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

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Prodihilion

ol

turni

ul

,r/zcn

ngt

rgady

fo

startrno

tiostn.q

{ime

reiov

for

contrc

i-a;

slarl.

a:iral

t en

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woter

altd

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e,l t r

n,o

h

ydra

u

/ t

c

o

c !

d. o

lcr

ot

ltmrter.lo

nc.lud

pcsthon

Ceneratton

unil

gatns

sPeea

Clostno

ol

geyerator

st{r Ic]?

Autotna

tic

synrh

rani

zc it on

fDC deyzce

qi

ves

ex ci

la

t

ion

Startino

relau

tr'i.pping'

Opening

"!

nloy

coalrollug

start

duration

Setltng

turbtne

roiolzno

,'lade

ta

qeraitno

posriT"on

Apera

I t en

ol fre,y

u

ency

-

dilfe,

or

speed

re{au

lUFR

Fig.

6-9.

Suggested

sequeDse

of

operations

in automatic

tric gpneration

unit

starting

of

hydroelec

oi

fre

Fig.

6-8.

Automatic

h-ydtoelectric

generators

when

power

system

CIIAPTER

SIX

.A'UTOMATIC

CONTROL

OT

FREQUENCY,

REAL

POWER,

PO'WER

FLO.fri

205

6-m

head

and

load

of

the u'orking gene-

rators

so that

the

most economical

n'orking

of

the

entire

pc wer

station

is

achieved

(rwith

due considerations

to

the

method of equal relative

increments

and

]osses

in

the

trans-

mission

lines)

and

that

the specified

amount

of

spinning

reserve

is

en-

sured.

2. When

the power

s,vstem

fre-

quency

falis

below

the

rated

value

automatic actions

must be effected

to start the

stand-b1'

genelators

anrl

tc

change

over

tire generators

ope-

ratrng

as

s]'nchronous

capacrtors

to the generation

dutl'.

3. The

first

generator

of

the

stand-b_v units in

the

sequence shall

be

started

s.hen

one or

more

of

tire

*r^-l-in+ annnrnt 'li--^**^^+^J

wur

ArrlE

Bsusr

d

r.ur

J

dltr

u

r-uul-ttlru

uvu

due to

a

fault,

or

rvhen

a h;,-dro-

generator

is

disconnected

frc'rn

the

.

:group

automatic

legulai,ion

s-vslem

for

some

other

reason

than t,he

auto-

matic

operator's action.

4. When

the power

syst.em fre-

quency

drops,

the group

control

device

(the

load

controller)

shal]

be

automaticall5'

acted upon

so

tliat

ail

the

generating

units

controlied

by

this

device take

a maximum

re-

sistive

load

even

if

it

exceeds

the

vaiue

preassigned

by

tlie

Joad sch*

dule.

Diagrams

explaining

the

princip-

les

underl5'ing

the group power

re-

gulation

of

the

power

station

units

are

given

in Fig.

6-10.

Control

soleuoids

J and

2

of.

tbe

irydroelectric correctors

of

the

hyd-

roelectric

turbine primary

speed

governors

are

connected

so

that

If the

current

flow

in

cotl 2

is greater

than

that

in

coil

-/,

the

oil

svstem

of

the

corrector

actuates

the

booster'ie;"r-"i-ll;

p.i*"rv

speed go.',n#o#;;=fr.;;

the

gate

ap.paratus-

The

reverse

_ta\es

place,

ihro

the

current

flon, in

coil

,I

is greater

than

the

flow

in

coil 2.

The

degree

to

which

it;- g"-t"-

apparatus

is

opened

is

controlled

by

synchros

operatidf

as

transforaers.

it

"o

lTt

r".ii"f

current

voltage

is

applied

to

the

rotor

coi"I

of

such

a

*v"rnro,

iiie

emf

at

the

output

of

the

stator

coii

r*'iil

change

*,hen

the

rotor

turns.

The

use

of synchros

makes

it

iossibl.

to

instail

;h";;rlizing

-circuit

ar

the

central

control

station

and

uiiliz.

.."i1

l""gr

connecrrgg

cables.

,

In

the

circuit

shown

in

Ffg,

6-10a.eachi,""q]r?"

1is

connected"into

the

equal-

izing

circuit

througF

a

-contro]

switch

CS

oi

the

machine

invoh,ed

in the

auto-

mqtlc-groqp^control.

