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

T

t

,i\):

CH.APTER

Tl,\'EL\'E

in the

method

described above,

the

protection

is

presented b:' a current

cutoff

or

single-stage

distance

protection.

Now consider the

operation

of

the

protection

and

automatic

reclosirtg

when

faults oecur

within

the reach of

the

instantaneous

proteot.ions of

two

adjacent

seclions

(section

11.

section III

at

point.

SCr,

for instance).

If

a short

circuit

occurs

at

point

SC,

both

sections disconnect

in

one

operation.

Section

,i.I.i

rn'liich

is

closer

t'o

the

po\^rer

source

is reclosed b1'

the

ARC

device

u'ithin a shor-

ter

time.

As

this

happens. the

nonselective

protection from

the

side

of

the

suppl_,r

subst.ation

s'rill remains closed for

some

time.

If

the

insulation

of

sec-

tton III

is

reestablished

during

the deenergized

state

of

the line,

the line

remains

Fig

{ 2-4

*"n

u

l?li"l,",i

;:x' :::i;:.,H:'

ff

:i:l Ji"# ;,#l1

li""

d

u rr n

g

sequ en-

colrnected.

Next. the

ARC

device in

section ,I/ operates.

The

time taken bf it

to ciose

the

breaker is

gre.at.er than

the

total time

taken

to

close

the

breaker

of

t,he

ARC device

iocated in

section ItrI

and

the

time

of

subsequent

tripping

of

the

breaker

if it

is

connected

to a

persisting short circuit-

At

t,he

moment

the

breaker

is closed

bl'

the

ARC

device of

the more

remot,e

section ,I/.

the ,qelective

protection of

the

nearer

section III

is

automaticalil'

OPERATION

OF ANC AND ATS DRI'ICES

WITII

NELAYIT.IG

of

time

rela-v Z.R

which holds

itself by

an instaotaneous contact.

A

little

later

after

the

breaker is closed

the

sliding

contact

completes

the

circuit

of

the

auxi-

Iiar5,'-relay

AR. The

rela;.'l..R

opens the nonselective

protection

circuit

before

[he last-to-operate

contact of relay

?.R closes. The

time

settinp

of the sequen-

tial

automatic reclosure devices is intimated

from

the

example

given

belos'.

Let the

circuii

(Fig.

12-3) be

furnished

q'ith

a

sequential"automatic

reclosure

device.

We

choosei

,

(a)

Tbe time needed

bv

the

ARC

device

to

close

the

breakers.

tbt

fhe time for

discoiinection

of

the

nonseiective

orotection.

(c)

The

time

required to

reset

the

device

element

disconnecting the

ronselective

protec-

tion,

say,

for

section

,I1l.

Being

given

tbe

operating time

of the ARC device

in section

III

as

equal

to I s.

Dis-

connection

of the nonselective

protection

of section III is

carried

out

after

the closure

of

the sliding contact

of

relal'

?-.R

(Fig.

12-4). This

time is

0.8+ 0.1+0.{s+0.3: {.3.5

s

\47here

0.6 is the

breaker

ciosing time, 0.1 s

is

the operating time

of

the

nonselective

protection,

0.15 s is the breaker

tripping'r,ime, and

0.3 s

is the

margin

time.

The

operating

time

of

tbe AR

C device in section 1.I

is selected so that the ciosure

of breaker

.I.I

takes

place

after tbe nonselective

protection

in section

III

is

disconnected

i.e.ncr:

1+ 1.35+0.3:

2.65 s

wbere

1

s is the

operating

time

of

the ARC

device of section III,

1.35

s

-

the

closing time

of

the

sliding

coDtact

of

,rela1,

TR

of the circuit shown in Fig.

12-4, and

0.3

s

-

a

margin

tirne

(additional

margin

time results

{rom

the

fact

tbat the contacts

of

the breaker

make

0.6

to

0.8 s after

the

operation of

the ARC

device

in

section.l.f),

The operating

time

of

the

final making contact of

relav

TR

in

section III is determined

from

the

fact

that the

nonselective

protection

of section

III

can

be reestablisbed oniy

after

tbe

ARC device has

closed section 1,I which is

tripped again

b1'the nonselective

protectjon

in tbe case of a

persisting

fault.

The

making time

of

the last-to-operate contact of rela."*

TR of

section

III is

(2.65-

1)+0.8+ 0.1+0.15+0.5: 3.2 s

wbere

2.65

s is

the

operating

time of

the

ARC device of section

II,7

s

--

tbe

operating time

of

theARCdeviceof section

III,0.8

s-theclosingtimeof thebreakerof section,I.I.0.1s-

the

operating

time

of the

nonselective

protection

of

section

11,0.15

s

-

the tripping

time

of the

breaker

of

section

.f.I,

and 0.5

s

-

a margin

tiuie.

same.

As

compared

to

the method used

to correct noDselec,tive action

of

the pro-

tection

with

the aid of

ARC

devices with increasing the

number of reclosures,

the sequential

automatic

reclosure

method

has

the

advantage

as

it needs

no

two-shot

ARC devices.

Moreover,

the

breakers

do

not

isolate

a

short

circuit

more

than

tn'ice

in

succession.

The

disadvantage of the sequential

automatic

reclosing

is that

when'the

next in

sequence

section

is

connected by the

ARC

-:-,-- ---t:- - ,,-a L- -l-'---------,-J

vlous segl,loll

IIlusI, f]e

orsoouueol,etl.

| - t- --11 - -

I

a IAUIL

O(iCtI.rS lll LIIIS

TiECLIOII

aL f,IllS

Simultaneousiy

v'ith

feeding

a closing

puise, the

nFtC

device

cioses

tire

circuii

t,rllrts lL .tD {;rcareu lrv Ltrc w-spee LJ.

pruuE('Ll(,Ir,

JO{*

CHAPTEiR ?.WELVE

OPERATION

OF

ARC AND

ATS

DEVICES 1\'ITII

RELAYING

365

12-4.

