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

Performance

analysis

of distinct

controi

systems

ins

n'ith describine

the

paramet'ers

of

the

s_ystem,^means

investigating

the

process

differential equations

and

finding

suitable

coefficients

for

the

characteristic

eguatiol.

However,

the

fi-ual

adjuslment

of

tbe automatic

control

syst_em

used

to

control

a'power

s-vstem

is

carriei

out

experimentaiiy,

as

maihemaiicai

eguaiions

cannot

aiways-tiesc-ribe

completely

the operation

characteristic

of

a

power

S],stem. Therefore,

when

furt-

her

discusiing

control

devices

for control

of

the_ power

systems

u'e do

not

reguire

detailed

mathematical

analysis.

The

above

definitions

and characteristics

were

introduced

in

order

to

impart

some

idea

of

the

processes

occurring

in

certain

elements

used

in control

equipment.

I-4.

Relays

and

Relaying

Devic.es

ticn

of

the

+"ripping

mechanism

in case of

direct

ac'tion

relal's).

::

The

eiemenf

whiuh

introduces

a iag iri.the

relay operation

is

called

the

delay

neumatic,

electromagnetic

or

electrohydraulic

apparatus,

vacuum

tubes,

semi-

conductor.r

-1_4?::-a

:J:l"l:'^:.1.1J]1"^If

':,Il::'.:::::l:"q,:':*l::"-1'""":?

factor

effect

is

multiplied

many

times.

If

this is so,the

relay

involved

is consi-

dered

to

be

an

amplifier

with a

high

gain

factor or a

trigger.

Like

in

the

protective

relaying

devices,

the

rela-vs empioyed

in

an automatic

control

system

-controi

mainly electrical

circuits.

The actuatiug

element

can

act

on

tire

ciicuit

with

or

without

contacts.

As

to their

function,

the

reiay contacts

are

making,

breaking,

double-throw

oI

impuise

(variable)

bontacts'

Relays

may be

of a

two-position

t-vpe

in

u'hich

case

the

state

of

the

actuating

crrctam /olomonf\

rnarr

ho

oithpr

nncrrt.ivp

nr inoncratirtp.-

and of a multiaosition

JJ

sues

\v^vlgv^r

type

when

there may

be more

tban two

positions

of

the actuating

element,

dlpending

upon

the magnitude

of the

ext'ernally

act,ing

factor.

INTRODUCTION

If

the

actuatiug element and

all

the

working parts

automalically

return

to their

initial

nosition

when

ihe

extern

TIw drop-outua.Iue

Pa

is

the

maximum

magnitude

of

the

externai factor

which

causes

response

of

th-e

detecting

element and

makes the

actuating

element per-

form

the

reverse

of

the

pickup

operation

Thc

reset uaLue

P,

is

the

largest

magnitude

of the

external factor

rphich

causes

response

of

the

detecting

element and

makes

all

the

elements of

the

relay

return

to the

initial state.

reset

-

pickup

ratio given

bl'

INIRODUCTION

ZJ

D

ftr:fi

rp

Nowadays, there

are man]'

methods

which permit

the

,{,

value

to

be appro-

ximated to

unitf in t'arious

reiaf ing

devices.

This

adds

to

the

sensitivity

of-the

detecting

elements.

The

relays are distinguished

as

the

relal's

tha.t

responrl to

current, voltage,

impedance, po\!er,

etc.;

the

reia-vs

responding

to

the

duration

of a

phenomefon

(timing

reiays);

the

rela-vs

responding to the

seguence

of events

(iogic

operation

olomonlc\'tlto -.rlc^ 4-a-'r^-^-' -^1^-'. /^^"-+i-- ,i^,-i^^^\ ^+^

r

vue

IJu^ow

r^eyuelvly

rersJD

\uvtluurJ'tS

LrrtytrJtt>/,

titu.

Bpqidcs t,hp rclevq arp rlicf.incrrichod h'r' tho rqnda nf -rran{itr-

"o'l'o.

-,-l^i^1,

tbe

detecting

element

responds.

These

are

"over"

and

"under"

(maximum

and

minimum)

relal's,

and

quantity

sign relavs

such

as directional

and

polarized

relays.

distinitioo,

ir*'made

bet*ee_n

frotecttve,

;p*;;";;-;;;;Ioai],

;;;.;rp;;:

dence,

synchronizing,

etc.

relays.

F

(l-3u)

I

TMfRODUCfION

The

As

to

their

position

in

the

equipment

and tbe

functions

performed,

reiaS's

to the

circuit

whose

variations

make

the relay

funetion; secondary

rela-vs s'hen

the

detecting

element

is

connected

into

the

circuit

under

control

via

an induc-

tive

or capacitive

coupling

device; slave

relays

which serve

as

an

intermediate

eiement

in

ihe

equipmeni circuii,;

i,iming reiays

which

provitie

i.he

reguired

time

}ag in

the

device; indicating

relays

which

show the

condition of the

whoie

or

individual elements

of

the

actuating

device,

etc.