Under

normal

operating

conditionr

tnu

torques

of

soie-

noids

'Z

and

2

are

balanced.

If one

of

thl

machines

rr"..rr*"grd

iii-toaa,

the spa-

tial

position

of

the

synchro

rotor

u'iil

chandil

an additional

e,nJ wiIJ

"onear

across

the

stator

outnut.

'-'

-rr'--

* l:]ntlo.

t:o,the

vbitage

vector

feeding

the

equalizing

device, the

add.itional

emf

s'ill

be

of

dtfj.r,e,1r_,

phase

shift,,

depending

oo

the

p&itioo

of

til"

gate

appa-

rztus.

As

a result.

the

current

u'ill

riie

in

c"oi}

Z

of lhe

g;;;;

eorrector

of

the generator

which

n'as

the

firs'u

to

take'the

incrementa"l

]oad.

Accordingly,

the

current

in coil

I *'ill

decrease

and

the

jala

apparatus

will

start

to

slos,Iy

close.

As this

happens.

the

current

flow

*"'oifr

Z

of

the

correct,ors

of

the

speed

irs

wili

dec.rease,

while

thai

il

coiis

r-

will

start

to

open

gradually.

rrs (total

]oad

of

the station,

power

flows

re

regulating

process.

To

thij

end

use

is

)rmer

C7,

the

secondarv

emf

of

v,hich

:ctance

coiis

-RC1

and

RCr.

:nor

correctors

empioying

solenoids

.i

6-10b),

the

output

voitagE

of

syncirro

J

governor

hydroeleetric

corrector

of

each

regulation

are

connected

to

the

equalizi

In

order

to

avojd

readjusting

tle

gro

machines

is. tripped,

ballast

resistot

6"is

cut

in

by

auxiliar5,

rela1,_c,4p,

the

contact

position

of

which

depicts

the

cperating

state

of

the

machine.

\

rd

\

s

P

\

o

6-6.

Frequency

and

Power

contror

in

Integrated

power

Systerns

Fig. 6-10.

Grou regulation

hydm-

speed

noid

stem

i.e.,

coils

are

balanced.

of

the

corrector is

the

oil flow

oorts

the

oil

sv-

turned

off,

are

closed.

(c)

suppl-r

to

(t)

dc supply

to

CEA.PTER

SD(

AUTOMATIC

CONTROL

OF FnEQUENCY,

REAI,

po.w:En.

poWER

ELOW

available

and the

condition

of equipment

(in

particular, the

maintenance

it

ueeds)

weather

conditions

(Iightning

storms,

high

winds,

.ice

and sleet

storms,

Pover

svsf,ems

ot

Ifest6rn

Siherio

,{-

Anzhers*aya

suistali

iaishet

substation

llrasnoyorsf

pover

system

Ir*uts*

poyer

system

.

An

integral

par!

q{

the

s5'51g6

regu}ation

scheme

in

a

large power

engineer-

ing

centre

is.

a

periodicalil'

operating

flow

regul.ation

s_vstem, .in""

tropi"tro.a

charlges in

the load

may first

of alf

affect

tf,e

intersyit.*

and systerit iinks.

in

-the

compiex

power

engineering

centers.

the

fiow

iesulation

naust

be con-

^lotdr+>ap",-o

ls

t

s

F3.

o,.$ i

.s;

x

Fig. 6-11.

AFP&FC

in

Siberian integrated

system

llta^Iu.luM1llu

lLlIIIrILltll'u

uguPsrquusor

vuv.

rvr

q^^

srvq,//'t

-sv

v-rr

water

and

fuel,

determining

{heir

consumption

rate

(i.e.:

decrease

in

tion output

fron

powel

stations operating

on

coal,

gas,

oil);

ens.uring

a

(6-7)

b-v

means

of

a frequenc\r

regulator,

.

2-

Regulation

gt

t_!. inters;r'stem

real power

flov'

over

the

500

kW trans-

mission line

from

t'he

Nazarovsli

power

station

to the

Novo-Anzherskaya

substa-

tion

by

t.he

criterion

lt

to

with

tbe

aid

of

a

power

flow

regulator.

genera-

certain

power

output

by- different

powef

stations

(for

example,

heating

ancl

CEAPTER

SE

3.

