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

l?2

GEAHNER FOIIR

In

recent

years,

besid.es isolating

generators,

rapid

(within

fractions

of

a secondf

untroading

of s-eam

turbines is

rnost

wifi

Thffi

effective

braking of

the

power

units

without

their

disconnection

from the

cir-

cuit.

The

entire

unloading

process with

subsequent

recovery

of turbine

output

takes3to5seconds.

The

effectiveness of

various

methods improving

the transient

stability

wili be

now

illustrated by

an

exampie

of

a

short-circuit

fault.

The

instant a short-circuit ocsurs

the electric

power

of

the

generator

changes

from

curve

-Z to

curve

2

(Fig.

4-17). The

turbine

output remains the same

as it

Fig.

4-17. Characteristic

of

po\r'er

transmis-

-sion

process

in

emergency

conditions

r

-

electrie Docier

before fault:

?

-

electric

Dower

tiurins

ihort'circuit:

3

-

output

power

developed

b)

tuibines;

4_-

electric

power

after fault;

Sabcd-

accelerating

areai

Sble-

detelerating

area; ad

-

lncrement

in

angle

6

for

tbe

short-circuit

period

Cr=4 90'

Fig.

4-18.

Characteristic

of

povier

transmis'

sion

process

with

electric

deceleration

cf

gene-

rator

J

*

electricpower

beforefault;

2

*

electric

porver

during

sbort circuit:

3

-

output

power

deve.loped

by

twbines;

4

-

eiectricpoweiafteiJault;

Soebcd-

accelerating areai

.sr_yph!-

decelerating

area;

ab

-

insr€ment

in angle

6-prior

to

engaging

decelerat-

ing device and

clearing sbort circuit

t'as before

the

fault

(straight

line 3).

During

t.he fault.

while

the

short circuit

is

not

cleared,

the

angle

6

changes

its

value

from 6,,

:

6r

to 6, due to an increase

in

generator

speed.

After isolating

the

short

circuit,

the power

rises

and

its

value

is determined

from

curve

4.

The

excessive

torque

accelerating the

generator

is

indicated by the area

$auca.

Stabiiity

will

be maintained

if

this

accelerating

area does not exoeed tbe

decelerating

area

,56"1

(in

this

case

the

generator

output is

greater

than the

output

power of

the

turtrine and

the

generating

unit deceleratcs). In order

to ensure the

iransient

stability

of

the

generator

the

aceelerating area

on one

haud, rnay be

reduced

during

the

fault

and,

on

the otber hand, the decelerating &.rea

may

be increased

after

clearing

the

fault.

6n= d,

90"

It

is

seen

from

Fig.

4-77 that

this

aim can be attained both by

the

automatic

excitation

control

deviecs,

which increase the ordinates of curve 4 and, thus,

AUTOMATiC CONTROLS FON MAINTAINING

STASILITY

the deceierating

area, and

b-v

the devices for

rapidl-v

isolating short

circuits,

which decrease

the

acceierating

area. The

emergency

biaking

of the generators

by cutting

in

a

resist'ance

for

a

short period

increases the decelpratiug

area due

to

au increase in

the

electric

}oad w-ithout

changing the

turbine

output.

For

+"hi.s

case.

the torque

charaotelistios are

those

sho*r in Fig.

4-t8.

The method

for

securing

the transient

sta-

bility by disconneoting

some of

the

generators

is illustrated

in Fig.

4-19.

After

the

generators

have

been

disconnected, the

decelerating

torque

is indicated by

the

area St"/e which

is

far

Iarger

than the area ,561"

shown

in Fig. 4-17.

When making

calculations

it

must

be

kept

in mind that

disconnecting

scme

of

the

gene-

rators

ingreases

reactance

rt2

somewhat with

a

resultant decrease

in

the

ordinates of

the

power

characteristic aiter correction

of the

fault.

RapidlS'

unloading

the

steam turbines

as

a mearl*q

of ensuring the transient

stabilit_v

of

the

generators

became feasibie

after design

of

!!e.

-qiqg-i.io-q,ydrquiic

converters

(EHC)

rrhich

nacie it

possible

for forced

pulsesfrom

external

electrical

'devices

to

be

f

ed

to

the

hydrauiic

speed

governors

of

the turbines.

The

usual

speed

governor

design

employed

under

normal

operating conditions is

not

sui-

tabie

f or

rapid changes

in

turhine

output

rilrr.i-o o froncionl nrnaacc lro^or."^ ^{ ifo o1.,.',

e

qr

rrrA

u

el

uu€rvU I

Vl

VVEJJ VgUq UrrE

VI

l9!-

JIU

W

^^+.:^--

rnl.^-^f^-^

^ir o^--:^a -^^J- !---L:-- - r

a(,Lrull

.

r .Lrcl-tilUI-u, art

DU

vrer.-rilauc

turulller\

oI

capacities

300

I\{W

and more

are now

furnis}red

,r

OQ

o"

6n-6,

go"

/60"

Fig,

4-19. Ciraracteristic of

pov/er

transmission

process

rvhen

some

ge-

nerators

of

power

transmission

sta-

tion

are

disconnect,ed

i

-

eleclrie

poR'err

before

fauli; 2

-

electric

power

during

sbo!'t eircuit:

a

-

output

power

of turbines

before

disco-

nnection

oi some

of

generators',

a'

-

same,

but

r.hen

some

of

generators

are

disconnected;

1

-

electric

power

after

fault

witbout disconnecting

some ot

se-

nerators;

{'- sarne.

but after disconnbc-

tion of

some

oi

generators:

S^r.^^*

acce)erating

area;

.qeibs-

ciecele"l"iiing

area: AA

-

inr:rement- ifi angie A nrinr

to

ciea rins si,

r,i{

-c,

rc,

ii-

an d-

iil

s etrinic-

tlng

some

ot

generators

with

EHC devices.

The

EHC devices for

200

]\,t\\i turbine.s are

available

at

option. The use

of EHC t'ith

electrical

inputs

allou's

its

use not,

onil'for

sta-

bility,

but also for

.a

series

of

other

problems (prevention

of

turbine

racing,

Iimitation

of

turbine

output v'hen the

steam

pressure

is insufficient,

etc.).