With

respect

to

the phenomena

used in

the

performance

of

relal's they

are

classified

as electromagnetic,

polarized,

semiconductor, electronic induction,

photoelectric,

ferromagnetic, etc.

Reia-vs are aJso

classified

q'ith

regard

to the pickup

and

reset time

(foand

t,.),

i.e.,

the time

eiapsed

from

the instant

the

acting

factor

reaches the point

at

u'hieh

the

detecting

element comes into action

(the

pickup

or

reset

magnitude)

to

the

instant

tbe

actuating

elenent

operates

or

resets.

Distinctions are

made

between

very

high-speed

(microsecond)

relays the

time

of which ma1.

be

con-

ventionall_v accepted

to

be

not over

one

period

(0.02

second). lrigh-speed

rela5's

rtith

tiie

time ranging

from 0.02 to

0.04

second,

instantaneous

acting rela-vs

ruhose

time

is

from

0.04

to

0.08

second,

and

slorv-acting

rela-vs whose

per-

formance

is

delayed b1' a

special

member

providing

a delay t.ime adjustment

or

rvhose response

time

depends on

the

magnitude

of

the parameter

to

rvhich

the

detecting

element

responds

(inverse-t,ime

relays).

I-5. Elements

of Logie Operations

Y

ES, A|OT

,

AND

and

O.R

operations.

The

y

ES function

is performed

by

the

operation

of an

actuating relay

(Fig.

I-Ga

and

b).

Nonoperation

of the

relal'

OR operation

is

obtained

by

parallel

counection

the

aotuatins

ele-

S

It

or

J,

etc.

is operated.

Cgmparison

operation'

The

effects

of

electrical

variabies

/

and

B

canbe

com-

pare{

Pechanicaliy

or

electricalll'.

The

mechanical

method

is

illustrated

in

Fig.

i-9.

when

gopparing

the

eJflctive

magnituaes

of

"rilr"rti";

currenr

rhe

operating

time

of

the

detection

element

musi

be

not

less

than

oorJeriod,

as

the

Fig'

I-7'

Performing

il"l^l:g:

operation

Fig.

I-8.

Performing

oR

logic

operation

b1,

b1'

conracr-r1'pe

relays

-D'

-

-' -'Jooii"i:tip,i

i"i-ji,

effective

vaiue

of

an alternatjng

current

is

asse.ssed

over

one

period.

\\rhen

comparing

the

magnitudes

of

direct

current

or rectified

aliernaiiig

cument

the

minimum

time

is

iimited

on}.v

by the physical

properties

of the

?elav.

/-\,ttc,

*-f*t*

E

tlJ

Tbe

ratiometer,principle

can

be.used to

compare

d.c.

magnitudes

(Fis.

I-10).

The

deflection

aqsle

o

of the

moving

coi]

instiunte"t

depeids

o"-in"

quotient

of the

currents

flowing

in the

loop

ioils

'(a)

Fig.

I-9.

Mechanical

comparison

of

(o)

witb

electromagnetic

system;

(b)

electrical

magnitudes

witb

induction

Eyst€m

(q)

Fig. I-6.

Performing

a)

I

@:

=-

E

YES

(a,

b)

and NOT

(c,

d) logic

operations by

eontact-

type

relays

(o)

when

contaet I{

closes;

(b)

when

contact

I{-opens;

(c).wben

contact

K makes

tbe cir-

cuit

ot relay

R;

(d)

e'hen

contact

fi

bypasses

the circuit

of relaT

A.E

is

charaeteristic

of

the

NOT

function. The

relay

may

be

of any

t1'pe

which ensu-

res

a

two-position,

stable and

positive action.

The ArOT

instruction

can

he

realized

by

the

schemes

shown

in

Fig. I-6c and

d.

The /ffD

one;ation

is

realized by elosins'

the

making contacts of the actua-

ting ;elays

in ieiies

(Fig.

I-7). Th; output" signal

is

f6rmed

only when

both

relays

lAR

(l/7)

and

zAR

(2II)

arc closed.

Comparison

may

be

accomplished

bv

a

polarized

relay

in u,hich

the

armaturl

of

current

flo.vving

in the

coils.

a trn'o-position

relay,

in

particular,

movement

depends

on the

direction

To

compare

guantities

|

/

|

and

lB I

a

null

indicator

may

be used,.

whea

the.quantities

1.4,1

aT.d

1B

1.are

equal.and

voltage

balance is

obtained,

no cur-

rent

flows

ihrough

rhe

indicaror-.

The

"urr"oi,

fi;;;

i"-;;r-lirec.ticu.

if

ld

t>

l.B

l,

and

oppositely

if

lA."l<

1r,

1..

rne

circuit

can

be

designerl

to

respond

to

a current

or

vortage

difference

(Fig.

r-tr;,,

b).

INTRODUCTION

INTRODUCIION

IDdugtion

devices

may serve as

comparisoD elemeDts

as

their

torqu€

is

dependent

nn the mrgritude end direction of the megnetic flures produced

bt

tbe

quantities

beiag

compared. Tbe same

principle

uuilerlies

the

operatioD

of

the so-called

alitferetrtial syncbros which have

two

operating opposing coils.