Substations

Without

Cireuit Breakers

on the

High-Tension

Side

The

costs

of

a

receiving

substation

may be reduced

by instailing

isolators

and

short-circuiters

on the high-tension

side

in

place

of

circuit breakers

(Fig.

t2-5).

Slhgn the

power

transformer

is

at fault its protection

trips

the

breaker

on

the }ow-tension

side

and

engages

the short-circuiter

on

the

high-

tension

side.

In

circuits

*'ith

heav5' earth-fault

currents,

a single-pole

short-circuiter

is

used.

A

two-pole

short-circuiter

is appiied

in circuits

with light

earth-fault

In order to

avoid

an increase

in the

operating

time of the protection

from

the side

of

substation,4.,

the protection

is-sometimes

allowed t6

operate in

the

case

of

faults

in

the power

transformer

before

the

short-circuitef

has closed.

In this

instance,

unsuocessfui

action

of the

ARC deviee

is

possible,

as the

auto-

matic

device

betweett

the short-circuiter

and the

isolator

will

not function

/10

kv

@

t

From

trons{ormer

prodectton

Fig.

12-5. Supply circuit of substation'rvithout

breakers

on the

high-tension

side

currents.

Closing the short-circuiters

causes a short circuit in

the high-tension

circuit

and

makes

the

urotection

from the suoplv substation

side

function

(this

protection

may

funttion

earlier, if its sensifio:it,y'

is

sufficient

to

operaLe

at a iault

in the

transformer).

The

breaker

from the side

of

substation.4 trips.

A compulsory

condition

is

the

tripping

of

the

breaker

from

the

side of

substa-

tion

,4 onl,v

after the

closing ol

the short-circuit.er u'ith tlre resuii

that the

protection

must be deceierated,

otherrvise

the

breaker may

connect

to a

persis-

ting short.

circuit

caused by failure

of

the isolator

to

function ciuring

the

no-

power

intervai

(see

below).

After closingtheshort-circuiter.

it

carries

a short-circuit current

(Fig.

t2-64).

Opening

the

breaher from the side

of

the

supply substation causesthe

cessation

.of

current flow

in the

circuit of

the short-circuiter

and irr

the primar-v of current

transformer

12. While the short-circuiter

carries

the short-circuit curucnt,

the

coil

of

electromagnet

3 functions and deenergizes after the short-circriit

current

is

stopped.

The compressed

spring

forces striker

13 to

knock out

latch4.

Isolator

6

trips

open. A similar

action

causes the relay 3TR

(Fig.

12-6b)

to

iunct.ion, this

ta}ies

p}ace

after the

biocking

contacrs

5BC-Z

have c}iecked

t,}re

cJosed position

of

the

short-circuiter

and

the

closed contact of

relal-

2CR

bas

checked the

current flow through the

short-circuiter, i.e..

the

opeu

position

of

the

breaker

from the supply substation side.

After

the

specified time,

whicii

is

Fig.

12-6.

Circui.t

dia3ram

of automatic

and

protection

units

for

substa[ions

having

no

breakers

on tbe

high-tension

side

(o)

a'c. rariant:

J

-

9upp.l-v

po"wef

.systern;

2

-

short-circuiter;

B

-

coil

of eiectromag-

n.9t;+-trippingdevice(latch)ofisolator;J-short-circuiierio_isoiator;T_capa_

c)tor;

E

-

auxi)iar!- reia)';

9

_

rectifier;

J,

_

voltage

transformer;

.:t

_

series

resistor;

Jz

-

current transformer;

13

-.eFrine:l

t4

-

resisior:

jJ

-

voltage

reguiator

(tube);

(b)

d.c. variant:

I

-

current-

transformer;

z-

-

cuirent

rela-l:;

'.r

-

time retay

and the

curent

flow

in the

short-circuiter

wili

start

after

the

oneration

of

the

ARC device

at

substation,4.

The breaker

wiil

be trinped..

Rbcoverv

of

the

supply to

the

intact.

transformer

of the

receivine

subsi"tion

can be

obtained

b,v using

a two-shot

ARC

device

at

substation

7.

Shorl

-

circuiter

is clased

remoteiy

6y

hand

(openino

bv

.-emo

va'6/

e' tSand

i

e {oca

i et oi

the

actuator)

from

yo{ta-qe

transformer

6600

/ fio

y

short.-e.i rr.rr i t.cr

qrh

i r..h rrl a \I

I!

a-r rrco nnprq I inn

(t)

(")

reduces

the

current fiow

in the

. Th.-

pwpose

of

time

relay

3 in the

circuit

on Fig. 12-6b is

to prevent

the

isolator

operating when

currents

may fiou.

to the

fiulred

place

not

onl5'

from tbe

supply

source

of

the

substation

z4

side,

but

from the

iynchronons

oi

asynchronous

load

connected

in paraliel

with

the

intact transiormer.

sure,

the ARC

device recloses

the

eker A

(Fir'.

4 2-5) snd reeslahlishes

tire

that

currents

from

the

synchronous

and

---t

--

asynchronous

coasting

motors,

sup-

OPERATION

OF

ARC

A}ID

ATS

DE\TICES

\\,I?H

REL.{-:-ING

367

@

12-7.

Use

oI

TFR'f

devices

at

substations

rvitl

out

circuit

breakers

on

the

high-tension

side

of

power

transformers

(explanarory

ai"grfit-

-- --

rn

[nts y

exam

The

section

AB

(Fi

12-8

is

fur

a!

5

of

the

sectiori

BD

(for'

instance,

selective

pr"i""tio"'z

protection

i-q installed

temporarill;1.

Fig.

is

disconnected

for

inspection

and

a

nonselective

CEAPTER T'WELVE

The nonselective

operation

can be correcLed b]'

several metiiods.

(1)

The ARC devices on breakers J

and 5 are

rendered inoperative.