The

amplitude

and the

duration

of

the pul.se

shaped

b]'

the

external

device

for

stability

preservation

and

fed to

the

regulat.ing

S-r,*c1**

cf

tire

turbine

via

EHC must eonsider the

gravitl'

of

the

fault

(type

of

short

circuit

and

its dura-

tion),

the prefault

conditions

(magnitudes

and

direction

of

pou'er

flou's

and

tbe

like), and the afterfault

conditions.

Hence,

the

"dosage"

of

turbine

unloading

must

be determined

by

the

conabined

anall'sis

of a

aumber

of

factors.

The

sama

applies

to the

automatic device

used for disconnecting

and electricall_1' decele-

rating

the

generators.

To solve this

problem

a speciai

logic device

is

needed.

With

the

aim of

simplifying

the

coutro]

process

the so-called

"program

con-

trol"

method

may be

used

in

which

a

precalculated

control

signll Jhaped

by

a

relay

device

corresponds

to

certain type

fauits.

I

CEAPTER

TOUR

comrnou

for

the

whoie sta'r,ion

t.0

0.9

0.

a.

(FiS.

t+-Zg4.

This

signal

acts

through

the

eleetrohydrauiic

converter

on

the

,Lgittrtiog

s5"stem

af"the

turbine.-Th6

coatrol

s"renal

governing

th9_11o.Tl

i'^q

e;il;;?i

""i"raing

is accomplished

in confo-rmit5r

v'ith

the extent

of

the

r - - - - ./t^- ^--^--l^

.i*

^^*-l.l^*^^ :';+L +h^ ,f omoo +n sthinh f.ho

e1tgfnal

OlSf,UIDaILcc

UUI'

eralruPrc)

rJ-r uurrrPrrd'tr't/r;

wrlrr luv

uebrvv

for.*,ard-sequence

noiiage dropi).'The

derlice

is single-actqng

without

further

"o"ttoi

of

ihe

process,

ihus

open-Ioop

regulatio-n

is

effected

"--fh;

t"pia

unloading

of

tbe

turbin-e

eniures

the

transient

(dvnamigl

stabili.tV

of

the

genLrator

due

to" an abrupt

increase

in

the decelerating

area

(Fig-

4-21\.

Fig.

4-20.

Open-ioop

pulse control

of steam

turbine

i

-

eiectrical

attachment

of

electrohydraulic

govennor:

1,

-

controi

action; APr

-

mag-

--

--rutude

of

pulse

silnal;

P

-

turbine

power

output

Tbe

relationship

Lretq,een

the

ehange

in

the

turbine

outp-ut

a-nd

the

value

^*J r---^+i^- ^+ +h^ --^roncrrlo. -rrlco iq dolprrnined hv the nrtlse characteristics

0

20

t0

60

g0

t20

tt,o

t60

,E0

Fig. 4-21.

Pou'er

characteristic

in

puise

brak

ing

of

steam turbine

,4

-

turbine

power

output;

A

-

generator

po\per

output; I

-

accelerating area

*"ith

three-phase

sboit circuit:

2

-

brakin! area

with

quick

pulsed

drop

of steam

admission to turbine. The arrow

sbows

how

power produced

by

turbine

tends to

recover

af tei renoval of

pulsed

limitation

of

steam

inlet to turbine

0.6

Fig.

4-22.

Puise characteristics

of

turbine

K-200-130

t-2ir,

0.12s:

2-Z ir,0.23s;

3-t'ir,

0.13

s;

4

-

4

ir,

0.23 s

lAP

.2

Asstglm.enl o/ A

o,

co

and

a

tor

decovznQ

of

command

stqfiol"

Fig. 4-23.

1,

b, c b1'

Control

pulse

shaper.

Operating

current

(*)

is

fed to busbars

the

elements

that determine

the

time of

forced

braking

of turbine

P

GeneraI

port

Pulse

sjgnal

execu

tLon

iAP-/

vZATP ^^

./L_JYLJ-!-!-

lAR

-2

^241P

t"*

CEAPTER

FOUR

of

swing

because

of

a

too rapid

load

pickup

on

the

part of

the

tuibine

aiter

its

heav-v-.

short-time

un

llil:liHl"ill"'""Jt*i#:il"#tT#{p;"by,"o*f

"'^H:h:-:ilT::""T"-:i

*

|3",ffiHil"1H##;;"";i*il1'

(nq

L:!)

:ry,,:lip:.:r-l:' ff""ii11;|

to',!-"-.Y1i",""i'^i:1"-;;

i;fi;;;i";s

7.

"nd'

?,

v'hicb-

are

the

amplitude

purse

$tEuar

rD

ucTruet*^l"-:-1

^- *^-*;^- ^+ iho

"ionel'

a^ and c detgrmine

thg

puise

sig3ai

iij

ueiJe'i:iiiiiivu

&'i

oil;

oo

and

t

determine

the

;;d

ib;"tt*.

ot

in.

iectangilar

portion

of

the

sig

,. ----^J L-- +L^ ^^-o^ifqnna in fho e.irerrit

3if,rlff

l'fli,ir"it'"ri"^;;1tiff;;,:ri;;;;used

by

t-he

capacitance

in

the circuit

and

thi

time

constant

of

damPing'

iliiJfJ"'.Hi;tTinT**1ffi

?'*'chaagedl-"l.Iltt].'"':ll-'.,{:'*::lt":::*;

tions

then,

after

:ffii-;il

unlo"ding,

thJ

output

of

the

turbine

may

recovet

AUTOMATIC

CONTAOLS FOR MAINTAINING

STABILITY

Union Heat

Engineering

Institute act

upon

the

speed

governor

control s-vstem

bp

varying

the fiow rate of the oFerating

fluid in

ti,e

puice

line

(*i*ir*)

*m-

necting_the

c.ontroller

of the

speed

governor

to the

governor

intenoaediaie

piiot

valve

(Fig.

4-2:c)U'

-6).

The

signal

to

control

the transient

proces-s

is shaped

b1'

a

rela.v attachment

+^ +L^ ^l^^+-^L,-l-^-.1:^ ^^---^-3^-

rFL:^

-rr- -L-- ^--

Lu LIIe

tsreu!I-uuYuJ-i1

ul.lu

uu!Yt}rLtsI

. I[tl.s

aLLaurrrrtellL ge[eraLes

a

rgclangular

pulse

o{

sp-ecified

duration

and a residual signai decaying

v-ith

time.