Combined

regulation of

the

freguency

and

intersystem

power

flou'

over

the

transmission

iine

from

the Nazarovsk

po'wer

station

to

the

Novo-Anzbers-

kaya substation

with

simultaneous

operation

of

the

frequency regulator and

the power

flow regulator

b-v

the

critenon

l.

l1

(6-e)

4.

Frequenc-v

regulation

vdth

a

specified

allocation

of unscheduled

power

among

the

receiving

and

sending

parts

of

the

pow-er

system

by

the

criterion

AUTOMATIC

CONTnOL

OF FREQUENCY.

REAI

PO'WER,

POWER FLO.W-

integrated

power

systems

the

with periphery

power

systems

P

by the

intermediate

substations

"

J

ol

dt+KK"j or,

dt+ZaP"i:o

16

lo

l1

x

I

u

dt

+

KK,Ku.^r"nLP

]t+

:

AP,,- 0

J

(6-10)

is

accompiished

by

ihe

simuitaneous operaiion

oi

ihe

freguency

and

power

flow

regulators.

Poq'er fiow

is limited by

limiters

lPFL and

ZPFL which

function

n'hen

the

actual

power

flows

(P.)

over

the lines

under

supervision

exceed

the

rated

power

flows

(Po)

over

the lines

ttnder

supervision

exceed

the

rated

values

corresponding

to

the settings

(Pr.

r),

i.e.,

\r'hen

Po>.

Pr.

t-

\Vben

an

outpuf

signal is

available,

the

por*'er

flo..r'

Iimiter

operates

a regulator by

the

criterion

.l

K

I

nn,,,o,dt*

)

AP",:o

J

"'-'

L

l9

(6-11)

performing

transient regulation

of

the critical

specified

pou'er

flow over

the

transmission

line,

i.e.,

wJren

Po

--

Pr.t.

When

the

causes

of

the line

overload

disappear,

the }imiters reset

and

the

power

stations

invoh'ed

in the reguiation

automaticalll'

1g1*tn

to the

power

determining

the allocation of

unscheduled

power

among

the

power

stations

Fig.

6-12.

Examples

of combining

individual

power

systems

into

integrated

p5wer

system

(q)

bV radiai

peripheral

tie lines

(FC

-

correction

oI

cnttcal

power.fjoB-

X.F

by section

flo\il):

(b)

with

tie

.lrnes_

througb

intermedjate

power

s1'steme

(in

ile

lrne

!bPz

real

powerflows

may be either

from

t.z

to

{,1 -9r

vice

versa):

(c)

bl

ring

tie

links

(r

-

unloaorng

internal

tie linss

being overloaded)

of

these

tie

lines

has

no

percentible

effect

on

the

critical permissible

value

of

real

_power

flows

(Fig.

6-i2a).'

Unscheduled

changes

in'the

load.s

make

the

frequencv

depart

from

the

rated

value.

The

orimarv snccd .,n'aFyrnFc ^r ^II *^*5:i:r- :'-^:-"I-:- r -

faults aud isolation of

some

parts

of

the 500-kV

trausmission

lines,

protection

and

interlocking systems

which send alarm

signals

to

station

personnel are

correctors

of

the

quency

regulator

Under the

actioa

t4-2A76

group

control

devices

of

o!

t_he

integrated

power

of

these

devices

t[e

load

power

stations

and

tbe

central

fre-

system

respond

to

these

departures.

is to

some

degree

redistributed

and

fr-l

Hore

u

to c.PJ

and

P4

provided.

210

CHAPTEP SIX

AUTOI\IATIC

CONTRoL

oF FREQUENCT,

REAL

POWER,

POW.EP.

FLOW

2tL

in

order

to

reduce

the

pov'er

flov's

betwe

pheral

systems

are periormed

on

the

ord

personnel

on

their

own

from

instrumen.

loads,

the

intermediate

tie

lines

shouid

check

the

total

amounts

of iacoming

a

unload

the

intermediate

power

s1'stem

st.ations

v,hen

the tie

line

over

v,hich

p-o$-er

flows

to

the

central

system

is

overloaded,

or

ioads

ihese

stations

'*,hen

the tie

line with

incoming

ieal

pon'er

is

overloaded s,hile

the

tie line with

out.going

real

power

is underioad.

.