The ARC

devices

on'all the other breakers of the

line,

breaker

2 included, remain llosed. When

a fault

occurs

section

BC,

this

section and breaker 2 are.

tripped in one

operation.

The

ARC

device

recloses

section

BC.

Breaker

I is closed

irr

time ,,. If

the

fault

persists.

the

breaker

in-

siantaireousiv trins.

-

Breaker 2

is closed

in

time t, onl5z"s11.1

the shor!

circuit has been

cleared.

The operation

of

the

protection

and auto-

matic

devices

is

srmiiar ii

sec[ion

BLr is

at

iault.

If

protection 3 is also rronseiective

u'i[h

respect

to

protection

units .Z

and

4.

Lhen to

correct the

protective operation

b1- the second

method,

the time

settings of

the ARC devices

serving breakers

2 and

3 must, be difierent.

tlrat of breaker

2, Ior

insl,ance.

greaLer

than

tire-

tirne sei,tiug

ci breaiier

,i.

tr"hen a

fauli

occurs in section

8C.

breakers

l, 2 anC

J are

t,riptred.

First the ARC device

closes breaker

J, then or

simultaneousl5'ri'ith

breaker

J breaker

.3 ii

-closed.

and

the third to

be closed

is

breaker

2. Af

ter

breaker

3

is closed.

iI

the short circuit

persists.

sections BC and DB

arc simul[aneously

tripped.

Tlrus,

breaker

2

is

closed onll'after

i,he short

circuit

is cleared. The

closing of breaker

2 ieestablishes

llie

suppil' to subst.ation ^8.

(3)

The

ARC

device intended

for-reclosing breaker

2 is

of the

trvo-shot

type, v'hile the

ARC deyices instaiied on brealiers

J and .i are-of

the one-shof

type. Ccrreclion

ol a

possible

norrseiective

trip is

obtained

due

to the

fact

tliat in

the case

of a

persisling short circuil

on

the line

BC or BD,

the

laulted

lines are

disconnected

after

a one-shot,

reciosure and

do

rrol

close

an-v more. Breaker

9.

tripped

nonselectivel

5,.

i. reclosed b1'the

two-shot

ARC device.

(41

When

breaker 2 is

auiomatically

reclosed..

the ARC

devicc

renrooes the accclera[ed

lonselective

protection

from operation

(it

had.

accelerated operation

until

the autontatic

reclosure).

The

ARC device of breaker

i

promot,es

the accelerated

protection

action after

automatic

reciosure. \4rlien a short circuit on

line

BC

persists,

the ARCdevic,e

recloses tliis

line sinulta-

neousll'

n'ith

the insertion

of the

nonseleciive

protection,

thus breaker

/

quickli'

trips- Tlie

second time, breaher J is

tripped

selectivel-v, as the

nonselective

protectioti

ott breaker

2

is

removed

by

t,he ARC

device.

(5r

Seouential

ARC

operations.

After tlre nonselective

tripping

of bre.akers I

and 2

in

the

case^of a short circuit on

line BC, Lhe

ARC

device

first

ci'5seibreaker

2 al a

smaller

tj rne

setting.

Some

time

Iat,er

after breaker 2

is closed,

the samc

ARC device

renders ilropcr-

ative t,lie

Eigh-speed

nonselective

protec.tion

instalied

on

linc AB

flom

tlrc

side

oJ'substa-

Lion A. The

ARC device

a

greater

time

after

the nonselec[ive_

protcc-

tion

of

breaker

2 is removed from

operation.

Thui, the

persisting short circuit

on

line.BC

is

repeatedl5'

selectively

tr1iOO*U.

tive

for

inspection.

It

is

clear,

that

the

tion

and

seiection

of

an

ARC

a""iw

ocal

conditignl,

possible

time

settings

ove

the

ARC

devices

from

operation

i's

cirucit

configuration.

12-6.

Sim4if.nog

Primary

Connection

Cireuits

and

Proteetive

Relaying

In

the

opetr

ring

circuit

with

simplified

protectiou

relaying

the

ARC

devices

allow

the

load

to

ie

t"pfrita

T*t

-t*o

gr.,i".,

tie

seti-srarring

of

which

rakes

place

after

an

ARc

device

opttrtioo

u,ith

no

-disturbance

to'

the

production

process.

OPERATION

OF.ARC

AND

ATS

DSVICES

'W'ITE

RELAYING

into

"tl""iie.ii,1,"1"rf

,ll,f;ii

y"li:

rlqtiiT-from,starioo.M

g.

y'/

and

ma-v

be

also

oonnecred

a

,{,&

calls

for

installation

of

com

:_--J

rY-vwu, _

uue

uDudr

Pl-u

L

rcar,ed

relaying

eguipment,

?AO

Fig.

12-8.

Ring

systern

I

possl

rzrng

pro IOn an

The

2

is

provided

with

an

ARC

device

eld

.norfoaily

good

practice

back-up

protection

units

and

not

to

riupiicate

invoived

irigh-speed

protection

24-2076

rotec

a

"low-rating"

or

is

j

(to

reduce

losses.

it

is

'?r_!

i_

rr -

---.{rit,F.!€€sgri::.-3jk

370

CEAPTEA.

TWELVE

OPERATION

OF

ARC

AND

ATS

DE\iICES

WITIi

R.ELAYING

371

closed).

In-such

cases

as

thes6,

the Iines

It{A and.dr\; ma1'be regarded

as lines

supplied

at

one end.

4.

Lines

M-i-2-3-4-Ir

are iong lines

c,onnecting

pov'er

s],stems

M

and

,[

(Fig.

I2-ge).

Substation

3 is

the

\oundary

betrieen

the pou'er

sj'siems.

if tbe

polver

svstems

.ir'

and

,A'

are

paralieled

through

a

tie iink,

the line

prolection

must tal<e

into account

iossible

asynchro-

tl

1

tTrTl

I

IEIt

4*'

Fig. 12-9.