Tbe

iegu-

iation

is

effected

through valve

I which-open-s

the

return

outlet

for

the

driviag

fiuid

of

the

puise.

Iine

in order to abruptly

reduce the turbine

output.

The pick--

up

time of the

relay

attachment

is

0.06

s.

The turbine

outp-ut and the

por

ler

generated

afterfault

are equalized

by

regu-

Iating the working

fluid drain

from

the

pulse

iine in the

second

parallel

branch

of

the draining device.

Tiris

branch

has two

regulating vaives

2

and

3.

Yalve

2

opens upon

receipt of an

emergency signai.

The drain

is

regulated

b-v

valve

3

v'hich

is controlled

by an

electromecbanieal

follos-up

s1'stem.

The control signal

is formed

b5' comparing the power generated

after

the

fault

with the turbine

output

posrer

before

the

fault.

The

signai

acts

on

valve

.?

until

the

turbine

output

corresponds to

the afterfault pov'er

rn'hich

is sensed

b5- an

electrical

power

indicator.

The

fsfslefault

pos'er

is ciamped

bi'

the

con-

trol

vaive.

-

Figure4-26

sbon's

the

block diagram of the

electical

attachmenr

to tbe

ii-300-240

JIMB

turbine [a-7].

As it

bas

been stated above.

the

"e]ectrica)

input"

of

the regrrlating

s1'sten:

i-<

used for

a

tulnircr'

of purpc,ses.

enlergenc-l'

deceieratrng

amdng

.thq*,

Tbe*

units

?on

prlsing

the elecirtcal attachmint'assembll

aie cbnmined

n'ittrin

tt,.'Ouri[a

""iii"..

The

letters

HPP.

IPP,

LPP

denote the

high.

intermedjate

and

lovl

pressure

parr,s;

L.

rtFr.

trr'

Lrr

uErlur,E LlE

urgrr.

rrLerrl]eqtale

aDo

lo'til:

pressure

Darts:

rr,

-ald

n_8,_steam.pre_ssure

vaiues

inlhe steam

fiiled sosces;

r.p,'turlio;-d.i;;;

727

8, boiler:

rlr_.

ra, and lr.

steam

pressure

vaiues

inlhe steam

fiiled spsces;

fp,iurbin;-d.i;;;

leed

pumpj

€r

and.

ir,

H?P

ana

IPP

regnrlating

respec[ive]1'-r.a]r;es;

I',

and

T'".

valves

of

the reduction-cooling

units: ,SM, servomotors

of

val.ve-s.

[,

and

_Ei_f_G

turbogenerator.

tvpe

leed

pumpj

€r

and.

ir,

H?P

ana

IPP

regnrlating

respec[ive]1'-r.a]r;es;

I',

and

T'".

valves

of

the reduction-cooling

units: ,SM, servomotors

of

valves

E,

and

E";

TG

turbosenerator.

tvDe

Fig

4-24

--: --.1-^ -h"--

uom[lal]u

Purne

oDqyu

of

pulse;

z-traiiitrg

t

-

rectanguiar

portlon

o!

,.

pulse'

,: -;-^

-

rortion

due

to

eapaclr'or

o IscrlafilE

portlon

4-25=

Block

diagram

ol

electrobydraulic

attachment

TB8-300-2;

AG, auxiliarl..

generator;

I/,r.

vac.uun

indiiitor;

A,tSpt, main

iteam

j.1:

i""

-\:,Y

r

ou^rrJoi'r

EEIitro.wr'

r{:

Yd:,:uJ-lf

_ll.ltltudt"uL;

IvJDI'J,

tt14111

S[eam

pfgssufe

,i,sftolli,

"t

/.:

lPeeo

governor

pllor

valve;

DGvJ-{,.. sp€ed

g_overlor

-\i'alve

stroke

indicaLor;

termine

the

amount

of required

unload-

'

station

as

a

whole

can

be

unioaded

by

operating

in

Parailel'

q.PL

opeiation

is usually

preceded

b-v

systed,

however,

noal.be

buiit

as

an

I

turbine

output

accord

ing

to

the

af

ter-

lrall-v

trsed

as

the

actuating

element

of

lic-po*et

liniters

developed

by

the

AII-

tlrolsaLor; ur

/.

speea

governor

plroI

varve;

DGvi-{-.. speed

g_overn-or

-\i'alve

stroke

indicaLor;

{P1,

intermedia-t,e

superheater

steam

pressure

indicator:

-r?8,

hldraulic

bocrst.er:

Eltf

C'.

eiectromeciranicai

converter;

3'It|A. sudmrng

magnetic

ampiifiei;

.FC, functjon"i

c,onneiier;

P.1,

power,

indicator;

.l-U,

freguencl. unit; and

DIF. diffeientiator

connected

either

to t[e

inpuLof tJre.

strohe

indicator

of

.the

spee.d

golerrror

or to

tbe

output

of

tbe

freguency

unit_

The follo.*'ing

signals

are

fed

to

the

-eiecftical

attachment:

.

(a)

Current and voltage

of

the

turbogenerator

from

tire

jnstrument

transformers

to

the sensing

unit

of the

power

indicat.or.-'

(b)

Signals-from pou'er

indicator

Pl and

pressure

indicator.SPl

oi tbe

jntermediate

liiPerheat'er

to the

input

of the

device

for

shaping the.

signal

of.initialirreguiarity

"ot"".iioo.Tbe

latter

devjce

forms a signal

proportionai

to

the initial'irregulariiy

coriection

(JIC)

K

!'2 ri,2

iic:T;--T;

s'here rr

:

relative value

of

generated

porver

,,c ,,Tr:

relatjve vaiue

of

,the

steam

pressure

in the

intermediate

superheater

1/6N.

.ltq;.:

ste.am power

and_

pressure

'regulation

tacto".,

[sp-e&i;.iil"

. .(c)

Voltage (freguency)

of tbe_canier{reguency

subexciter

AG of

thL

generator

. .(c)

voltage

(freguercy)

of tbe_canier{reguency

subexciter

AG of.

th-e

generator

itation

l}'stem_or _thq.llgnat

Jrom the

speed

governor

valve

stroke

indicator'SCySl

to

input

of the

DI F

differentiator

(acceleration

transmirt,er\

exc-

the

VI

input-of^

the

_D/F

difJerentiator (acceieration

transmitter).