-Anotber

compariso!

method is the eleetrornagletic one.

The

us€ of dilferetrt

Fig. I-10.

The

use

of

ratiometer moving

Fig.

I-11.

Null indicator circuits

system

for

performing COMPARISON

logic

(o)

eurent batance;

(b)

voltage

balance

operation

windings on

a

common

magnetic

circuit core of

a

relay or

of a magnetic ampiifier

is

an

example.

In

this

case

the

effects

of magnetic fluxes

(Dl

and

(D2

produced

by

the

current

florving

in

the u'indings are

compared.

l-l I T-__l r*'*.

.,|, illi {

(t\

.f

(

\+/'

H_

L-_\l./ I

Fig.

I-12.

Circuits of differentiating

devices

AII the above-mentioned

principles

are

employed

in protective

relayiug

and

automatic

control systems. Their application

often depends

on

the

level

of

production technology,

patent policy

and

their

compatibility

with

other

pieces

of eguipment.

DiJterenti.ati.ng

elenzents.

The operation

of a

differentiating

device is

shown

in

Fig. I-12.

r.

g.

tri _

rI

RC"ff

K

Ur, then

(I-31)

(r-32)

(r-33)

,

The.outprrt

signai

taken

from a

differentiator

of

the

type

shown

in

Fig.

I-lZb

(a

passive

differentiator)

is

smail and usualiy

requirei

ancplification.

In

the

L

E]

^t

t(

>>

f00

I-13.

Variant

oi

a

diff

erentiatine

eiement

circuit

shown

in

Fig.

I-1,2c

and

d

the

current in

coupling

transformer

i:v

d.?

:k'{

'dtdt

Fig.

i-14.

Integrating

element

circuit

the

secondary winding

of the

(r-34)

l

/-

a)

The differentiating

eiement

may

be constructed

as

shou'n

in Fig.

I-13

with

an

amplifier

and

direct feedback.

A large

amplifier gain

factor

is essential.

As

comparqd t9 the

feedback

circuit

impedance

the

amplifier

input

impedance

is-very

high,_for

which

reason

the

current

branched to

the

amplifier

input

is

iairly

small.

For the

above-mentioned

reason the

potential

at

the.

node

b aitains

a

zero value

in

comparison to

the

potential

at

the

nodes a

(+U1)

and

c

(-Uz).

If

it

is

assumed

that

the potential

of the

node

b approximatei'zero,

then

tfre

ii

INTRODUCTION

transient

Process

may

be

written

as

follows

A

d.c.

or

a.c.

motor

may

also

be

used

by

the

integrating

element.

The

opera-

I}{TRODUCTION

i:

C

ol-'

:

2

T-_-T

(i-35)

(l.36)

hence

and

Since

and

then

or

fJz:

-

RC

+

Integrating

elcments-

The operating.principle.of

an

integtating.device

can be

understiod

trim

the

scheme

in Fig.

I-14

(a

passive integrator).

The expressions

Ior

the

circuit

are

1r

iR*

^ \

tdt:E

vJ

(I-37)

(r-38)

(r-3e)

/T-ZO\

(i-4{)

dLI,LiE

dt

-r

RC:ed

If the ruLio

UIRC

is

neslected

as

conpared

(I-42)

to the magnitude

of

EIRC,

then

(I43)

oence

u

I l' - ,.

:#\

Edt

$-44)

The

integrating

element

may employ

the

scheme

shonS

in Fig I-15.

Taking

into

accoooT

thrt"the

potentiai of

the

node

b is

negligibly

small

as

compared

to

the

(+Ut)

and

(

-Ur)

values

+

T,dt:D

RC#+u:E

Afi F

TNE

.

Ut

ndAz

,:-F:

-r-a

4l

uz:

-id

)

a,dt

(I-45)

(r-46)

whence

input

signal

caused

by

tbe

mismatch

between

the

actual value

of

the

controlled

variable

and

the

specified

magnitude

drives the

motor.

Depending

upon

the

m.ismatch

duration, the

motor moves the

slider

of

a

potentiometer

*[o*"

output

sigaai is

given

bl'

ibe

position

of

the

potentiometer

slider,

i.e.

by

the

totat

Fig.

I-15.

IDtegrating

element

Fig,

I-16. The

use,of

motor

in

integrating

elemeBt

(integral)

error

between the

actual

and

specified

magnitudes

of

the

controiied

variable.

The

control

system

emplof

ing'an

integr"iiog

element

"r

tru.

ti;;;

must

have feedback

between

the

contro"ller

outprit

"of

th.

input

signal.

IVulttplying

elcrnents.

Different

devices

*liog

rr.ol.*

tubes,

semicoidu"tor.,

Ii,ageetic.eiements,.

etq.-to

multiplv

a

variable

by a

constan.t

factoi

(amplifieri

having

-

a

constant gain

facto4

are

available

Depending

on the gain

fact,or

t,he

ouiput voitage

(Fig.

i-1ia)

a2:

kg[.t1

e_4-i)

rvhere ft"

is

ihe gain

factor.