Variants of

power

supply

to circuit

sections

(o)

substation

connection

to

parallel

lines;

(b)

same

by

T-circuit;

(c)

same by H-circuit;

(d)

ring

circuit;

(e)

installing

ATS device

on

single

intersystem

lines

nous operat.icrn.

If required

protection

units

are not used.

breaker

J' is hept open

and

is

closed

by the ARC

device only

q'hen

the

power

suppll'fails

from

the side of substation

/ly'

or,Ai

(for

inst,ance,

when

tbe voltage across line

2-3 or

across

ti:e busbars

of substation

J

disappears).

The entire circuit

i/.[

will

be

switched over to a

one-side

supply

from

tbe

power

systern

M,

v,hen the

busbar

voltage

of substation 3 fails, and

to the supply lrom

tbe

power

system

y'y',

when the voltage

across

line

2-3* disappears.

the

undervoltage relav

must

be

greatbr

than

tbe

total

time foi

tripping tbe

line

frori-the

sidi

are

connected

to

tbe

t-,:

I:r^r-tltough

brea,kers

or

high_rension

fuses.

installed

at the

L.

SI

(")

Fig.

t2-10.

Circuits

of

,,deep"

service

entrauee

(o),fuees

.or.breakere

are

installed

on tbe

rugn-lenston

6lde

of

the

translormers

of

receiving

eubsts

tions

f

a) isolatoil

A;d

;i";:

circuiters

.

laiiure

oa

the

conesponding

to

them

and

the

fresuencv

rrvv,

wurv!

Lrrp

ur_efl!{ers

I

oI

J

Ln

sections

oJ

tbe-

receiving

subsGiions-or

orops,

and

reciose

breaker

2.

e

case

vr

o

yur|,aEu

power

flows

+

Srr^h ^na-^*l-.- ^^-i:.:^*^ -^-- L^ -Il^---^J :I +L^ ,.^l+-^^ +ha +^nrnih6lc ^{ +h.

uuuu

vPEralrtrB uurJur!tul.l-\

trtaJ

lrts uttu$,Eu

tl

LlrE vurLdxE dvrvDD

errc

uElrrlruqro

r,1

lrrL

ioads of

one-eird subitations

is'not

belou'the

permissible

}evei, this is

possible,

but

rarell'.

Wlren

nO

24+

Illustrated

in Fig.

72-70b is a "deep"

service entrance circuit

with tbe

use of

isolators

and

short-circuiters

at the

H.T. sides 6l the

step-dov'n substation

transformers.

Selective

disconnection

of a

faulted transformer

is

promoled

b-v the combined

operation of the

short-

circuiter,

isolator,

Iine

protection,

transiormer

prot-ection

and ]ine ARC

device.

. .Tht

supply to the

loads

connected to

the

L.t. busbars of tbe

transiormers

is

promoted

by

the

operation

of the

ATS device ciosing

the section

breaker. The operation of-the ATS

device should be

as

rapid

as

practicable,

regard-

Iess

of the

operation of the

ARC devices

installed

on tbe

H.T.-suppll' lines.

The

use

of

such

a circuit

does not ensure ieli-

able

service

if a svnchronous load

is

cbnnected

to

ihe busbars

of

ihe consumers'

substations anti

if

aL- -- - ------l-- I --l -- --l , .1

rtre

cotrsulllers eurProv

rocar

power pran[s

oI IoE' oI

considerable output ratins

(examples

are

power

piants

utilizing

liod

rction-wastes).'

If

that

is the

case,

ri'hel

the supply line

is

trinped

due

to a short

circui!.

the

short-circuit

curr'ents u'ill continue to

iit,u'

to tbe

point

of sliort

circuit

from tire synchronous

load

or tbe

generators

cf

the locai

power plants.

The

result

will

be eitber

an

unsuccessiul.

at:'uamatic reclcsr:re

due

to a

pe,isist-

ing

strort-circriit

arc oilas*ynchronous closure

of

the

syncnronous

II]acnlnes.

IJ a short circuit

occurs

within the

zone

bet-

l'een

the

breaker of

the

step-down

transf

ormer

and

the

isolator,

the

currents

fiom

tbe

synehronous

machines oi

the neighbouring

substations

rvili also

flou'

to the

point

of faulr. Irr

this

case.

tbe

isolator

ma1'

either iatl

to

open. the resuit being

an

unsu-

cceisfui ARC from

ihe

suppil'

substations.

or, if

the

short-circuit

current

is, alter

tripping the suppll'

Iine, insufficient

to bold the isolator closed, it

oDens

and interruots the current

generated

bv

the

synchronous

machi'nes of the

neighf,-ouring

subitati-

ons

and

thus

damases

the

isoiator.

JIL CEAPTER'

T'WELVE

(6)

systerq

is ilterrupted

[12-5].

s'ays

6.

advisable.

A

substation

is furnished with

:* -^-^ll^t rL^ ^L^-e ^:-^--:4

lu

Pdr

iarrlir,

lurt tltul tr'-(;ll'-trul t,

(")

Fig.

L2-11. Supply

circuits

of receiv-

'

ing

substations

(a)

parallel

operation

of transformers;

(b)

Bectionalized

power

supply

to

busbars

The

operation of tbe

ATS

devices

instalied

at the L.T. side

of

tbe

power

transformers

al-"o

beconies more complicated

due

to the

effect of

tbe

s-vnchrorrous

maclin"s

(motors)

cor-

nected

to the

busbars

oi tbe standby

supply

sections. As

already

mentioned,

the

ATS opera-

tion

should

be

coordinated

s'ith the

diiconrrection

of

the s-\iiiclrrorious ]oad or iis iranster

io

operation

wi(houtexcitationf12-a].