4

iimiting

!]iste=.utilizing

the

above-described

principle

is

operating

it lht,power -grid

of

the

European

part

of

the

USSR-on

the

Centre*Lenin

\;olga

hydraulic

pov'er

station-Ur"i

tie

line.

After.

accontplishing

the

local

limiting

power

florx, s-vstems

on

tbe

inter-

svstem

tie

lines,

the fregr:ene.r]

tegt.rletion

i.i._'ho

nl.rod

-,.:ifh

tho u.onrrol ?4r.!!!:

]itor without,

the

rist: ;i;;.;";;;-;;;;"

"ir.[]l'=1"-I-"ji:r.-1.i;":i:i'j.=::

var

ia ti

on s

o..u.

i

;f

;.

";;

{ii.'l,s"

ri rl'

""'1i

ii

J'

;;;

ffi#J']"';"Jit?

Ji

ff

;

r9r.ul1!in{

Power

stations (direcily

or

through

the

centralized control devices

of

individual

systems

contained

ln the

int"egrated

-"ystem), o'hiir

the

other

power

plants

continue

to

foilow

the

assigned

s?heduie.

The task

of the,ioad-dispatching

pers*onnel

engaged.

in

operating

the

s1'stem

is

to

ensure

a needed

reai-po*er

s-pinning

reservE

it tU"

t"g"tntio"g

lpiloi)

pc,-

wer

siation

and

that

tbe

fior"

o{

thrr:t

power

over the

transiissio"'tines

li noi

blocketi.

.

(c)

The

integrated

-system

is

obtained^b5

ring

connecting

ind,ividual

regio-

111

poyer

systems.

The

central

AFP

&

FC

regulitor

is

insralled

ar the

]oad-

dispatching

department

of the

integral

can

control

the

regulating

power

static

rectl-r'

or through

the

AFP

&

FC

devicer

partments).

The

ioad

share

is

set

bv

thr

operating

conditions

of the

inteerited

The

assignments

worked

out-bv

the

and

liruited

to

the

reai-pos'er

flow

values

of

the

intersystem

tie

lines.

The

totai

incorrling

and.

total-outgoing.

real-

porner

is considerecl

(balancing

of

the

P.o\r:9r -fiow)

as well

as the

ciit'icil

real'power

flows

permissible

over

certain

tie

link

sections.

the

powcr

station

generators intended

to irandle

the

unschedulcd

variat.ions

of

thc

load

are

su'it,cired in b1'

tire

central

frequencl:- regulator

having

the Ieast

steadl'-state

stabilit--v, t.he

Ioad

sharing being as

preassigned.

An

increase

in

t.he

generation

of

the

outiying

po\\rer

systems caused

b1' tiie

action

of thc frequencl'

reguiat,or may result,

in a

dangerous

overioad

on

certain

tie

lines. Overloading ma),

also occur

if the centra]

power

svstem

undelgoes

a

lack

of

power

due

to disconnection of

its

generators

or one of

the

outlying

tie

lines

suppi-ving the centre.

The

outlying

tie

lines

can be

kepl in

operation

and

the

generation

output of the

integrated

power

s1'stem

used

to

the marimum

by

timel5r

unloading

of

the

overloaded

t.ie lines and

prevention

of

real

po\\,er

flou's

over

these

iines

in excess of

the

permissible

values.

This

limitation

is

accomplished

by

tiie

power

flou' limiters

installed on

the

tie

lines.

The limiters

perlorm

unioading

operations,

if necessarr'.

\\''th the

net.worh

shorvn

in

Fig. 6-12c

power

fiou'

Iimitation is

obtained

bi'

automatic

reduction

of

the

output

of

the

power

stations

(or

one

station

used

for tite pur-

pose) of

the

periphery power

s1'st,em

supplying

the

overloaded

tie line'

-

The

setting of

the

group

regulator

power

controller

is

controlled

b-v the

po\p-er

flow iimiter. The control

signal

is transmitted

s'ith tlie

aid

of

remote

control

devices

or

b-v

local

controi means.

(bi

Tlie

central

po\rer

system C

is conneci.ed

to tlre

peripiierai

pot'ei s'\'stems

as

shop-n in Fig.

6-1.2b,

the

peripheral power

systems

being

series-connected

to

each

ct,ber

("chain"

scheme).

