irg

taken

into account.

The regulator

must

have a

dead zone

which

overlaps

the

vcltage

overiegulation

value

afier the reguLating

deviee

is switched

tirroueh

one

step.

Reguiation must

be

slow in

order to

prevent

the

switching

device

from

o-perating during

sbort-time

voltage

variations

as

frequent

operation

m.ay damage

the

mechanism. The

output

control

signal

is

usually executed

within

20 to

30i.

The

sensing eJement of

thp

regulator

can respond

to a

change

in

the voltage

at

the reguLator location,-

to

a change in

the value

of the

vector

voltage

sum

ai

the

regulator

position

q'ith

a_

voltage

drop

because

of a

current flow

in

an

equiva-

Ient resistot, i.e., to

a

cha_nge in

-the

voltage

at

a

certain point

in the power

srrstem electricaliy

ciose

either

to

the load-centre

substation

or to the

connection

point

of

the

current

teceivers, and

to

a

change in the

vaiue

of the voltage

at the

reguiator

position s'ith

a comection

by

the

value

of

the

current

fiow

in

the

feeding line or by

tbe

value

of

reactive

power.

To

control

the transformation

ratio,

when

under

load,

the

transformer

tap-

changer

position

is sometimes

changed aiso

aufomatically

b-v

a

programmbr

insfalied at

the substation

or

at the

operator's point,

to

follow

an hour

sihedule.

for inslance.

When a

trausforner

with autorr.ratic

coniroi

of the

transformation

ratio is

installed

at

the recsiving

consumer

substation,

it is

better

to

accomplish

the

voltage

regulation

together

with

the

correction

of the

current

flowing

in

the

feed line or the

value

of

reactive power.

If

such

correction

is

not

used,

then,

tending to

maintain

a consLant

voltage

across the

consumer

terminals

in case

of

a drop-in the

voltage

due to increased

losses

when

the

load gro\I,s,

the regula-

tor

switches

over

tbe regulating

device

of

the

power

transformer

in

order

to

rcdrre.e the transformation rat.io.

The

result

v.'ili

be

an lncre*se

in

the

currenr,

fln'rxrino f hr^ttoh +ho foorl li-o o-d o rlrli*innol l^oooo -,i+1. *"-+1-^- -^1.,^+: ^* ^!

vs^vu6u uusrervuqr

tvoovD wruu

lua bugl

ltt(luul,lull

ul

the voltags

across

the

terminals

of

the power

transformer.

,A.Iong

with

the

principle

of

reguiating

the

voltage

by following

its

devia-

the regulating

principle,

the_

control

system

must

maintain

the

voltage

within

the limits

permitted

by

the

load of the

power

system

region.

, Let the voltage

regulator

priucipie

be

studied

on the

basis of the

TsSRZAI

type

(I{CPBAH)

regulator known for

its

simp}e

construction

(Fig.

2-9).

The

controlrela-vs

lCR

asd,2CR

co^nt1oi

tb-e

tap

changer

of the power

trans-

former

b.-;i means.of

auxiliary

relays

TAR

and

4iR

andtime

relaf

iTR.

fbe

relav

coils

are fed with

a.c. power.-Relays

lCR

and 2CR

are two-co'it

polarirea

(b)

ror

,.u,-"lr"e;,?;?;J1iT:Hfftil"":,,:,T,T::,t

!!,

^ u ,",

relays

(tbe

coils are

in

opposition).

Under

normal

cond.itions

the

resultant

emf

of

_the

rela-v

armature

is equal

t_o zero

and

its

contacts

are

opened.

One of the

coilsof

r-elays

lCR

and

also

of 2CR

are connected

through

r*ititirtr

to the

ter-

minals

of

the

instrument_voltage_transformer

VT

in series

with

tbe windinj

ot

a

guickly^

saturable

transformer

^S?.

Depending

upon

the value

of

terminai

vol-

Lagg

U

of

the

instrument

transformer

VT,

the-current,.L,

flowlnt

in

one of

the

goilj.of

relays

/Cr?

and

of.2CR

has

a

clearly

nonlinear

Lharacteristic

(curve

-l

in

Fig. 2-9b).