The

circuits of

the

ARC device

servicing

the

H.T.

lines

aiid the circuits

of the ATS

devices

installed

in

the

L.T.

sections shouid

-be

tulfilled

with

"waiting"

for

the

voltage

across

ihe eonnections deenergized

at the

power

system

side

to

drop to-40-45

r,er cent

oi

the

nominal

value. The

cenerat6rs

<if lc,cal thermal siations

should

he

|rovidea

wittr high-speed

sectionalizirrg

proteciion

units

isolating these

generetors

v'ith

their

load

share

from tde

busbar

sections-oi

tbe substation

u'bose

iuppll.fiom

the

po$'er

ulJsr

q

!s.

two translormers

(Fig.

72-11\.

When these transformers

:^ ^..^L

+L-r

-^^^+^-^ .*-.^+ L^:--+-ll^l 4^

^-.^rti^

PUWEI

l)

DUU!

l,lrdt

lEdUlViD

IUUDI

!E llDKllgu

LU EuDus

de'ice

in

the

transformer

functions

aDd

op*ruUoo;i

il;;i[1#il'#';";ii

bited.

The

less

important

loads

of the srrirsta{i^. o.o rrt ic^^--^-*ar +^ b-^--^-4

oPERATION

OI

Anc

AND

ATS

DEVTCES

.WITE

RELAYING

o/o

the

operation

of the

breakers,

or

more.

expensive-

breakers

of

higher po\r,er

rating

must

be

installed'

14'hen

the

transfor-Lti-"pl.*te

separateiy,

!h-e

short-cireuit

currents

deerease

and

there

is

no

need

to.

instail

r"""i.i"i

o.

*6ru

po#.rtur

breakers.

Separate

oneration

of

the

transforme".

'"nd

theii

use

as

stand-by

units

for

each

other

Trith

$tisfactoiv

service-t"

it"

lolas

is

obiained-i-o'i*t"tting

ATlq

de*ices

on breakers

j-J.

rr

breaker'r

or

J

is tripped.-i[=.

erlr;;i*;i"ffH;;-k?r"i.-

sL"u'

(qt

ft)

Fig.

L2-72.

Station-sen'ice

suppll,

cjrcuits

irJ

-

stand-bf,

tra'Isformer;

T2-T4

_

working

transformers

7'

Shou'n

in

Fig'

72-72

arc

the

main

power

station

connectjon

circuits

in

rn'hich

section-

alized

supDh'

of the"station*serviie

b";b;.;ii

"..J1e

lt"'iab.1'

t"urrrformer

ma5,

he

connecte6

ejLlier

to't'bi

H.T.

trushai.

o. t""trr!-generator

uoii"gl.--ia']ren

the

v",orliing

transforrner

is

disconnect'ed.

the.4TS

device

cuts

in ti.

ii*rany"t""l"ror"rrt;"d

tr;;;i"i"tt

"

deenergized

sectjons

to

its

suppl5..

12-7.

step-Dor*'n

Transrormers

at

Remote-controiled

Substations

..

If a

substation

Jras

two

transformer-"

u'orking

into

different

sections,

the

ATS device

is

allou'ed

t.o

close

a sectjon

breaker

a?ter

trippins

one

of tlie

trans_

formers

onilz

wfusn

this

tripping

causes

no

into]erlbi;';-drjJo"J

r,o

rire

orher

transformer

in

operation

The

circuit

shouid

be

so

designed.

tlrat-tripping

a

transformer

by

the

over-

cuffent

protection

causes

the

operation

of ttre'enC

device

"na

prohibits

the

operation

of the

ATS

device.

With

the

internal-fault

protection

units,

the

ATS

otl

CEAPTER

TWELVE

OPERATION

OF

ARC

AND

ATS

DSVICES

'WITII

RELAYING

device

either

automatically

or

remoteil'

and reclose it with the

aid of

an ARC

device ajter

automatic

disconnection

of

tbe transformer.

If

the

u,'orking

transformer

is

overloaded and there is

a

standby transformer

which

can

be

connected

in parailel

to the

one

in

operation,

the

connection is

better

performed

automatically.

After

the

overload disappears the

standb-r'

transformer

is then

automaticaliv

disconnected.

The.

standbv

transforrner

*rv

b*

c.onnected. and disconnec.te.d bv an auto-

J-

rnetir. nncref.nr i{ f.ho npaL'lnodc

qro

foLon infn oacnrrnf in'tho T..,o.l Q.},ar{rr'lo

vrJe pvqrr

luUv

qvvvuuu

ru LIrv

Uvqu vvrrvuutL

of

the Jubstation.

fhe

connection

of the transformers

ma-v be also

governed

by

the

overail load

of

the

substation.

If. for instance, the ioad

of

the substation

rises

to

110

per

cent

of

the

nominal

vaiue

of one

transformer, the

other

trans-

former

is

automaticallS'switched

on. If

the

overall

consumed

porver

decreases

below

90 per

cent

of

the

nominal value

of oue

transformer, the

oiher

transfor-

mer

is automatical]v

disconnec't,ed.

'..--

12-8. Automatic

Discriminating

Redundancy

Automatic discrirninating

redundancl,[r1-z]

is

used for

automation of city'

power

circuits, whose loads

can accept

relatively

long (several

seconds)

inter-

rupt.ions

to

the

service.

The

loads

of a cit,y

po\ver

circuit

are

supplied

over

radial

lines

through

transformer stations.

For

m.utual redundancl'

purposes

several

trunk

lines

are used.

A

trunk lirre power

suppl-v

circuit

is sirown

in

Fig. L2-73.

Tire

transformer

stations

b

to e

are supplied at

one end

from the

busbars

of

substation

a. Each

of

the transformer

stations

ma]'be

switched

over

t,o

another

trunk

line

suppiy

through

the

transverse iinks.

Under

normal

condi-

tions these

iinks

are isolated

at substations

b

to e.

Piiot breaker 7

is furnished

s'ith

a

protection

unit

which

responds with

the required

sensitivity

to short,

circuits

occuring

on

any of

the -sections

ab,

bc, cd, and

de. The

operaiing time

of

this

proteciion

is

0.5 s

(discriminated

against

the

operating time

of

the fuses

at the

consurners'entrances).