'Limitation

of

ilo\','er

fiorn's in'the

terminai ties should

bc

performeci b;t' the

]imiters

installeo

on

tire tie lines

so tl.rat, the unioading

of

the

assigned

porver

stations

is

effected

in the terminal

po$'er s5,stems,

depending

ou

rvhich

of

the

tie

iines is overloaded.

Over the

tie line

PL-P2real

power

can

be

transmitted

from

po$rer s1'stem Pl

to P2

and vice

versa.

Iimiter.

Rcrnoving a

dangerous

power

florv

over

the

P1-P2

tic

line can

be made by

the

cenLral

iegulatiirg device

ithich receives

informat,ion

about

the loads on'

individual

paris

of

tlie tie

}ines

from

the remote

control

channels.

For

exampie,

tbe P2-C

tie

line ma1'

be

unloaded lif

increasing

the

ioads

on

the

power

sJ,-

stems

P3 and

P4.

The

fulfilmenL

of

such a

"tliinking"

arrtomatic device

in the

cent,ral

complicate-c

tlie

cle-"ign

and

in

the

cacc

of

vcrv

eomplicated

circtrits_a

is needed to delermine

tlie reguired

load

u'itJr

minimurn

losses.

In

regulat.or

compriter

the first

Reai

pou'er

fiow

}imiters

should

be also

provided

to

unload

the

internal

ties

by

Tmoviug

tbe

load

from

individual

po*.,

planis

;i

;[;

given

power

system'

The

best

resuits

are

obtained

by eianging

the

rea]

po*..

value

at

the

power

plants

electric_ally

close to

thL

overioaled

transmisiion

lines. At

the- present

time

the

AFP

&FC

system

in the

ring integt"t"a

loo,*1.

s5,srems

is

being

studied..Theref:ore,

the

rbone

should

be-iegardEa

"r

a-oersion

to

be

verified

and

studied

additjonaliy.

Som-e

organizatitns

plan

io

ur"

a

hiEh-

'r,Leu

nrg,Jlruuru

uu'rrpurcr

lor

rne

Arro(

rU ogvlce-S

Ol_

thls

rntegfated

pOwef.

systems

with

remote-control

data

input

and

control pulses

outpu=t.

1:4*

I

-l

AtTToMATIccoNTRoLoPFREQUENCY,REAI,PowER'Po.wERFLo.!T

D,I Q

2r2

CHAPTER

SIX

6-7. Magnetic

Power Transducers

An

essential

component

of the AFP&FC devices

is a

real

_po-wer

transducer.

A magnetic

power

transducer

witl no

moving

parts

performs

well and

rellab_IV.

fo_r_t_he

circuit

of such

h

transducer

see

Fig. 6-13.

The cirient

fiows

in

the rectifierc

7RB

and 8.RB

are

proportional

to

sguares of

voltiges

Un

and f/r, i.e.,

ir

:

?U!

and

iz:

lU!.

owing

to the

nonlinear

7o

actualcr

(r)

,Fig.

6-13.

Magnetic

power

transducer

(a)circuit;1T,2T,5fand0?-interveninEtratsfo-rmers;3SI'4SJ-satursblein-

brictbii; tnt'

;nri dFB

-

rectifying.

bridges;

_eR-138

-

series

resistors: 14C-17C

-

capacitors;

(b)

evplanatory-diag:ram;

Ur

:

Ur:

aU46i

Ut:

EIe

charact,eristics

of tlre

saturabie

inductors

J^Sl

and 4.S,r

and

alro to

the

choice of

resisLors

gn-,'lAn

;;d

capacltors

I4C

and 15C

at tire

output of

the

intervening

transformers

5?

and

6?

ol

the

phase-sensitjve

circuit.

From

Fis.

6-13b

Since

i,

=

Ui;

t,

=

Ul;

I4:

[isi Una

=

(Ut:

Uz)

f

r,":

kr

L(l zf

Us cos

A)2*

(Us siB

q)2

-

(U

t

-

Us

cos

9)2

*

(U3

sin

g)zJ

IIShgd

eftnef

agCgfdlng

tO

a

pfeSCfIDeO

Sgue1rule

uI

rr orrr5rtvu

pr

vsv euvJ

prrrooo.t. The

assignei

valuei

are-correct,ed

by

the

frequeDcy

corrector

u'hich

L^ 1-^^^^ ;-

Ires:

kU

aBI

6

cosq

where

ir is

the

proportionality

factor

which

is

controlled

by

tap

changing

on

the interiening

transformers

7-T

,

-

27, 5T

and

6f

.