The

other

coils

of reiays-fCfi

and 2CR

arc

oonnected

to

the

second,ary

cir-

cuits of tbe

voltage

transformer

ST

and the

intervening

transforme{

ICT

AUTOMATIC

VOLTAGE

REGULATION

7t

lo)

79 CIIAPTER T\\'O

(Fig.

2-9a). The

primary

of

the transformer ICI'is

connected

to

the

secondary

winding

circuit

of the crurent

translormer

CT.

The behaviour of

the

current.I,

flowing

in the other

coils

of relays

lCR

and

2CR

conlorms

to

cutve

2

in Fig. 2-9b.

The

settings are

adjusted

by means of a

series

resistor and tap

changing on

the intervening

transformers

so that at

the voltage

equal

to

the

set

voltage.

the

currents

,I, and

.I,

equal each

other, Departure

of the

voltage

from the

specified

value

causes

relavs

/C,R

and

2CR ta function.

llorp

Fig. 2-10.

Voltage

regulator

circuit

using

tunnel

diodes

On

the suggestion

of

engineer

Ya. Barkan, the Riga

factory

"Latvenergo"

manufaetures

power transformer automatic transformation ratio

control

units,

ltype

BAURPN-2

(EAVPIIH-2)]

for

transformers furnished

with

on-Ioad

mans-

formation ratio control.

The

device is transistorized.

The

measuring

eiement

utilizes

tunnel

diodes. For the

block diagram iliustrating the operating

principle,

see Fig. 2-L0. A

specific feature of

the tunnel

diode

is that it has a low

resistance

only

at

a

certain

value

and

polarity

of

the

applied

voltage

(Fig.

2-11). This

gives the diode a

valve property,

i.e.,

use

is made of a

tunneling effect which

arises

after the applied

bias

has

reached the

magnitude and

polarity

at

which

the

diode beeomes conductive.

AUTOI\TA?IC

VOLTAGE

REGULATION

The

voltage regulator includes a

measuring

element,

a curreDt

cornDeDsa-

tion device,

time dela;*

elements

and

an

actuator.

The

setting is

adjusted

by

varyiug

the

resistance

of resistor

-Ro..

connected

on

the

primary side

of

the intervening transformer

72.

The

minimum

vaiue

of

the

voitage setting is 90

volts

and the

maximum

110 volts.

The

settins,

can be

(")

(b)

Fig. 2-11.

Principle

of operation

of

tunnel

diode

(o)

Uiggering circuit;

(b)

tunnel

diode

characteristic,

J:

t(Lr)

adjusted

continuousl-v

in

the

range of 95 to

105

volts.

Tire

inert zone

isadiustable

w-ithin

-1

to 6_

per cent of the setting voltage

with

the

aid

of

the

resist,or

,R".

r.

Taken from this resist.or

by

means

of

its slide

is the

voltage

fed

via

resistor-Ez

to the

transistor

QZ

af. the

MORE

channbl.

The transistor

Q-Z

of

the

LESS

chan-

nel

is connected

to

tlie

tapping

of

the secondar5.

v'inding

of

transformer

Tt.

Fig. 2-12.

Osciliogram

of

tunnel

diode

puises

In

everv other period

of alternating culrent. t'iren

the

current

amplitude

o.'^on.lo +1"^ ^-^-^+i-^ ^.'--^*+ f ^t +].^ +,-**^1:-- l:^l^ aL^ I-r---:- ?r. - r

;:J^""-i:.'1,'-'!-"j1:':q

":":,",\'g? "'

trfv. tru'rru"1'l',H

lttt"',

t1"

aoLteI'

rs

rrlppeo

kt

:0.2),

us-e

is

mads

of

capacitors

CI

and.

C2.

The discharge

time of the

capa-

citors is

overlapped by the on-off time

of

the pulses

shaped

by

the tuunel

dioiies

TD-[ and TD-z.

The

interrupted

operation of tunnel diodes provides

a reset,ting

ratio

of t

for tbe

whole

device, since

the repeated

functioning

of

the

tunnel

diode

is

possible

only

when

the amplitude

of

the

current

in t.he

circuit'again

exceeds

the

operating current

(voltage).

-

Transformer

Tl_and resistor.R'

compensate for

the

voltage

drop in the

power

transmission

line between the substation

where the

regulator

is

instalJed

and

"t

Sup.oty:rrcuil

rlJ

C nnl ninttil

.-L-

F.

l+

I

Supplt

T-

I+

!:

-t--

lA,

,2

l.