To

k-eep

the

variables

under

con-

trol

and

the gain

factor

oonstant,

a

network

rn'ith

a direct feedback

effected

through

resistor

.Ro ma1'

be applied.

One

pole

of the

ampiifier

on

the

inpur

and

output

sides

is

earthed

and

ihe

voltage

of the

other

pole

is

indicated

with-

regard

to

the

earth

potential.

The

amplifier

is

so connected

that

the

input

and output

voltages

are

of.

op.posite poia-rity,

prus,

say,

at, the

input

and

minus

at the

output..To

simplify

1[e

grapLical

representation,

tnr

*"rining

contact

'of

the

other pole

is not

s[own.-

For

ad.6quate

operation

of the

equipment,

an

amplifi-er

having

a high

gain

factor (k',

raogiog

from

100 to

1000

and

more)

should

be used.

With

an adeguateh'

hich

pain

factor

(/r-

hpir,o f.sr^ mooror *}.o- znl-|\ +L^

nod.e

b has

a negiigibti

r{qtt

ioG"ti"i-G*i"ii*

tr"

**irj^;r";;##"j;';ii;

voltages

of nodes

a

an'd.

c. Ther-efore,

the

potential

diagra;

h;.

;h-irrm

shornn

(r)

Fig.

t-tz.

Muiriplying

element

ll

>2

lc

'l

r-

INTRODUCfION

INTRODUCTION

31

in Fig.

I-17

c with

a

minute

zero

drift.

since

the current

It:"fr:

then,

s'ith

adequate

accurac-v-we

assume

rt ff

UI

Uq

T;:

_E

rrz:

-R2(H+H+.".+#*)

shown

in

Fig.

I-17b

inverts

the siga

L-, /

-,1

\

rrJ

\

^1.

Connectiou

Diagrams

The

interaction of individual

elements

in

automatic

electric

power

devices

is

realized

first

by

representing

it

in

an

electrical circuit

diagram

and

then

by

analyzing

its fuuction.

Proper constmction

of a diagram,

its

clarit5'

of repre*

seniation, and easiness

of interpretation

b.v

tbe person

who

reads

ii are

not

secoudary design

tasks.

Operation.of any

device

in the

automatic

control system

without'a circuit

diagram

is irnpossible.

In compliance

with

the terminolog-v

of

the

unified

system

of

design

docu-

mentation

[I-1]

the

electrica] circuit diagrams are divided

into

block

diagrams,

functional diag.'ams, schematic diagtads, wiring

dldgrauls,

conn""tioo"

diat:

rams,

installation

dialrams

and

layout

diagrams.

The

bl,ock

diagram.,

c

rfines

the

essential

functionai

components

of tbe

device,

their

applications

and

intereiationships. It

shows the

overall

operation

sequence

of

its

separate

units emplo-ved witbout detailing the

internal

design

of

the

units.

The units

are designated b5' capitai

ietters

vhich

indicate the type

or applica-

tion.

Examples are

CU, Comparison

unit, SU Supp}5'

Unit:

YES,

NOT, OR,

Al{D }ogic

operation

units;

TU, Time

Delay Unit; h{U

lt{easurement

Unit;

DFBU

Direct Feedback

Unit; AU Ampiifier

Unit; etc.

TIu

functional

d.iagram

explaias certain

processes

*'hich

take place

in

indi-

vidual

circuits of

the

device

(eguipment)

or in the

device

as a

r,'hole.

Denicted

in

the

functional

diagram

are

the

functional

co:rponents cf the

rievice

(elements,

units

and functional

groups)

which

are

invoived

in ihe

process

illustrated b-r'

the

diagram

and the

relationships

between

these

components.

Aetuai

couplings

between

the

elements and

u-uits may

be

sbown

in

these

diagpams.

Thc

sclwmati.c

diagrarn

identifies all

tbe

components,

shos's their

relation-

ships and,

as

a

rule,

gives

a detaiied

idea of

the

operating principles

of

the

eguipment.

The

schematic diagrams ma-v

be

either combined

or rleveloped.

Conventional

symbols

are

used

to

shos'

the

detecting

and

actuating

compo-

nents

on

the e,ombined

schematic

diagrams

of

the

electriaal controJ

device.

tTtL^-^

+- L^*,^ +L^;-

^^+,.^'l l^^-+.i

^*^-:+:^l ^-. +L^ .]:-

T-

I

IIIJDE-

tJUIIIP\J.llrtu

!r Ili1

Y

E

LIlEirI

<lUL(rdl I'UtJll \,lti-ll a1J JlrtrLIIltit-l

Ull

L,Ul,

ltt aHI afU

,

llI

three-phase

equipment,

the

device-"

are shourn

connected to instrument trans-

formers, whiie

the

latter are drawn s'ired to the

phase

conductors

of

the

pri-

mary

circuit

as

in

actual

service.