Breakers 2

to

8 are

load

switches not designed

to

interrupt,

short-circuit

currents.

An automatic

discriminating

redundancy

(ADR)

device

opens

these

Ioad switches,after

breaker / is

tipped

and the trunk

line a,e

-

deenergized.

to suit the

diagram

(Fig.

12-\3b).

The tripping time

of

even

numbers

the

tripping

time

of

the

odd

number

breakers

is

(tt:te)(fs(ts

The

ADR

device

operates

as follows.

When

a short

circuit

occurs

on the

line,

sa5,

at

the

substation

a is tripped,

currents

showi'in

Stand-

6y

from

?nd

drun.I

ltne

point

8C, before

breaker

I

Fig.

12-13c

by

solid

arrows

'CR

tAP

tircuil

to

trtp

sviicbes

->

VLE0

F/

eyen

./{os

77

Circaii.{o

Lrzp

srrLtches

y,iLh

odd

//os

+&rmi./

ia

conneci

slond-

by eatronce

open

the

at

point,

Fig'

12-13.

Aulomatic

discrirninating

redundancy.

Norma]ly

open

sg,itclr

is

(a)

circuir

o:lq3pj,,

rg2-.-9gg1g^ti1;tiJ:

T

if$r

proteciion

devices;

(c)

expranatorl.

diagrarn; (d)

scheriatic

aiaglam

oi

;-Dri";#ice

(ro,

substatjon

c)

The

rela5,

lAR

operates

and

tripping

breakers

with

the

even

breaks

the

conta

c.L lAR-S

in order

to

numbers.

\\zhen

a short,

circuit,

occurs

.SCr,

disconnected

in

this

wa

are

the

trippins

circui

/ls Lre

snort-crrcurt

current

flowed

in

section

5-6

the

reiay

lAR

on

the

ADR

device

of su,itcir

6 did not

onlS'

to

tiie

polnt

.9Ci,

function.

Thus,

su'iteh

d

(Fie.

t2-13b).

Switch

J

1.2

,1 ?

2.2

t.2

q

/. D^ Rf ai tn-)-

iffiii',;"'iiii!f

VR-|

z

4CR

zAR

cr

tzlta

(

fo

(

Ir and

irips

in the

time

cietermined

by

the

characteristic

I^

CEAPTER

TWELVE

OPERATION

OF

ARC

AND

ATS

DE-\IICES

WITE

RELATING

.i6

:lg

3'

A-fter

distance

connection

the

accelerated

protection

time

should

be

e

raised

currents

resuiting

from

starting

place.

makes

it

possible

to

achieve

radial

supply

ply.

The

sectionalization

of the

srrbstatioo

rr€nts,

thus

facilitating

operation

of

the

L

construction

costs.

ices

must

be

coordinated

with

the

appro_

vices

of the

actuators

of

the

asl,nchronous

tic

devices

helping

res_vnchronization

of

.,

slfichronous

motors.

=

6'

The

combined

urq

of

isolators

and

ARC

devices

in place

of

circuit

brea-

kers

should

take

into

.

ccount

the

t-vpe

of

toaas

""a,-i"'p^r{,icular,

the

fact

that

after

deenergizing,

tlie

ioads

continue

to

maintain

for

some

time

the

ter-

-

minal voltaoe- This i" oenoniollr' +-,,^ ^r ^ ^--^r--- r t

_ _ __D_

^v

vsyvvtqrrf

!r uE

rrl

a

Dyucruoltous

loao,

is

tripped

b-v

its

ADR device

in time

ts.

This

is done

by

the time

rela_v

?fi

(by

the

contact

TR-z

whose

circuit is not

eontrolled bv

tbe contacts

of relav

1An.

Tbe

breaker

of

the

reserve

service entrauce

is

closed bv

the

ADR

device

when

one of

tbe

service

entrances

of

the

main suppl5'trunk

line is disconnected

(even

or odd, Fig.

12-13d;

and the service

entrance

of

the reserve suppiy

(cont-

rohed by the

auxiiiary

contact

BC of

the

reserve service entrance

breaker)

and the contacts

2AR-2

or

LAR-Z

are closed

The

contaet lAR-2

of. tbe

ADR

devices

of

the

breakers

in the

circuit car-

'

ryrng

'rhd

short-circuit

current closes.

Ciosed

is the

contact

2AR-2

in

the

ADR

devices instailed

in

the

main supply

trunk

line

sections

s'hich

carry no short-

circuit

current

(the

relay 2AR

functions and

breaks

the

contact 2AR-2. if the

eontacts

of

voltage

relay

VR-? and

current, rela;'

4CR

are

ciosed). A-fter

the

current

flow

stops,

the

relay 2AR holds

itself

closed

with

the

contact

zAR-l

until

the

voltage

is

reestablished.

Thus,

the

ADR device

discriminatingly

trips

the faulted section

s'ith

the

aid

of

the ioad

ss'itches

(u'hich

are. not, intended

for interrupting

short-c.ircuit

currents)

subseguently

changing the

load to the suppll'from the

reserve

trunk

line.

\\7hen

a short-circuit,

occurs

on

the busbars

of

tlre

tran-sformer

-substaticln

(for

instance, at

point

SCr),

the short-circuit

c,urrent

fiow, untii

the

instant

breaker

f trips.

is deterrained

b;' the broken

arrows

(Fig.

t2-13c).

This

differs

from

tbe

case of a short

circuit

at

ocrilt, S'C,-{considered above)

in

tiiat. no *qhort-

circuit

currenf flou's

in section

5-6. Therefore. the

relal' 5CR in the

ADR

device

of

switch 5 does not

function.

the

relaS /,4.,R

does not operate

and

the

contact

IAR-7

remains

open.

Since,

v'ith

a short

circuit at

point.SCr,

the rcLay 4CR

functioned,

the

contact

2AR-2

would

be opened in time

t5

at the moment sv'itch

5

opens. The load

switch

of

the reserve

service entrance

of

the

substation

c

wiII

not be able

to

close.