CTIA?TER T.wO

the

consumer

where

the specified

voltage

is to

be

maintained.

When the

cur-

rent flows ooly in the

primar*v v'inding

of transformer

Ti,,

tbe

i-nternal

shift

angle of

the

current

flowing in

the

secondary

winding

amounts

to 26-30

deg,

this

rietermiaes

^r,he

eounec'r,ion

of

tbe

primarv

-windins

of the

trausformer

Ti t,o the

current

transformer of the lagging

phase.

The

time

deiay

elemeui

made of semiconductor elements

can

provide

con-

tinuous adjustment

for

7

Lo

2 min. Fig. 2-10

shows two time

delay elements

Fig. 2-13.

Voltage

regulatoi circuit with two time

delay

eiements

based on

tunnel

diodes

D ^-J Zr *L:^L

.:-l^-^-J^*+

^-^-^+:*- +:-*^^ 4^- +L^ T [iOC ^-l trr/1Dr}

Itl dlt|.I 12772

vrLLLrtLt

uu.Sl,lltt

rj.tUtrPt;lurrlt, UPt;ra1LIJ.IH

U.tI.Lrt s IUI t,LlE trI]lJLl

anU

IYIL,r-ftEl

cbanneis. The ouiput,

signai

of

ihese

channeis

is reaiized

with

the

aid

of

reiays

R-l

and

R-2.

Operation

of

the relay

l?-/

nakes

the

tap

changer of the controlled

transformer

increase the input

voltage

of the

voltage

regulator

above

its dead

zoue,

s'hile

the

operation of

the relay

.E-2

causes it

to decrease this

voltage

belor*'the

dead

zone.

The

reguiator may

utiiize

oniy one common

'uime

cieiay

element.

Iiowever, if

this is

the

case,

there

will

be

no

possibility

of separately reguiating

the

opera-

tion

time

of

the

LESS

and

h{ORE channels.

When the relay

,R-.2

functions, the

circuit of

the relay .R-2 opens

to

prevent

their

simultaneous functioning

in

case

the inert zones

of

the

channels

overlap

each

other.

For a complete

schematie diagram of the

pulse

voltage regulator

employing

tunnel

diodes see

Fig.

2-73. According

to the

description conpiled

by

the

desig-

ner,

Ya. Barkant2-z1,

the

operation

of the

regulator

is as

folloysfr-a].

The

lower

channel makes

the

voltage

decrease.

In

the

shrting

(initial)

position

the transistor

p'l

is cut off, while

the

transistors

Q'2

and

Q'4

arc

F

AUTOMATIC

VOLTAGE

NEGULATION

conducting. The

trausistor

Q'4

bypasses

the

capacitor

C'5

of.

the

tine delay

element

and

feeds the cutoff

potential

to

the

base

of the

transistor

Q'5.

The

result

is

that the

flip-flop

is in the starting

positiou.

The transistor

Q'6

is

cutoff

^- .] aL- -^]^-- T>O :^ l^^-^--:-^l mL^ ----^- ^L--*^1 l--- -^r t----!: -- :- aL^

auu

Llle fulily

flp

rs

uttruclgrzEu.

rlu

upPvl u!.a!.l.Iur

uueD uu! rrriloLIUrII ru Luc

initial

position either.

In this channel

tbe simiiar

state is

provided

when

pulses

are

fed

to the

t,unnel

diode.

The firsi; iransisior

periodicaily

becomes

conduciive.

The

pulses

are

'tectified"

by t,he

capacitor

C3.

The

transistor

QP

becomes

cut

off.

After

the capacitor C4

has

discharged,

the

transistor

Q4

also

stops

conduct-

ing.

The

cutoff

pulse

is temoved from

the flip-fiop

and

capacitor

C5 charges.

AJter it is charged

to the

potential

applied

to the emitter

of

transistor

Q5,

the

diode

Di

is

ready to start

conducting. The

in

sequence

from

the on-off

wave

generator

(avalanche

diode

D2

and capaeitor

C2) is

fed

through

the

diode

and flips

the flip-flop.

The

time deiay fiip-flop utilizes

transistors

of distinct

types which

are

in simiiar

states.