6-8.

Conclusions

1. Automatic

control

of

fregueDcy

and real

power improves_the

power

gua-

Iitl'

and makes

"cono*i.,loading

of

the

generating units

possible-

This

control

is

ieasible, if

a spinning

reserve

of real

p:ower in

the

pow;r

systern

is available

and

the

tie

links

have

sufficient

transnission

capaciiy

so

that

the use

of

this

?6c^?rro ic nnf hindororl

r 99Vl

t

t. The

primar5'

ipeed

goarernors

of

the

tr:rbines

-instalied

on

each

genera-

tor-turbine

unit

"t.-ir..ot"ial

operating

eiements

of

the

gele-ratlng-units

and

eniure

their operation

in case

bf

changes

in-

the

electrical

load

of

the

gene-

1'"torr.

The

piimarl'

,0..U

governols

(generaill' centrifugal)

act

on

the

steam

i*"ir.l

i"ppi'

t,o

ttre

iurUiie

via

a

speed

changer

and

determine

the

primary

reguiation

characteristic,

i.e.,

the deper

-

3.

For

the

generating

units

furlish

and not

incliided

in

the

gfcii:p

control.s

ges

in

the external

load

is

inversel5

I

iient

of

the

regulation

characteristis.

l

a

group

control

system

the ioad

may

t

eiectrobydraulic

or

electromagnetic

col

governing

devices.

'

4.

Wf,en

a

spinnigg

reserve

of

real

po\l'er

is

avaiiable

i!

a

large

po\rer

s-vs-

tem

the

freguencl'lrT*ta

stable

at

the nominal

level

b-v

the

combined

action

of

the

primary

ipeed

golu"roor=

gf

tle

parai)eled

generating

units'

Tiie

larger

iUe rating

of

ihe

po\^er

s-vstem,

the

less

the frequencS

hunting

about

the

mean

vaiue.

5.

When

the

machines

of

a

multi-u

system

the

given

power station

ma]'

as

a

united

s'hole. The

ioad

is al}oca

by

tbe

equalizing

s1'stem

with a

preassi

generation

or

on

the

basis

of

equaiiz

(costs) per

1

kW

of

generation.

6.'The operating"conditions

of a

powql

s-t,atlon

srith

a

real

power

group

control

system

depeid on

the

power

controlled

setting-'This.

setting

is

accomp-

Iished

eiiher

according

to

a

presc;ibed

scheduie.or-is

assigled

b)'.the-..Yll

T

r

L"tl

;l

-:4

ur:/1ffi2

and

The

resultant efiect

of

the

power

transducer

at

the

input

of

the

actuator

unit

is determined

by

the

resultant

current

(6-12)

-13

et,ermlnes

tne

relatron

the

networks

delivering

count.

,\.

-I

l-

t.

-\

l+C

l\

\

r,

t-.r

l\

tA,\

lru.--

/

-------+l

-_=

A,

/

i-r rsn I

U5

t0E

/res:

iz-it

(6-14)

iro*tt

fo'the

po\*'e;

system

also

being

taken

into

ac-

214

CHAP?ER

SIX

AIITOMATIC

CO}TTROL OF FREQUENCY,

REAL

PO\\'EH.. POWER FLOlf,'

or

(

7'

At

the

thermal

stations

t\e-operation

of

the

real

power

group

control

devices

should

be

coordinated

rvith

ihat

"itn*

autonaatic

heat

controi

devi-

ces'

The

electrical

]oad

-9f

"

generator

must

not

be

nfirr.r-tnan

the

turbine

entr5'

steane

pressure.

when

the

load

suddenli

drops

the

automatic

safety

devices

should

not

function

and

the

generatiog-i"it

must

continue

to

operate

(withih

the

range

from

idling

to

suppiyiog

inr-house

circuits

of

its

orrn po\ver

station).

At

the

Dower-

stations

responsible

for

district

heating

the

AFp&

Fc

det,ices

should

not inrerfe..

*i*

;hJ;;;*"l

h;;tG;t;.