The

fauited

busbars

will

be

-tripped

open

b1.

switch

3

in

time lr.

The deenergized

substations

b,

d

and

e

would

be automaticaliy

trans-

fened

to a

reserve

trunk

line

suppll'.

The

automatic

discriminating

redundancy

method causes

long interruptions

to

the service,

a

fact

which

is

the

main disadvantage

of

this method of

trip-

ping

and reserving

the sections v'hen

they

are man-v

in

number.

12-9.

Conclusions

_

{.

In manrr

instances, the

combined

operation of

the

protective

relaf

ing,

ARC

and

ATS makes

it

possible

to clear

short

circuits ulore

quicklv, widen

the

fieid of application

of

''the

ARC and

ATS

devices

and high-speed

simpie

type protection

units.

2.

It

is advisable

to use

protection

acceleration when

high-s d

protection

for

protection

acceleration

before and after the aut.omatic reclosure.

-^^l^^,,-^^ ^-^ -^^-:.I.l^ +^^

I

EUIrJDLT.T

gC

O,I

E

I,I,DDIJJIE

IJ('IJ.

possibilities

of

simpiifS'ing

protective

relaying

cievices

r-hen

ATS

the

supply

is

the

ode-end

i"di"l

ijp"

*.

compared

to

the

ring

power

i2-i0.

Review

Questions

1.

Enumerate

the

devices

are

applied

and

supplv

svstem-

faulted

section

be enzured

b5,

comb-

of nonselectiv;:

protective

rilal,ing?

6. \4rhat

are

ttre

phenomena

which,

v,ben

taken

into

account,

limii

the

po..iliti'ti"s

ol

acce_

lerating

the

proreci.ion

operaiifi;ffi;L"

function_

ing

of

an

ATS

device

inst'Ctt.rl

""

rr,"

*"ir^-

hF^.1-^-

ing

of

an

ATS

device

inst'attea

on

*u

-."iioo

breaiier

of

a

substation

in tbe pre*sence

of

asyncirronous

and

synchronous

loads?

provide

Flr*ho. cim-la

carrran*i^l arr*a*a*ia

er4lrrv

DvYuesllql

ouuurltqllv

tc

teatures

of

ATS

devices

used

at

remote-controlled

substations?

r

Chapter

Tlzirteen,

AUTO}{ATIC

CONTROL ELIMINATING OVENYOLTAGES

ACROSS

EQUIPMENT

13-1.

General

The

growth

in

power

station

outputs, Iong distance power

transmission

and

integration

of

power

svstens into one

srrper

grid

for

the

whole

of the

Soviet

Union

means

the

construction

of

500. 750

kV,

and

more,

transmission

lines.

The

one-end

disconnection

of

iong

lines operating

at such

voltases

causes

overvoltages

both at the disconuected

end and

(to

a

less

extent)

at

the

end

'

connected to the

suppiy

substation busbars.

The termiuai

voltage

of the

equip-

ment

ma]' exceed

the

permissible

value

for

its insulation.

To illustrate

the

operating

principles

underlyiug

automatic

controis

which

eliminate

dangerous

overvoltages,

we

must first find

rvirat

causes

these

over-

voltages.

The electric power transmission

lines

with

distributed

inductive

reactances

aud capacit;i'susceptanc,es[13-iJ

ma1'be

presented

b-l,T

or

inverted

U

equirtalent

circuits

(Fig.

13-1).

the

legs of

which

include the

lun.ped reactances.

Tbe

relationships

given

below

are

correct

for

lines up

to

500 km

in

}ength.

For

longer

lines, the voltage

calculations should

be

based

on

the expressions

used

for

circuits

with

distributed

parameters.

The

lumped

reactance

value-*

aie

determined

u'ith the

heip

of

the

specific

inductive

rs

and capacity r,s reacLances

for each kiiomet,er

of

line

length,

the

re_sist,ance

being neglected.

Lel

U

urs

denote

the line "beginning"

voltage

and

U"n.a

the

open

"end"

voltage. The

difference

between

these

voltages

il AU.

From

the

diagram

in Fig. l3-1,a

it is seen

that

LU': I'czrl12

From

the diagram

in

FiS.

13-tb

AUTOMATIC

CONTNOL

ELIMINATING

OVERVOLTAGES

Thus

hence

Ub"E:U"na-LU

fJb"s:U.^d

({

-0.05

#

*)

(13-6)

t!12'7\

\rd-r,l

(13-8)

for

the values

0.297

Ohm/km:

":#-i_a.s:Ltz

.Figure

t}-Lc-shon's

the ratio

[.t"n6/[.)6"n

as

a function

of

I

?glr"

coJr_elpgl{itq.

to

500

k\;,

50

IIz tranJmission

lines

(st

:

ilr"

:

3"71.10-6

S/km;

and

zg

:

0.27

.106

Ohm.kn).

*l

f

-:_

-2

ra

^t

I

t-i

r-

:J.

-r

-i-

:

1*^

't

-t

i-z. I

J-Z

i,'

'

,i"

-+

(t)

T

I

(aj

(13-t)

(.r3-2)

(13-3)

(r&'4)

(13-5)

0 200 40A

600

500 *m

tL/

Fig.

13,1.

Voltage

across

open

end

of long

power

transmission

line (open

breaker

is

showr.r

in

black)

(o,

b) T and

inverted

U

egulvalent

circuits;

(c)

volt-

age of 500-k\7

line

-beginning"

and open

sendl

versus

line length

The

currents

I"c

and

fE

are

.bt

I

6Iy-L

From

Fig. {3-1c

it is

easy

to determine

end

of

the transmission

line with

respect

suhstation (beginning

of line).

If

the

busbars

to which

the "beginning"

the

value

of the

voltage

at

the

open

to the

busbar voltage

of

the

supply

of

the transmission

Iine is

connected

are

not

the

busbars

of

an infinite-power

svs

substation

also

rises when

the

receiving end

lent

circuit

in

this

c.ase has

the

form s-hown

of

the

line

i-q tripped.