When

flipped, both

of

the

transistors are

triggered

iato conduct,ion

and tbe relay functions

The

same happens

to the

other channei

'when

the

pulses

disappear

from

the

tunnel

diodes. The discharge

resisLor

RLl

ma-v be

small

in

rating.

In this

case

the voitage

retwn

to the dead zone

canceis

the time

delal'. Repeated

operation

of

the

regulator involves almost

full time dela-v.

When

tbe discharge

resistance

is

commensurate

with the

charging

resistance

R[Z,the

time delaf

is not can-

celed at once

when

the voitage returns

to

the

dead zoae.

Repeated

operation

of

the

measuring

element

will

make

the reguiator

operate with

a snaLler

time

deiav. In

',.his

case the

tirre

deiay acc.umulat.es.

'

The

divider is fed from the transformer PT

through

a rectifier bridge. The

capacitor

C-I

serves

as a filter.

The

power

consumption is

0.5 VA

for the

measur-

ing element and 2

VA

for

the

divider.

2-5.

Deviee*"

for Automatie Capaeitv

Control

of Capaeitor Banks

\X7L^- -^-^^:!-- L^-f-- ,] -r rL^ --.L^r^a:^- ^- J -r

rL^

l^^ l- ---r--^4i^

vYttvu

(ialjauruul'lraul{'D

a1ru {rStiu

au

Lutr

suusLaLruu auu

aL

Lutr

luilub,

auLUrrrilurL;

voltage reguiation is attainable.by

switching

on

or

ofJ the

capacit-v of the capa-

citor banks,

depending upotr the

voltage

across

the

term.inals of the sensing

element

or

upon the

value

and

polarity

of tbe reactive pov'er

passed

over

the

feed

line,

or upon the current

flowing in this line.

Often

the

capacitv of

the

bank is switched

on

or off

due to

a

combined

effect,

of all

or

some

of

the above-

ment,ioned factors. The control of

the

eapacii,or banks

may

be also

from.

a

pro-

grammer

device,

the

simpiest

case

being,

for

example,

an electricai contact-

type

clock.

Availabie

from the

Riga

faciory,

"Latvenergo" are

transistorized

devices,

type

ARKOH

(APKOH;tz-s:t, which

are used

to

control

capacitor

banks. The

regulator provides

for

voltage regulation

with a correctiou

as

to the

cu.rrent

and

the phase

angle between

tbe

current and

voltage.

The

regulator incorporates

a

controller

and 10 actuator

units.

Let us consider the operating

principle

of

the

device

controliing

capacitor

banks from the

relaying

circuit shown schematicali5'

ls Fig. 2-74.

JJ

+

AUTOJ\{ATIC

TOLTAGE REGULATION

The

power

supply

to the

oontrol

circuits

and the

automatic control devices

is

from a

potential translormer conDected

to the

substation

busbars.

The

device

can operate

either

on

the operating

current or on

a rectified

curreut from

a

supply

unit.

Fig. 2-14

iliusfrates

the

r,ariant with the use

of

rectified

current.

Used

as

the

sensing

element

is a

voltage relay with

one

front

contact and

one back

contact.

U/ith

the switch opened.

the

resistor

15fi,

is short-circuited

by

the

auxiliary

contact of

the su'itch and

relal'

6VR

rcceives tbe

interphase

voltage

Uob. If.

this voltage is iess

than.the reset

voltage

of

relal'

6VR

(Ur.roy<-

U,)

tine

6VR-2 contact

is closed. The

time

relay 7TR is

closed and

after the

specified

time

period

it sends

a signal

to turn

on

the capacitor

bank.

The signai is

fed

througir

the

making

(frout)

coutact

4AR-2.

A-fter

the

hank

has been

turned

on,

the busbar

voltage

of

the

substation.

as

a rule

grows.

To

prevent the bank

from

immediate disconrrection,

the

operating

setting of

relal' 6trlft is automaticali-v changed

by connecting serie*q resistance

15R,

in series

*-ith its

coil. In

this

case relay 6P-R

operates onll'when the

vol-

tage

grows

in excess

of

the

increased

operating

setting.

The

capacitor bar:k

is

disconnected

after the operating

time of

rela-v 8fR

has

elapsed.