A

schematic diagram so

construeted is

combiaed-

rx-ith the connection

diagram,

i.e., with a

diagram

u'hich

shou's the external

connections

of

the equipment

The

combined schematic

diagrams mu-st

illustrate complet.ell' the

interre-

lationships

of

t.he

elements

in

the device

as

v'eII

as

that

among

the

devices.

AII

apparatus

used must be shown on

such

diagrams.

IVajor

units

including a series

of devices

and

relays,

are

depicted

either as

a

single

apparatus

or a*c

several

eiectricaliy

connected

devices

enclosed b,v a dotted

line

indicating a complex

design.

If

a

major

unit

is shown as aD

apparatus

without

iliustrating

its

internal

wiring,

a

clarifying

drau'ing

must

be

given.

The developed sehematic

dia-gtanos

whieh

are

somet.imes

c.alled

olgynsnt,

diagrams

show

eJectrical

circuits

from

beginning to

end,

for

example, from

the

positive

terminal

post

of a storage battery

to

its negative

terninal post

or from

t

(r-4e)

and

Under

these

conditions

of

the

gain

factor

k, of

the

Fis'.

l-1E.

MultiPIYing

-

element

circuit

hence

Inverters.

The

network

arr-- : - ---l+:-l'i^-

guanLlbyt

I.g.

r

l.lluturPrrED

-

\Vhen Rr

:

frz

fig.

t-ig.

Summing

network

uz:

-ftu,

(I-50)

the

output

lroltug,

fri,

i.

practically

indep-endent

amplifiei.

Thus,

the

device

automaticaliymultiplies

IJ,t

R,,

>r

RrlRl

q'hose

value

is

controlled

bI'

ie

multiptying

mesh

has

the

form -shown

r- l-^^- +L^ *^-a.inol l^orl

lrn'l*ooo

nnn-

tu

K

titi

u

Llllt

Lvt

uf uqr

rvq

u

fir

:'-Rr,

thea

Uz:

-Ur,

regardless

veral

quantities

car

be

zummed

mecha-

,ily.

Tieated

belou'

is

one

of

the

possibie

tions

electrically

with

a simple

mesh

rn

in

Fig. I-{9.

In

compliance

v'ith

for-

We

may

u'rite

r,:H+#+.

.+*:-#

(r-5{)

(r-52)

of

the

input

k

>t00

Uz:

-fir

INTRODUGAION

AJ

oz

INTRODUCTION

of

an

instrument

transformer

to its

other

terminal. The

one

r

horizontal

and/or

vertical

lines.

As

compared

to

eiectricai

the

com-

bined

schematic

diagrams

the developed

schematics

make rt easrer

to

c

I"r""..tn".s of electiical

counections-

and

absence

of

by-pass

faults.

Separate

I-7.

Conelusions

2.

Automatic power

control

-cystems

make

electrical

operations

of power

relaying

devices,

radicaliy

improve mai-ntenance

and

also

and become more

and more

bution

of

electrical

power

of

power

systems.

3.

Automatic power

controi systems

are

buiit

up

of

various

types

of

trans-

ducers, controllers

and

relal's operating

in conjuncti.on

rrith

intermediate

autonaatic elements

such

as amplifiers, rectifiers,

stabilizers,

time-delay

devices,

differentiating

and

integrating elements,

memor)'

systems,

etc. The perfor-

mance

of

automatic

power

control

systems

obel's the general

las's

inheient

in

various

control devices or in devices

performing

reiaying

operations.

4.

The

practical

use of

an automatic

pov'er

control

system

should

be

effec-

tive, i.e.,

must

be advantageou-s and

economicaii-r

sound

as

well

as

guickly

rePafing

its

cost.

-

5.

At-equal

costs

of

using'remote

or automatic

control

of

some

process,

pre-

ference

should

be

giVen to the

use

of

automatic

control

s]'stems

as this

reod"ts

controls

such as regulators

is

clear-cut.

With

discrete

operating

automatic

controls,

distinctions

are

made

betrveen the

modes

of

operation such-

as

"u,aiting

time"

and

"aiarm".

It

is important

in

the

practieal

use

of devices included

in the

family

of au'uomatic

control s1'stems that tire

elements

employed

are

dependable,

+L^,i^^:-.;^^^^^--l:^L^J---^.l.laL^^^-^_L.|-.

ur.r.r,

uvDr6rr

rD

aL;L'ur-uPlrDuvu

wtrrr,

t,rlt,

asSgrIrIJr_\

oijeratluns

arg

pgrlorllgo

L0

nlgh

standards

and

the

system u'orks

*'eI}

at

ali times.

7.

The

graphical

representation

of

the

diagrams

of the

automatic

conirols

should clearlv indicate

the interrelationships

between

the units

and

be

easiiv

interpreted

to

facilitate

installation

and

operation.

I-8.

Review

Questions

t.

What

automatic

devices are included

in the

assemblage

conventionally

called

.,auto-

matic

power

control

systems"?