The

in Fig. L3-2a.

The

vector

the

equrva-

diagram

A{J

:0.,

*

IzU

"nd

is

shown

in

Fig.

13-2b.

CHAPTER

TEIIRIEEN

AUTOIUATIC

CONTROL

ELIMINATING

OVERVOLTAGES

381

The busbar

voltage

of the

supply

substation

is

Li

b"e

:

E

pn

-T

I

cLsust

li,

-tr

,

Uend't^

-'

oeE

-

"pn1-

4

LLaVst

,

Eph

,

Ueoc,

tsgst

l:F---F-::-L_-

Ub"E,

UbeE

zC

:L-

!

-pil

"u't

i.e.

Duee

'

Y"

zc

(t

y,"s)

E

pn

"

\Alhen tripping

the

open

}ong

lines

carrying

the generation.

the

of an

increase

in

emf

of

the

generator-"

(E;")

inoulti'

be

considered.

>ar

rvhen

a

long

transmission

line

is

connected

ne

is

disconnecled

at

one

end

the

reiationships

(+)

(ccl-"r*

xar/2):

(*)

+

(rlrb)

For

the

example

under

consideration

at

normal

freguency

the }ine

capacity

reactance

,.

0.27.106

ts/l:-=;--:540

Ohms

ot,

q-I

19

*O

tO? <nn

r4

-E ^l --

v.-!

t,

twltr

:

rJ

L,,IJIIIS

ui,,.

on

(kY)

.5052

""

:-Jl111a]-

zdc:

m.0.23

:

235

Ohms

transformer

iaduciive

ierclanre

,--u?-^.pn

$Y)

-

5052

"r:

-S-(MTE-

r".

:

-]t-.Cr.t2:121

Ohm_.

To

the

condition

of (13-i5)

corresponds

the

relationship

/ {t \2

Hence

\i )

Q3s+

121

+

75):

546

I / Etr,

ir:

l/

ffi:l,'T.ts:1.12

Thus'

for

this

exampje,

the

appearance

of selJ-excitation

is clearly

seen

u-]ren

the

gener-

ip-"":9-:*:r^fe-s

b1'f2

prri*i:b-o;ii,.

nomin"l

value,

i.e..

at the

freouencv of 5F, r{2.

",o'

io"".il":il::,fr.::

b;"il*:

,i",lif l* I,T

;d;iffrl,"Ti,l::

i".:,:1.;t,'?:&l;,"."'r,j,.#r:ff;.

Researchesshou.,

iio*eiie.r-ra+r;fi;;rff.,;jffi,i"i"lijli;

l,i;',t

u'"|i.ll?Hi.,lii:.%i,:ff;

ars

even

before

the

comptete

resonance

corrdition.

/49 n\

\

I'

J- i7i

(r3-10)

t42

'l,t\

\

rL'-r

r/

t42

,tcr\

\rd-1:/

( 1O- 1

l/

possibilit-v*

This

mav

linp inrlrra+irr6 raaa+^-^^

IYE

rEOW!dUCE

geDerator

inductive

reactance

k)

Fig-

13-2.

Caiculation

diagram (a)

and

vector

diagram

e n

d tri

p

i n

g

of

i

o n

g

p

orver- tra

l,s"*i

r,.i

"i

"fi::

rll"ii

sii n

ce

occur:

Jirst,

due

to

the

machine

acceieration

when

the

joad

is

discarded

(up

to

130%

for-hydroelectric

generators)

and,

second.

due

to the-

generator

self-

excitation

effect.

An increase

in

_the

generator

speed

raises

the

emf

of the

exciter

carried b1'

the

rotor

shaft

and

the

result

is

an increase

in

the voltage

".to*

the terminals

of

the

stator

u'inding.

,

Tire

self-excitation

ma1'

be..explained

in a

simple

s.a],

as

follov,s.

--, lnl:t_^?^igg_

transraission

Iine

is

tripped

"t-tlJ

t*""iving

end

and it

has

a

generaror

and

a

translormer

operating

as

a

unit

at

th-e

-suppi5,

end,

tbe eluivalent

circuit

*"i

lo

pr._

sented

h_v

the

-circriit

diagram

in

Fig.

IB-2a.^'

'

If

the

totai

inductive

reactance

o-f

the

circuit

becomes

equal

to

tl-.e

bapacitl

reactance

of tbe

line.

i.e..

if

(6)

(b)

for

of line

tbe

ease

of one-

and pou'er

st'-

appears

even

before

the

compr"te

lei-onail.'""i,aiiilii,l

(26

|

x7*

zfl/2):

a"11

t 4 2 4 /,\

trv-rr/

*,-q:"qili9,"^^oj^t.j9l"lce

arises

with

a

resultant

bear,]'current

flow

in

rhe

sraror

u'inding.

lines

with

one-errd

operation

the volta-

g

of

a

tie

line

or when

it

is

tripped

at

lrtialll'

compensate

for the

effeci'of

the

ection

of

reactors

at

both

ends

of the

,

costs,

reactors

are generally

connected

stations.

The

reactors

may

be

connected

r?o

ponrrimrl

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

^. ^ Ili:

"_I3l"i9_""nnot

be

eliminated

by reducing

the

e:icitation

manually

or b1'

means

*-lji:li_l'-.ry1.119t;

for the

current

flov'in.the

statii

circuit

is

maintainea

tir,rh;;-:;;;;;i

uragrrtsLruru

lrl Lrre

rrame

ano

pole pleces

ol the

nacbine.

j:fl:"._:t1+e

daTage

to.

t

-he

power

irandti"j

-equipmenr

of

\ rrlLI'UI

Ul

ltr9

OD/OII

SUtit.r.hino nnprof innc ^h +],o nnna{ ara

devicgs,

-------.'

wrvse

va uAe

rvauuurD

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

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