The

operating

time

of

reiays 7TR and

8?R

lies

u'ithin

20

to

30

s to

prevent

superflous

switching

operations

in

case of short-time

voitage

variations.

The

resistors

l6-R, and

17ft,

ensure

the

thermal

stability of the

coils

of

rela-vs

7?F and

8f,R.

These

resist.ors

are connected instantaneousl3' |1' 15.

time reia-v contact aJter the

solenoirl

llungers

ol the

actuators of

tLrese

relavs

have

retract€d.

In

the

picked

up

state the

current

fiorl

in

tiie

relas is

Jess

than

the

pick-up

current and

somen'hat

above the

reset

current. The number

of

on-off

switchings is

re.corded

b5' counters 9 and

70.

Srvitch

/2

is used to change

over

to the

manua]

or automatic

control mode.

The

manual control is

effectJd

through the

control

switch

(11C5).

The

protective

rela,ving of the

capacilor

bank

guards

it against

interphase

faults

and overloads

b1'means

of cument

rellvs.l s'hich are inverse time

lag

devices

with

a definite m,inimum. A

current

cutoff

rrrovided

in

the relai' func-

tions in case of a

phase-to-phase

fault.

In addition.

the circuits

of capacitor

banks ranging from

6

to 10

k\z are

furnished with a fuse. Relal'

2 protects

the

banks

against

earth

faults.

Signai

relays

3

monitor

the

operation of

the

protective

relaying s)'stem.

When the

protective

relaying

system functions.

rela-v 4

opens

the turning-on

circuit of

the

switch

to prevent

automatic sv'itching-on of

the

bank

at

fault

by

the

contact

of rela1.' 7TR. The rela-v

(4AR)

is of

tbe self-retaining

type.

Tlie

circuit is

reestablished

by

operating

push-button

5 u'hich opens

the

self-retain-

ing

circuit. The frrnctioning

state

of

relay

4AR

is

monitored. To

disconnect

the

automatic control circuits,

use is

made

of

jumpers

13

ard 14.

When

placing

capacitor

banks

into

service,

provision

should he made

for

their

forced operation,

i.e.,

for a heavy

rise in

the

network

capacitance

when

the

voltage

drops

below 85

per

cent

the

rating. This is

because

the

effect

of

the

static

compensators decreases

with

a decrease

in

the voltage.

As

i1

TU

It\:-

-tc

(2-r3)

Fig.

2-14.

Capacitor bank control

circuit

diagram

78

CEAPTER

:rWO

tbe

currenL

f

"

decreases proportionaliy

when the

volta

ge

[]

drops

with inva-

riant

u

s,

which

causes

additional

reactive

losses

and

a

filrther

drop

in

the

vol-

tage,

i.e., the

process

attains

an avalanohe

character.

This voltage

drop

c.an

be

A

R

L

stopped

b,w an

abrupt

drop

of

theeg

value,

i.e.,

by

an abrupt

insrease

in the

current

-Is

and

reduction

of

the

reactive

losses.

A-u

increase

in

the

capacitance

current

is

attai-

nabie

by

switching

on

additional

capacitor

banks

o-r

by switching

over the

capacitors,

ls

per

scheme

shown

-in

Fig.

2-15,

from

the

interphaje

voltage,

when the phase

current

is

,

BUpn

r;

J

e:

-;--

:

1.5

-

Pn

-

acc

EC

to

the phase

voltage,

when the

phase

current

be-

comes

equal

to

,

Uph

nUph

-. _:

:

_

-

v

0.529 rg

(2-1s)

This sn'itching

operation

is

effected

throueh

switch

2.

2-6.

Voltage

Regulation

by Booster

Translonners

DiagraTs

showing the

regulating process

are gi-

ven

in

Fig.

2-16.

The secondarS'winding

of the

boosler

may

be connected

directly

into the

transmission

]ine or in

series

with

the

windings

of the power

transformer

(near

the

terminals

on the

neutra]

2-15..Forcing

of capa-

point

side

of

the

power

transformer).

The

primary

cir.or

bank

of

the

booster transformer

is fed

from

B'r-o

iO_kt

busbars

througb

an

auxiliar5.

variable-ratio

transformer.

RezuIation

is

either vector-coincident

or

composite, depending

on u'hether

tne

vector

of

the

specified

voltage

coincides

$'ith

or

is

shifted relative

to

'that

of

the

voltage

being controlled

(Fig.