2- What is the relationship

between.operation

of individual

elements

of

the

automatic

power

co?trol system

and

protective

reiaying?

3' What

are

the. requirements

for diagrhmi

depicting

devices

of

auLomatic

power

control

ot?t',+tgr*9-Tf;3:$#t''iJtTglreiaying

devieos?

irTame

r,he

disiinctive

iearures

encounrsred

in

the

3-2076

terminal

generation

and

distri-

performance

eleme:rts

operation

of transducers,

relayJ

and controilers

(regulators).

What

are the

pickup

and reset

vaiues

of a relay?

Ddfine

the

reset-pickup

ratio.

u

INTRODUCTION

6.

rela'

3

-

8.

What ar€

the

speeific

leatures

of

the

control by the absoiute

a controlled

variable

from

tbe specified

value and

by

the absolute

controi by

i,he

rate of deviatioa

added?

of

an amplifier in a

control

system? Describe tbe

performarice

of

and

elastic

value of the

departure

of

value

deviatiou

with the

What is

the

used

as

an

'

7.

ll'hat is

tbe

DurDose

()1

leed.back

rD automaf,lc co

negative

feedbacks.'De-seribe

the direct

.(continuous)

a

]sl,

uescrrDe

posltrlc

and

(sample-data)

feedbacks.

AUTO]VIATIC

CO]\

TROL

OF

SYNCHRONOUS

GENERATOR

EXCITATION

9.

l\tat are

control

elements? Describe integrating and

differentiatiug

elements.

10.

What are the

}ogic operations used

in the operation

of automatic devices?

11. Erplain

the terms

"astatic

and

static

cbaracteristics"

of control

processes.

Deiine

the term

"itatic

coefiicient".

12.

What are

the static aud dynamic

cbaracteristics

of

the

elenents of

a

controi

system?

What

is

static

error?

Describe tbe methods

for its

decreasing.

13. What

are

the features

of aperiodic and oscillating controi

processes?

14. Expiai-n

the difference

between

the remote control

aud automatic control

of certain

processe-s

carried

out iD

power

slstemq.. Name

the

advantages of the automatic

control.

-

15.

What

is

tbe overall effect on

national

economy

of the

use

of automatic

power

control

svstems? How

can

this

effect be

determined?

'

16.

Explain

reliability of automatic

power

cortrol

systems as one of the

principie

require-

ments

lor t[eir devices.

\\Ihat are the

methods

used for

guantitative

estimation of

the

reliab-

ility?

1?.

Describe

the

electrical connection

diagrams

oi automatic

power

control

s1'stems.

Erplain

the types

and

purposes

of e)ectrical connection diagrams.

f

-1.

Purpose

of

Automatic

Excitation

Control

(.A.EC)

Deviees

he1.

respond

and

on the

type

o!:eslronse.

t porver

system

ma]:

be

ejtlier

probortii_

iormer

group

jncludes

automatjc

excita_

rolaritl'

and value

of variations

in

the

excitation

forcing

device.

In

the

presenCe

of a quick-opera.ting

excitation

system

the

overaction

cont-

rollers

assure guick

contfol

and

mainta-in

the ooit"g.

across

the

staror

u.inding

Q*

U

i

and from

trianele

O-^'.t

i.erninats o! across

the outpu'u

terminals

of

a

stop-up

tlansformer

(when

the

I

-

^r-'ll: Easild

a.snerato!

operates

iointriii

i

*"o

ssnerato!

opefares

Jorlruv

rdrlr

c.!r4u:.t?tiJJriJ"

il"-trciLtion

forcing

device

i

tbe!

1ffi,*:Ttl;*|""lli."tui;:,"il1f;;;ifi;i;;;;[-ty

erement

an-d speeds

I

Edsi!0:1r2',2€oss

CEAPTER

OI{E

if,-thi

controi

process.

^-^..+-+ia; ,^r.ind !n.t .^nrrnt 1

taking

into accorrnt

(1-12),

rve obtain

H";;t";;"d';;;iluslv,

the. wide

use

o1

excitatiotr-Io-rcrns.:11^::^"'fl

I

ii'iir"'"iia"y

lul;

prdbte-

in detail.

I

corresponds

to the lalne oJ

sin

6:1,

i.e.

ll

9!"

,/

(a)

(b)

Fig.

1-1.

Operation

of

s5rnchronous

generator

in

po\r/er system

(o)

equivalent

circuit;

(b)

vector diagram

rr,,r:l+#l:l#l

(1-1)

P:Ulncose

$-2)

1-1b

that

in

triangle

MSAI

angle

I{SN:

q

and side

and

It

is seen

irom

Fig.

.SJf

:

,SM

cos

P.