-

1d)

signai

from the

main

steam

pressure

indicator

r,ISpI

and vacuum

in the

turbine condenser

to

the

inpui

of

the

protection

device

ioull

stl.gnol

To speed

Q0vernor

thrbuqh

tnler

mecitdte

pilot

vatve

Iron;rcii!

Prace

s

5

cont Ia!

and

7et;ovinQ

attachneii

ELeci

ra

-

indicator

r

AUTOT1ATIC CONTROLS

FOR

IVIAINIAINING

STABILTTY

129

CIIAPTER

FOUR

!28

Provisiosis!cadeloradditioDaIi!Putsigtals'romtheextemalautomaticdevieeswhicbi;ir,fii"*:tRtf"$t.,::#?*ti#;a;"j*;iTHs'1TT}.1f*.#'s''an"'ir'lr

ilHHffi

ffi* l'^-":g":,1"

g:is

il

jt',ii"

"ffi

li,'*f

'"

ll;j*$f

"ii'

4-5. Automatic

Devices for

Sectionalizing

Power

Systems

to

Prevent or Eliminate

Asynchronous

Operation

DiJferent

types

of

automatic

sectionalizing

devices

are used

to

suit the

specific

operating

conditions

and eonfigurations

of

power

systems.

When sta-

Uitity

dislurbances

cause

no resynchronization

(for

example,

s'hen

dis-

connecting

large-rated

transmission

and

when operating

the

power

system

com-

ponents

through a

small

capacity

tie

line)

sectionaiizing

automatic

devices

Fig.4-27.

Paraliel

operation

of

po*'er

systems

over

two

tle

lrnlis

Fis.

4-26.

Block

diagram

(electricai

attachment

of

automatic

control

system

of

turbine

K

300-240

"^riil""t-

"o"t"i"*a

I'itliin

the

dasbed

outline)

providing

the most

rapid- response

are

appiied.

If

there is a need

to

cheok

a

resynchronization

possi-bility, it,

is

bet,ter

to utilize

sectionalizing

deviees

which

operate

if

asynchronous

operation

continues

ionger

than

a

permitted

period.

Let

us consider

the

operating

principles

underiying

various

types

of

sectio-

nalizing

devices.

(a)

Automatic

seetionalizing

devices

of

instantaneous

action.

Described

below

are

several

versions of such

devices.

1,.

The

most simpie

variant is

the use of current

reiays

with

series-connected

contacts

in

tbe

A,

B and

C

phases. The

low

probability

of

three-phase

short

circuits

during

which

these

devices

may

misoperate makes this

variant

suJ-

ficientiy

reiiabie,

especially

if

the device

is used in

a sTall-power link

by-pass-

ing

an often

heavilf

ioaded

link

large in

rating

(Fie.4-27).

-

However,

the above

variant

performs an unwanted

sectionalizing

operation

even

with a

successful

automatic

reclosure

of

the

powerful

tie

line.

9-2076

staqe

can

be

accomplished

by

rectangular

p!is$

exporentiallv

decaying

in

time'

The

second

and

third

stages

ma-v

have

a

rectangui"t"ft^ii"g-'"[gt

"*Jbe

-c#cefled

after

a specified

CEJ.PTER

FOTIR

AUTOMATIC

CONTROLS

FON

MAINTAINING

STABILTTI-

131

r30

alizius

makes

even

short-tim

e

asY

nchrono-us*op:tt*:t:

tbe

above

instantaneous

sectioualizins

automatic

circuits

*"y

*r'Jf,"tftt*

-*ith

the

operation

of

g,

one

ciirrent

relay

connected

iit

pUqry

:

gq

be

used.

Such

L

of

the

ratiu

device

:r**;"i,"rr3s";.,xF"rH:rff

:T"ffi:lIJ,."".;[";iiiiiJa!"r*.n_".{:^,-*j

sectioualization

afkf

ieverai-

"w"tito"o"t

"y"Ies

rat'her

than

iastantaneousty'

rhe

instantaneous.response

*-:i4lifi:-iii,::*",ffi*

"l"J,iJ'"H"-.'"'."|",i

3;":ff

:.

""l"ffi:"i

trd#:

J-;i'

i t'"

"

;'"

miil

i*,,";:ltng

a

ga

in

st

succe

ssiui

op'eration

of

the-ARC

hevice

on-the

"powerful"

tie

line'

-

prevention

oI

hearry

voltage

d;;Pt

It

"

a""itive

f

actor

when

many

important

consumers

are

sited

"io*

to

the

iiectric

centre

as

voltage

drops

aftect

their

curs

near

the

location

of

the

protective device.

In

many

cases

the

undervoltage

t4_ay

with

a

|ow

pic.k-up

setting

-imparts

orrrnmqria

-colontiwftw

t.n the device- The sectionalizins

devices

nav

function

q

ulv4s!r

on

sections

close

to

ibe

electric

centre

q'hich

often

is the

midpoint

separating

iU1

po*.rs

(the

zero

flow

poin!).

A

heavy

voltage.*loq

occurs

at

the

eiectric

centie

when'the

emf

vectOis

are

apart

more

than

120 degrees.

Z.

Using

a

real

(active)

power relly

gives another

variant

for

instantaneous

automatic

Iectionalizing

purposes.

The

ielay

may

be

a

three-phase

forward

se-

l,tro""

device,

or

inclute

three

siugle-phase

relays

n'ith

series-connected

con-

tacts

having

a

pick-up

setting

Ppicr-uF_:0._8

P*q"-

(see

Fig.

lll-

This

auto-

matic

devic[

funttions'when

tEe

angle'6

is about

60

degrees.

For better

isola-

tion

of

the

automatic

control

againJt

sJ'nchronous

su'ings

and overl,oads

(*'hen

no

as-vnchronous

operation

arises)

_its-

operation.is

usuali-v

permitted on)1'

after

dir.ooo".tion

of

the

high-power

link

lnd

if the

Pg-wel

it

transmitted

before

the

lault

would

cause

stibilit-v

disturbances

when shifted

to

the low-power

iink.

Dir"d.o"otage

of

this

variant

is

the

use of co-mplicated

reial's

a-nd

tbe fact

that

their

operat-ion

depends

on

the

value

of

voltage

at the

installation-

point..

As

t.o

the magnitud.

'of

thr

transmitted

power,

the

-critical

velues of the

settings

siiould

be

"oriented

towards

the minimum

value

of

tbe service

voltege.