2-16c). In

the

latter case,

not

oniy

is

the

voltage

changed

in

its

value,

but

it

undergoes a

phase

shift

too.

Tiris makes

the

so-called phase-shift

regulatiou

[obtainable,

wbich

can

be

used to

elimi-

nate

excessive power

losses arising due to

some

nonuniformity

of

parallel

transmission

lines.

The

transformation

ratio control mechanism

of the

auxiliarv

transformer

is adjusted

either manually

or automatically.

\roltage

Regulation

by

Changing

Excitation

of Synchronous

Capaeitor

The busbar

voltage

of

the

receiving

substation

can

be

regulated

within

certail

limits

by

varying the

excitation

mode

of

the

synchronous

capacitor

installed at

the

receiving

zubstation

and

by

providing

operating

conditions with

Ieading

or lagging

current.

(2-14)

tsJ

(')

Fig.

2-17. Voltage

regulation

by

changing

tor and

power

current in synchronous

capaci-

factor

(c)

Fig.2-16.

Connection of

booster transformer

(s)

in

B€rie6

witb

power

trarmiesion line;

(b)

eane

with

power

bansformer

wlnding;

(c)

vol-

ra€B regulation

principle

(d)

(a)

supply circuttl

(H)

vector diagrame

:E0

CEAPTER.

T.wO

2-8.

Yoltage

Regulation

by

Controlled

Reaetors

Lnput.<

|

6

reaciance

of

the

reactoi

automatica_

y

A .-.

Ih'

.and.

abruptly.

rises

,ua,

li-'tn,

Fq

s

f\ ::i:::l

':,::iti-1,"1

iHg

si,ort-circuit

I f

nln_"_F_.

* ::;-.-"^"uj-urrEu

ulle

,bltorf,-Cttoutt

CUnent

---i

giI",.H:

'l..:l""X'.*ili"'l1i.i:ffillffJ;

2-9.

Conelusions

AIIfOId.f,TIC

VOLTAGE

RE&I'LArION

/t

Rvcfornc for rrrnrr- avnifo*i^-

--

vrt

vavl

uq

vlvu

personnel

who control

the

operation

-^^,,1-+{^- ^c ^^-

rsSuraLrul-r

ul

Et

utsrauul__\

gasg

[I}e

woIK

oI

of.

poi*'er

units,

making

it

possibie

to

ope-

rate

the

generators

of

a

multiunit

power

station

as

one

composite

generating

uo"it.

ie

voltage

in

high_tension

networks

is

rs,

the

inductive

reactance

of

wlrich

is

3netizing

current.

ctified.

alteraaiing

curreut.

If

this

cur_

lr

connect,ed

to

the

busbars

of

the

power

receiver.

tiien

a

short_circuit

makes

frcm other

the

busbar

^

voitage

d.rop

to

zero,

tire

8t

component

of the

load

curuent

can

be

cr

"1.'MaiutorlrBoei'of

tbe

voltage

rated

level

at power

s-I,s1.em

nodes

and

-j".r.

ruarsesrrd.uuril

ur

r.j_lLi

vurr,argc

rat,{ru

!eveI

ai

pOWeI

5-'115.l,€11L

nOdgS

and

at

consumer

points

is an important

indication

of

the

generated

Dower's orralitr,.

ra

ll--ry

(sw[,ch)'

-l

'. .

-

?he

controlied

reactor

can

be

used

I _ l

ne

conrrolled

reactor

can

be

used

|

lc

lood

to

change

the

value

of

the

capacitance

r

current

in the

line

due

to

a

iapacitor

L^*I- ^--l r r .,

ator

usinc'

Fig.

2-18.

Autornatic

vo-ltage

regulator

using

a

controlled

reactor

J

-

controlled

reactor

(choke

wjth

superposeC

mag-

netization);

?

-

rectitier

device;

.?

_

f dnk

cl

i;;;;-'

4:'

:-t-*i,tiii#.;

r

.-

automau"

"ifrl?i

re8ulator;

6

-

auxiliery

inputs

to

-regutaior

b-e

used to

perform

phase-shift

rezuIatior

the

transmission

lines.

An

advantage

r

absence

of

switching

devices

to

peifor

6-2A7 6

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

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