Since

from

({-1)

SM:

Innn

JI

I

..1,UTOll-tTIC COI.'r'TROL

OF SYNCHRONOUS

GENERATOR

EXGIfATION

--

r-.._-_:.-

ior-

i.pr6"iog

-p"rar]it

operation'stability.

i -f*^:ltlilf^ :]:,t.1r.r,^".d:,_"f

aclire.p^oler

(P-)

nhiclt ca! be

transnitted

u""ff",'t-X"J#"1"nJ:J'HT'''rT"il'";'-:l"i;"ib;;-;"h::u''

$,y:^"-".":l: I

-

P-1Eo"iod

(1-3)

*iiil1}'voipo*.ersyst,ems.TbeuseoIAEedevicesisofspecialimportaace

i"'tll

"ta,

Iet

a

iynchronous

genetator

o-perate

in

parallei

-with*

a

hjgh-

I

power

syste'

through

a

po*u,

,""oEio-"-"'-aud'

a transmissio"

ri"t'ii'ig'

l-'ri'

I

e^:

!!!-l

(4)

and

E

-J^

.i

I

P

:

P.. siu 6

({-5)

;r , ,/-)<\ I

J

ffi-JiEx!ressjon.(l-3)does'nottaLeintoaccountthepresenceofaresistancecom.

tt : -_ -_.

ponent

(rr=)

of

tire

imlleclance.

Sucir an assumption mav

be

made

for

a

qualita-

tive

ana]-vsis

of

parailel

oper.ation -stabilit]=.

(oJ

,,c

/

Fig. 1-2.

Effect

oI AEC

operalicrr

on

increare

in slatic

stabilitl'

(o)

changes

in terminal

voltage of

generator

when

-E6

is

constant

and

ang)e

6

jncreases;

(b)

changes

in

emf

of

generator

when

generator

terminel

vo,tEge

is

maintained oonstant

and angle

6

increases;

(c)

characteristic

of

changes

in

power

when

U,

is

corutant

How

tire

operatjon

of

AEC derices increases

the

stead-v-slate

(static)

stabi-

lity

can he seen

from

Fig.

1-2. \A:Iren no aut.onatic

excitation cont.roller

is

used

t,he

genorat,or

emf

i-c determined

by

the

invariable

value of field

current

and

c

Ldl

v.!,'

rins!

;

0 20

t0

CA

Et

!!i

t?i

l+[:

t6tJ

tt1

CHAPTER

ONE

remains coDstant

uDder

lault

conditions

(td

:

const)

The

voltage

scross

the

,

The eicitaiiotr

cunent ri6es

causiug en

iDcrsase iD the

generator

emf.

whea

qigla=:9lLep._ip.sE

Eils_Yto:ulJlj:ld:g::3j_.s:_c:iT._t:z:d_

T:o_I:r::

'

lqrcins..d;;;;; !,b€

iiel; coil or rh;-.'h;r"

p*;;;;it"e","tq,

n" whleb

'ri:i:'#lTj

*o'iu""J.""':"f'f:

lllf'"f':?$';T:t'i"J:i#lii:1f

rea:ra'ce

|;?hl\""Ji;""-l"ti;;,\1"?,"","f""*11t#t"*trf"""'f

k":U,*'.:g:;

As the

load

angle 6 iocreases'

i'e', with an inqease in the

pov'er

being trans-

exciters enplotd

; fo*-iid

io"r*"r" in the

elcitatioD

current

ro

eDsure

extra

mitted,

tiie

emf

vector on

the diagram

takes

the posiii

o\

b|,t

arld the

vector

stabiiity.

\rr

lue

yvrvqsv qvrves

"

i

(Table

i_l;t

r

.t3.

tnen

lus-u

I

10"-ot

As

seen

from

Fig. l-2a,

I

ULI is less in value than

I

U,l,

i.e.

la

sl-ii';:

nu

$-7)

If

the detecting

eiemant

(primary

detector) of

the

AEC

device

responds

to tbe

vaiue of

AU

and

tends to

maintain

Atl

:

0 bl'changing

the

fieid cument

of

the

generator,

it

u'ill

be seen from

Fig. 1-2b, that

the

generator emf ex-

ceeds

tbe

E6

t'alue.

When

maintaining

t''g: constant,

the

ordinates

of

the

transniLt,r'-d

Fcwer

charaCteristics

exceed the

ordinates

of

the

curve

plot,ted

on

the basis

of

(1-3)

for the

condition

*'hen

E6

is

constant,

operation

of

the

generat'or

becomes

fea-

sibie

rvithin

t,he

artificial

stability

r<,-i^- i o --hon

A

--

QOo

/E'i-

4-9^\

r9SrVIrt I.w.

t

n lrvu v

/-

vv

\r

^5.

To stqnai

9-+

1-2.

Automatic Excitatian

Foreins

of

a Generator

The

operating

principle

of

the

quick-acting

generator

excitation forc-

ing circuit

is clear

from

the diagram

.

shown

in

Fig.

1-3

which

illustrates an

.

electric machine

excitation system fur-

-

nished

u'ith

an automatic

field

discharg-

ing controi

using

discharge

resistor

R6

Fig.

t-3.