3. The

thirC

vaiiarrt

of

the

instantaueous

sectionalizing

devices

uses an

inpe-

dance

relay

(resistance-reactanc€,

or

directional)

as a

detecting

element.

As

**f"r"a

io

in. current,

voltage

and

active

pow€r_relays.

tbe impedance

relay

makbs

better

use

of

tire

overloading

properiies of

the

tie links,

since its

opera-

tioo *or.

cleariS'

clamps

tbe criticai

'rriiue

of 6".

at

wlich

the-.power

carried

bythe

tie link

mtst

beieparated.

More

than

that,

it'

"self-adjusts"

to

the

before*

fauit

vaiue

of

the

voitage.

One

simple

automat-ic

sectionalizing

device

eaploying

impedance

relays

io o1,^-,- i- Fia l^R, Tho.'irnrrit ic, sirnilnr t.o t.het, nf the automatic sectionalizins

IE

JlVnU

ru r r5r

T

device

considlred

earlier.

The

use of current

reia-vs

prevents misoperation

of

the

device

due

to

a fault

in the

voltage

circuits

and

rn'hen

asymmetric

external

short circuits

occur.

When

usiag

a short-circuit

cunent

protection

system,

tbe

sectionalizing

device

can

be

6asil_v

made

from an

impedance

relay

(resistalce

and

reactance,

or

d.irectional)

emploi'e{

as

a

starting

eiement

with pro-perl-v

chosen

pick-up

settings.

The

best

^operating

results

aie

obtained

when the

device

is installed

at

the

substation.

near

the

electric

centre.

4. The

above

described

types of

automatic

sectionaUzing

devices

function

when

short circuits

occw.

As

mentioned

previousll', special

rneasures

mrst be

taken

to exclude

unwanted

operation

and

clear

the after+,ffects

of such

gpera-

operation

of

instantaneous

sectionalizing

,se

ones

included)

a circuit

may

be made

s

when

swings occur.

rlied,

the only

difference being

tbat

in

,ck

causes

the

protection

swten

to ope-

9*

oroduction

Process'

"'"i*otoving

the

resPonse

of

a"ui[i

to

t[ree-Phase

short

I

'!Q

!-'!atrirp fnr nuick

tripping

in

asynchronous

operation

llE'

'!-/'a'

uEYrw

rvr

Ye-

tbe

ARc

flsrrice

which

isolates

the

automatic

sectionarizing

devices

and

recloses

the

sq,itcb

r*,hen

ifi"*

f.

"o-voltage;;";

the

rliscon*"t.a

fne

side.

If

the

swilc!

has

an

ARc

a.'J*-*uich

does

noi;;;idt.lU=:I..-'-l:"iEl9"::'"ttyt-"':-:f;

r !-- ...i+},^'rt o*r',r.hrnnism-cbecking

equipment)

trne./rnu.^tY"'o.-T:..i-",-

;ing

del'ice

tunctions'

tJlnerwrse'

ururLr-

conditions.

Toimprovetheautomaticcontro}Igspgnle'andobtainbetterisolationagainst

ro

a

d

currents

tuelciJci,ii,U.

"ra

bt

;;;

;ili;

*1

t1

-"f

i"

a"t

uott"

ge

rela

v

(F

i

g' a-

28)'

If

the

setting

of

a

relay

counected

io

the

voltage

u"c

is

lesi

than

40

per

cent

Disconneetzon

132

CITAPTER

FOUN

rate

during

s

IXTJ"#f'#';";nJff

i"'"""ti"n;-'-:l::::"^".:ti,1l-*Jl;lTtr:f

',"J*

lJ'tt:111"#""JiH"t"":::";;;'i;:"1"il:;!ql'ie1:::*:::l:1,-:=v""h':-

lY:":::fi:: -:"#;;,Jr"

""a-iiot"

rc

themsel

ves duiing

short

circuits'

flutlD

wvrarlrb

rF---

r--

I - __ _r: ^--l:-i*^ r{orriaa

gThnqp

o'

idffi

?-*"'ift

fF"#'H:"*H:,:t;:;:':r":"ty;t*;i':##:::LTl;i';

'=$ffi

fr

?{i*#ni':f,.*x}*"T:1}S:l'ff

il:1"'i'":'ffi

:,i;Tfr

$i?g

I|fJ?J,t:,1,;"u:,",Jii#;!;Ti";;ia;;whenthisevariabressudden]vchauge

iiOic"tiog

a

slrort-cireuit

fault'

APC

prohibiting

F!g.

4-29,

Ingtantanecus

seciionallzing

devir:e

J

-

more

,"riiti"t

reia}-:

I

-

less

sensitive'

relay;

J

-

auxiliarY

relal

Shown

in

Fig-

430

is

a

d'iagram

of

i.".tltoT.1!it^:t::1":1*T5:,iT:""'#llit

""":l;H;'i";'i','ril'h"'ilt?ffi

;-il'.::il*':*)J.-'"3:.:.:iJl::l"l':-:I;

I;dulIUv

vyvruvY

1 --- -^ A*i^AF aaton

iis

circuii

wben

elec'trical

magnitudes

oI

'bacx1"to-o-1::i:j::"-"#:""1""1;;'

;;;:

its

ctrcurr'.*":t;1"::::::;-5;;;""

cprr,)ene,es. anoearine

in

the circuit,

indi-

fOf

an

ltrSEanl.

Ilrtlllrp_utr:uLr

vr

vuvs"

":.1:;:^.l:::r

v

lur

us

^'

"

r - - l- -^ -^^+i^nolioof inn

cate

a

short

circuii

wBrcn

neeos

rio,stit'uiuui^'^":::-":'

ditl':i'Ti;iJilTi-',C:4:.**:1"::,,"-p;*Jig"l::X'J""';-.13-'l1il

,

"

u'i,l'

ii'#

illii

ii

li"H'

uii

*

"'

o

"I

{i"'y

*- :YT

s',

i-1

"i,

# ii: i S l" * ii:

::#"'#:;KH'Ji'-'"*"sl"."i1gT,i':l;*,'"tL;*::'*tlg.tlTTJ#,,':;

asllncniorlous

uPt

uosti"t

va"Iues

between

the

emf

vectors

of

i;;

of

a

relay-responding--to-

tlt

r --^r--- L^--:*- +1,^ *^'^nrinc r^nrrre

rnachines

op"r*tiii"*'itt?riti."A;t

,:ype

of

relay

ha'ing

the

folion'ing

torque

Contoct

ol

swing

bloc*ing

^.,t^.,* --1n,, urlh-ro.cl affer

i7 Y."' t' ; ;:, i";' i i ; ;

-

i

i ii

I

"

iiti,

"tii'i-iircutt

Fig'

4-30.

Instantaneous

sectionalizing

device

(o)

eontact

ol output

rela)'

to block'ae-ail:t

rr

sering;

(ur)

-

potential

to close

circult

of

rclaT

lAni @)

coittirii

ot

output-reiar-e-iobtocl

asain€t

i'

swing,

(uc)

s'itb

reeet

Iit

i'il"ciii.d'

time.

''fi:i#jjfT,i;"Ii#li,Iti*'in"S,t:lg|

I

-

contact

ot startlns

CJ

\

o

(J

a

s

qJ

\

s

H

N

can

be

used

where

Ur

and

M

-U

rUzcos

(cP

f

a)

{J

z

:

vo}tages

aPPIied

to

the

coils

d

:

"osi."

I,etdrli

ll._ J^.r-t^",1i."r

(4-26)

of

the

relays

U,

and

U,

'flP

I

:

int"eroal

angle

of

the

relaY

rrn nnlnts M and

l/

of

the

Pow

Ii

voltage

tro*

polnElr

"of

r'/

of

the

power.system

(Fig-

z'-3t)

(from the

nts ro

which

tne

eilTis

t;

;d

E,

a.re

qlpti"a;

is-fed

to

!tr,e,rel"y,:T]irlli:

p"iilJ;JT1"t,i'",f,*:3*;

t;f

i

E'

::'-1pJ:::*1,\1:'"*":"-iif #TIti';.f;,'H:

*ii"T#

ix;ffiffiti.^""

:'e0

;"si"''

tt'"

'93v,l9'g-Y-:*l

*i:Il

g'#

:*:

wrtn

lne

rulurudr

d'Brc

e

-

vv

--"otultt*s

with

the

internal

angle

a

:

0o

the

angle

0

:

I

----0

and

180

degees'

- - on --i s?n darrropc Thrs if *se is

1,,

Ip,

6

F

{.r

R

Sr?T

ffi#

iiir

f,,

"*i

*f,""

6'

:

q

-

s0

and

270

degrees.

Thus,

if

use

is

Fig.

4-31.

Power

system

7U

CEAI{MN.

FOUR

AUTOMATIC

CON?ROLS

FOR

MAINTAII$NG

STABILITY

and

Hence, if

the

so that

and

made.of

two

r9_I.ays

having_different

internal

angles,

a

certain

tact

closing

w'i[

correspon_d

to

a

certain

change

6t th"

angle

6

The voltage

at

poiut

P

.

t,'r-

Er- i

r*r*,

1

U

r-

ir-

i

rnzn,

I

voltage

trom

the

substation

P

is

impressed

upon

terminals

of

an

auxiliary

synchronous

machine

mounted

on tbe

generator

rotor

shalt.

The

above

device

operates

only

at

a

certain

amount

of

slip.

For

this, the

output

circuit

must

include

a

tirne

relay

and

au

oprt*iioo poG"

counter.

The

time

relay

allows

the

formation

of

"o

oulpot;ig"*l

at

a certain

duration

of

the

output

sigtal

generated

by

the

counter.

Fig'

4-33'

Coanection

af

relai.'

in

device

detecting

&s:y-neh-rorous

operatioi

J'8-poiarizecrelays;J'6-rectifi.ery;

.z,r-interven-jngtrarLsforEelE;9-resistor;

tc,

_

capacitor

to

adjust

iiteinat

ahit-t-a;;i"

ot

relely

j-pF-

sequence

of con-

in

time.

(4-27)

the

relay

(4-28)

the abovg voltaoes will nnrr.oennnr{ fn fho -'o1,,^o ^f J ^*,r

"l

'TrL^

---r. -^ r--

__--o__

yv

uuv

vqrueD

".

al

d.uu

{rZ. rItE

vUILage

(IIOp

:trFncc fho

in-orlon^oc.

^-,1 -

:^

^^* r-J L

uuv

^sHvuquvve

bMP

attJ-

bryp rr

ttu[rPEr]satg(I

oy a

curlgnl proportlonal

to

Ipa

<-_

Ipu

-+

Fig.

4-32'

Operation

of

device

detecting

asynchronous

operation

Ices

zt

"q,

:

.'kfue

and

z,

eqt

:

kzz

xp.

zt

"q,

and

e,

esu

is

added to-the

voltage

r

transformer

VT

(Fig.

4-32).

Such

cii-

I

to

unity the

voltage

drop

is fuliy

com-

)

is greater

than

unity

oveicompensation

,)

is less

than

unity,

undercompensation

The

device

for

-detecting

asynchronous

operation

must be

discriminated

against

the

effects

of

a short-"circoit.

Io

this

instance,

th;utpJpoir.

is

formed

z,

"gu

z,

"qu

after

a

certain

alternation

of vectors

E,

and

g"

w

o

,

i.e.,

whetr

synchronism

is

lost.

If

the-device

is

Under

norma]

operating

conditions

(Fig.

4-34)

the vector

E,

Ieads

the

vec-

tor

E, by

the

angle

6-

(it

is

assumed

that

the

generators

deliver

power

to

the

power

s1'stem).

In

sucli

a

mode

of

operatioo,

"o"ot,

c1s

Z

of

the

relays

.Zpfi

and

2PR

(Fig'

a4!a)

are

closed..

The

areas

within

wnicu

tn*.o[r"-6-varies,

r,hile

contacts

'Z

and

2

of

the

relavs

IPR

and

LpEr"iiin

closed,o-"r"

shaded.

Since

the

contact

lAR-L^is

closed,

r*..ot

fiowslo

tn.

"oil

of the

iustantaneous

auxi-

liar-vrrel3

\'-24R'The

reial'iaR-opr*

contact

2AR-z

and

closes

contact

s zAR-I

and

2A^R-3'

The

contact

-zAR'-3

pr€pares

the

output

circuit of

the

device

and

:lj"::1tf:r^1!:J,"t|lcjrcuii

uiail.s

i[.lrr"v7e

R

gfter

the

reray

ppR

has

"t'ri9n:*.o"oj'iflt^:::.^;:-rt;;r?;i^ift

ri?;;d-i;rlh,:;""hlr-ifa$',

of"

relay

1P

R

opens.