OFerating

principle.

of

.a

device

to

absorb

the

power

accumulated

in

-

for

automatic

excitation forcing

the rotor

winding-

\Vhen voltage

across

the

termirrals

of

the stator

winding

(or

at

the

specified

point

of.the

cirouit)

drops

to

thc reset setting

of

voltage

relay

I/.R,

theiatter

cioses

the contacts

and

shorLs

by

means

of

intermediate contactor

l(

resistance Rl

placed

into

the field

coil circuit

of

the

exciter.

oI

the

voltage across

the

gpDerato!

termitrals is detelmiDed bv the

vector

L!,

I

,.^5jt\forced-veDtilated

machines'

foreing is

permitt€d

oqly

for short periods

AUTO}TATIC

CONT:TNOL

OF

SYNCERONOUS

GENERATOR

EXqITATION

Table

1-1

I

Ea-U

o1 |

E|-AL

I

/,r a\

Permitted

ExcitatioD Forcinq

Duration lor

Forced-VeBtilated

\1-u,

Turbogeneralors

It-5i

Forcing

factor

Turbogenerator type

TVF

(TBO)

TvV (TBB)'

and TT\I(TTB)

With

self-cooled

machines.

attending

personnel

must

eliminate

the

cause

of

operatioU..of the

excitation

.forcipg

device-q

not

iater

t.han

one

minute

after

tire

device has funct,ioned.

Pror,ectioilof

the rotor

againsi

overloads

and

limita-

tion

of

rotor

overload duration

b1'

deexcitation

are-specified

in

the

seryice

cir-

cularI

t

-21.

Shown

in Fig. t-3

is a

circuit which provides

for

instantaneous

reset

of the

forcing

device

after the voltage

across the

terminals

of

the

l/ft

relay

has restored

its value

at

which

the

rela5'_contacts

open.

Circuits

of this t,vpe

are'*'idely

used.

in

order to maintail

stabiiity

in after-fauit

operation,

it is

good

praciice

t,o

continue the excitation

forcing

action

for

a

specified

period

aftel

the

iault

cause

ltoo ,lioo-^o--arl T- +l"i- ^^-^ +1-^ ^+^L:1.34--- J.:-r---L r

.

.1

aqa urpqPPvqreu.

ru

urr'l'D

ud,Dltr r,uE

DLaITIIILy

UfSLt.l[-!AUO€S

€IICOUnLgIgq

In lne

second

hunting

cycle

can be

prevented

in

a number

of instances

due to

the

inc,rea-

sed

emf value

used

in

the

after-fault

conditions.

ON

position.

CEAP{ER ONE

fron

outpul relay

Fig.

1-4.

Actuation

of

excitation

t:;""t:"tr*"tir?Jtth

reset

delav

and Umited

relays

open

the making

contacts

is

seJected

as dictated

!y

tfr.

-adjusfment

con-

ditions

of

tne

excitation

forcing

device

so

that

it is

not

affected

by

the

operating

voltage

f/1 scross

the

generat,or terminais,

th.e

margin

(factor

of

safety) k*-bellg

equal"to

1:05.

When

the

reset-pickup

ratio

(tr.)

of

the

voltage relat'eguals 0.9,

tir'e

contacts

will clo*"e

at

the

voltage

across

the relal'

(U,rroy)

equal to the

reset

AUTOM.ATIC

COIqTROL

OF

S:TCENONOI]S

GENERATOR

EXCITATION

The higher

the

k,

of.

the

voltage

relay,

the

more

effeotive

is

the performance

of

the exeitation forcing

deviee.

The circuits of

the excitation

forcing

devices

shown

in Figs.

1-3

an d 1,4

ensure

the fcrcing

operation

in

case

of

three-phase

short-circuits

end when

faults

\

t2\t4

ts

t6

.'

O'rU. 1-5.

Changes

in

voltage

wben a

short

circirit

occurs

anC after

it is

cleared

1r

-_the

instant

a

short circuit

occurs;

.t,

-

the instant

tbe

excitation

forcing

device

functions;

ts

-

the instant the

sbort cjrcuit is

cleared;

t+

-

tbe linstant

tire

cirduit voj-

tage is

reestablished

to the ralue

at

which

relaTs

JT'R

and zl'E

(Fig.

1-4) open

contacts;

(16

to 14)

-

tirne

for

rejay

D.R to

reset:

te

-

time tor

voltage

to

iestore

to

the

nomina-i

value

occur

between two phases

to

which

the voitage

relays are

connect,ed.

\\zhen

faults

occur

between

the

otber

two pirases

and

in the

case

of an

earth

fauit

in the

a

power

transformer

it is

good

practice

to

connect

the

voltagereiav

of

tbe exci-

tation

forcing device

on

the

HT

(secondary)

side

of

the

power

transformer

or

to

the

generator

voltage

which

is

cunent-compensated

to

the

value

of

the

secon-

dary voltage

of the

power

transformer.

4t

The

opersiioD

ol

the automatic

exciiatioa lorcing device iD coDjunctio!

voltage

U,

with

the actiotr oI

the

geperator

excitatiop sFtem

determines tbe rsgulstio!

-

-.

cbaracteristic

sho

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

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