Is indic"t*a-

"1"J.,

rh.

;-;;

zA

R

still remains

closed.

AJter

the

angl_e-d.\s

passed

tne

r-g0

a;s;.

fti;;

and

ues

q,ithin

1g0_270

de-

grses

contact

J

of

the

relay

-IP,R

closes

to

s.nd

an

output

sigral.

as

the

arg.te

O

installed

at a

power

station,

one

of

the

voltages

may

be applied

to

it

from the

'"?tFF

*

136

CIIAPTER

FOUN

increases

further contact

J

of

the relay

ZPR

aperrs

and

deenergizes

tbe coil

of

the

relay

2AR. Thus,

the

circuit

is

prepared lor new

(repeated)

operation

after

the

angle

6 has

passed through

360

degrees.

If

swings

do not

make.

the angle

6

exoeed-1$O

degrees,

i.e.,

the synchronism

is not

lost,

the

output

circuit

is not

closed.

The

circuit,

also

does

not

close

when vector

.d,

t"gt

vector ^dr.

The

device

can operate

properlv

also wben

the voltage applied

to the

relays

/Pfi and.

2PRisnot

exactly compensated

byfor

the voltage

drop to the

points

to

AUTOMATIC

CONTROLS POR MAINTAINING STABIIITY

In

many

instances a simpler

device incorporating

an insbantaneous

current

relay

and

active

power

relay

may be used

as

a syrrchronism loss

detector.

Sln-

chronism

disturbince

and aL augle

6

in excess

oi

180

degrees

are characterized

by the

chauge

of the active

porver

poiarity

along the

line

when

the emf

vectors

are

parted by 180

degrees.

The

schematic

diagram

of

a

device operating on

this principle

is shown

in

Fig.

&35.

To

prevent

possible

misoperatiou

due

to

changes

in

power

fJows

at

short

circuits

and after they

are

cleared and also during

sbort-circuit

discon-

trol pulse

generated

by the

device

.{s1'acil;o_nous.

operatiorr

detecting

device

s'ith

a

real

pou-er

relal'

actuates

a pulse

number

counter.

Sbornt

in

Fig. 4-36 is a

circuit

including

a

two-q'av

power

relal'

P

q'hose

jeint

operation s'ith

current

reiay

C.R

v'orks

out

the output

signal *'hen

the

angle 6

passes

the l80-degree

region.

oJ the

out,put relal'

3AR

becomes

completed.

The

latter

func.tions

and injects

the

output signal.

If

the

device is installed

at the po\^'er

station

delivering

power

to

a

power

system

and the loss

of

s-l'nchronism

is due to the

fact

that the

emf

vector

E,

of

the

station

generators

leads the

voltage

vector

iJ"ot

the system,

then

tbe

contact

P--Z closes

initially

and,

after the

current relay

C,R has

functioned,

the coil

of

the

auxiliary

relay lAR

is connected.

The

contacts

of

this

relay

prepare the

circuit

to

close the

coil

of relav

3AR

ick up after

the

vector

E

"

is shif-

m the

oeb area to

t

area),

open the

coil circuit

of relal' 2/

(b)

Fig. 4-34,

Device

for

detecting

asynchronous

operation

(a)

relay connection

diagram;

(b)

explanatorx

diagram

other

through 180

degrees

during asynchronous

run, a lact

which

does

not' occur

during

synchronous swings.

Diiadvantage

of

this device

is

that

it

is very

complicated

^and

pro.vision

s

(by

the

above-nentioned

interlocking

units

br

the

use

of an

opera.ting

pulse

lo

puLse

counLer

cu

resy

n'chron

i za

i i

on

uni

I

tippaiatus

z

270'

cortact

lAR-3),

and

ensure

self-holding

of the

circuit

(through

contact,

lAR-1).

After decreasing

the equalizing

curent in the

270-360

and 0-90 degree

regions,

lr

ELz

Ll

-z

(a)

(by

the

above-nentioned

interlocking

units

or

the

use

ql

an

oPer

counter,

the latter

rules

out

instantaneous

breaking

of the

tie link).

CEAPTER

FOUN

AT}TOMATIC

CONTROLS

FOR

MAIN?AINING

STABILITY

139

the

relay

{ft.gp.ry

its

contact

to

reset

the device.

The

LAR

relay

functions

re-

F_"LqJ"*.

whether

tbe

stability

is

d"isturbed

iu rhe

_power

sysrem porti

garoress

w&elEer

tDe

staDUlty

ls

disturbed

i^u the power

system portion

that

i:"F

power

or

in that

which

has excessive

power.

If

'the

coniact

cir-cuit

of relavof relay

3AR

is

cootrolled

by

the

contact

of

relay

iAR,

which

is

closed

after this

relav

IAR-I

has

operated,

the

output

signal

wiil

;

be formed

when

the

stability

is dis-

trubed

due

to

the

lead

of

vector

^E'".

i.e.,

because

of

excessive

power

at tlie

sending

station.

The signal

may

be

used

to

execute

the

'LESS"

command

or

to

disconnect

part

of the generators.

It should

be

kept in

mind

that the

appearance

of the

sigaal

will

not pre-

vent

stability

disturbance

(the

s6bi-

iity has

been

disturbed

as the

angle

6

is

in excess

of

180

degrees)

and tbe

srg'uar

uray

De useo

merely

lor

suDse_

quent

resynchronization.

(c)

Sectionalizing

devices

*-ith

swing

c-r*cle

counters.

The

automatic

sectionalizing

device

operates

after

'

tbe siariiug

element

functiotrs.

a.

cer-

tain-

number

of times.

This

simuit,an-

eously

protects

the

operation

of the

automatic

device

against

short

circuits.

The output

rela_v

functions

after

seve-

ral pulsations

of the electrical

quan-

tities

causing

the

contacts

of the

start-

ing

reial'to

close

alternatell

.

The nun-

ber

of actions

and

the

cuuent (voltage)

oscillation

period

at which

the

output

phases

and zero-sequence

current.

The

r

Fig.

4.37

sho\rs

a

circuit

variant

in whi

_

___ ___D

rent

rela-ys_

is

connected-

to each

phase

cond.uctor

of thi

line.

I

po+se

of the

starting

element

t-o

asSmchrooo*

"u"rents

and

lation

fg:ainst

load

cirrrents,

the

stariing

eiemeniotten

utiliz

tage

relays

and series

connection

of thi

contacts

or t[*r"-"J"v..

. ]ht

experience

gained

from

the

service

of sectionalizing-devic"s

furnished

with

a

counter

for

the

operation

cycles

of the

rtrtti"g

etemEni

has shown

that

a:

G

,.

.b

Fig.

4-37.

Circuit

diagram

oI

a sectionalizins

device

lol

their

design

must take

into

account

the

multi-shot

operation

of

lightning

arr+

sters

durins

intersive

thunderstorm

disturbances,

current

and

uiti"Ju

-r;;;,

due

to

shoit

circuit,

its

clearing

*"J

."ur"qu!Jt

line

reclosure

b5,

the

ARc

device

where

the

short

circuit p-ersists,

etc.

'

The

circuit is

designed

to

send.a

disconnecting

puise

at the

third

tiip-and-

closure

cycle.

The-output

relay

7AR

funsiio"r

"it.i

the

prescrilea

number

of

operating

cycles

of

the starting

element

is

accomplisiied

"ia

U the

time

durin!

which

the

starting

element

conlacts

remain

open

dles

not

exceed

the

rated

value.

In the

case

of

exiessive

time

the

device

"r"Jt..

ine

o,rmber

of

trip-and-closure

3J!1"-t'.

usually

from

th-ree

to

six,

is

determined

by

th;;;"ttni'lete"tivit.v

of

the

automatic

sectionaliz.ing

devjc-es

*g{

io

the powe6yste*.

?n"-ir*"

l;lry

ZR

is given

a setting

of

2.6

tu

2.5

s

which

rr.rJdr

the

tim.e

the

line

breakers

remjin

opel

r{r

the

automatic

rec}osure

cycle.

.

Figure

L38a

shoq's

chaages

in

the

s_tqtrtrg

element

current

as

it pulsates

3,H1i_-'.{::}:::iTj:ilill 1p"iog

oi

l.

ri"-Jpen_state

rime

oi

th.

srarting

Fig.

4-36.

A.synchro-nous

operarion

derecring

siglll

tj

ploq"qed

.

are prqeJ.

elernent

made

up

of curreit

ana ieil

po*".

re)avs

Mechanical

devices;

rapid-response

auxiiiary

relavs

and electronic

devices

(o)

scbenatic diasram; (b)

explanatory

diagram

may

be

gsed

aS

CyCle

COUnterS.

COUn_

element

contacts

employed

.bv

tur

automatic

sectionaliri"g

d*i;

#;".

p"iJtE

I,

2,

7

correspondio

thd

pickup

instants

of relsv.q lap 2a R ca Fl

the

counter

is

also

-triggered_with

stability

disturbances

in

operation

with

in-

cono-plete

number

oI

phases.,This

condition

is best

met-by

"otr'or"iittg

tbe

relay

to

the

current

of

pbase

conductors

A, B

and

C or

to

the"eurreJoi

oor or

two

rg.

&3UD

illwtrates

how

the

current

chinges

in

case

of

a

short

circuit

cleared

within

tifre

(r

rg.

4-Jl).

ment

circuit

in

the

starting

ele-

ls.c.1,

line reclosure

within

time

f".

".

by

the

ARC

device

after

time

fapa

and

repeatea

tripping

t40

CEAPf,EN FOIIN

The

oppratiug

time setting

of

the

relay

?fi

(Fig.

L37)

11 must

be

greater

than /",

but

less

than

f,16g.

(d)

Sectiosalizing

devices eontrolling

asynchronous

run

witlin a

specified

time.

A

power

system is

sectionalized into asynchronousl-v

operating

parts

only

when

asynchronous

run

persists

beyond

the

preset

time.

The

use of such

devices

I nA ^L----- :- tl--:-- :- aL^ ^:-^--:a -! -.--.:-^ ^l^-^-a ^t

rIg.

e-oo.

uuan8'es

lI1

{.rurrtsIrL^jr.Ylj:rY_,r_"^

lrl_t-.^"jr""rt

ur sl,iuLrrB

rrrsllrExL

ur

d wuLjuldrrztu6

usYrvg

(a)

in

asynchronous operationt

(b)

in

ARC

operation

witb a

pereieting

short

circutt

al,lows

various units

instalied at

different

points

of

the

power

syst.em

to

be

dis-

criminated

in

time.

Jt{ore

than that,

be u-sed

only

after the

otber methods

of

the

power svstem.

it

enables the

sectionalizing

technigue

to

have faiied

to

promote

resynchronization

la.disconneclina

vilh

"a55sstJ

spf

A?t

.o-1

0'

fron

lJ

+

l<l

+-€

sig

/1SP

llo. /

c

0

fnn

VT

A/0.2

tvR-l

2vP-/

'yP-t

+AR

4-39.

Sectionalizing

device

with

asynchronous operation duration

cont-

Fig.

Shown in Fig.

4-39 is

a

rolled

variant

of

the device

circuit.

The

power

s5rstem ls

v,

ry,

7TR.3

lripptna

n

osvnchronous

opem{ton afier

ttme

'assieneC

6t'

settno

oI

relau Jllf

-z

Contro/

o/

as

vnchroocus

operatton

Eumtion

and reEet

Stqzal

on

operation

o{relays

678

and

77R

sectionalized

in

case ol

long

asynchronous operation

which

continues

in excess

9AR-l

.<

s

gAR

ser I

oI the ttme

perlod

set

on

U

ses

the

relay

-I.A.R

and then

relay

lTR

eontrolling

the

v

zl

17.

uperatron

ng

etemen

rela],

zAR.

The

latter

remains

closed

until the time

su'ing

period

acts. The

relay

ZAR

closes

the

relay

gAR.2

-

> APC

prvh,

Fig.

4*40.

Sectionatrizing

der

(a)

comltned

diagram;

-(a)

derelopedrrdiagra

f,ton or

gwt

ili

t

inq

Disconnactinq the

Iine;

ARC

pi'ohibitzag

ruce

ln asyDctrronous

opera

E'. Contact

positiorB

correspond

relay

coilE

tion

to

deenergized

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

Подождите немного. Документ загружается.