6' At

the

hvdroelectric

.portrer

stations,

the

\vork

of the

AFp

&

F.c

devices

should

be

combined

with

the

action

of

the

automatic

controis

connecting

the

stand-b'

generating.units

(either

shutdown

o.

"-"ra

";

;6-h;;;;;,

eapacirors)

to

the

sroun control

s-vstem

when

the

powe.

.vrt.*

f

*de;;i

ial1s

to 4g.g_

49'7

H; or

ivhe'r

the

siation

itttt-geneiatio;

t"

properly

cover the

specified

Ioad

schedulg.

When the frennon.,r, folle r^ Zo K rJ- +l^^ ^^rr^- -r rL- -

rol etevic.e

must

autom.qti;fi;;i"*;;": ::;;i:"--:i::^","::":-"_'-

'i:

€roup.conr-

wrvqrrsv

vlauBtr

uu

a seLLrllg

\YIfICJI

gnSUIgS

tng

maXImUm

generat.ion

of

real

power.

I'

The

real

power

group

control

devices

and

the

load

schedules

for large-

rated

therrual

stations

not

-envelo.ry.ed

bV-

u

gro,rp

control

.i,.ir*,

take

it

pos-

sibie

to

run the porver

system

wi1]ioqt'freq:.,"nf

interferen;;

b),'tle attending

personnel

to

the-

operation

of

individual

power

piants

""a

g,J"*tating

units.

Economic

and

reliable

operation

9l

u

poiu"'riiri.;

is

depeud;;;;,

a ri,er]

de-

'iiene.d

loresigirl-

Ioad

scheduie.

TJnscieduied

r:ariations

in the

i.;J

i"A"iirt

the

dail-r:

ioad

schedule)should

not

er-ceed

3

percent

of

the

p1""i.J

load.

10'

Unscheduled

loads

mani-fest

themselves

br'

"

"U"og[-in

lt"qu"nc-r:

from

tiie

rated (preassigned)

value.

Unscheduf;d

lo;l

variations

and

reestablishment

oi' tire

frequenci'

is

placed

rvith

a

smal]

number

of

frequencl--reg"tuting

po5,er

stations

rrhich

mus-t, possess

a

required

flexibie

polef

reseive.-F'or

this the

most

suitabie

are.hvdroelecfric

po\r'er

stations,

ihen

u,ater

storage

and gas-

tur]:ine

Dower

slations.

Less

suitahle

for

the

purpose

are

tiie po#erful

gJne-

rating

units

of

thermal

stations

as

load

changei

have

to

be

combined

u'it.h

the

operatioti

of the

automatic

heat

control

deiices

which

g.ort"n]'

results

in

uneconomical

operation.

-,,11'

If

on}-v

one frequenc-y-regulating

hydroelectric

power

station

deals witii

tne

removal

of

an

unscheduled

load

burden

one

frequencv

regulator

at

the

station

i-s

sufficient.

The

"increase"

or

"decrea.se"

effeci

of the frtquencl,

regu-

lit:_l

oo

-tht,gto,Yp

control

system

must

be correcred

to

the

value

ot

r"uf poi.,

rlows

ot'er

the lines

c,onnecting

th?-po\\'er

station

u'ith

the power

system

and

stopped

b-v

the

flow

iimiters

insfailed

on

the

tie

lines.

t

12-

When

several

regulating

power

stations

are

used, to

remove

an

un-

scheduied

load

from

the

fower-sj"tel'',

they

ma-v

be

operated

by a

group

control

syst'em

from

the

load-dispatching

department

of th6 power

systEm.

The

real

The effect

of

the

power

flow

limiters

on the

central regulator

should be

backed up

bl' the

local power

flow

limiters

which

determinerlhe

critical value

ol

19"1

power

transmission

from

system

to

svstem

(the

power

"balance"

oD

the

i;ie

iinks)

ald effect

the

unioading

of tire power

pianis

in the

given

po$rer

system

to

i.imit

t!. power

florvs.

The unioading

of

-po*'er

planti eleciricail),"*lose

to the

overloaded

tie

line

is

most effective-.

6-9.

Review

Questions

.

Eac.h

power-station

assignnent

is

corrected

iy

a

frequency

corrector

which

stops

the

transfer

of

control pulses

when

the

freguuory^

decreuses

or

increases

5' Substantiate

the

expediency

of

automatic

reconnection

of

shutdo*'n h'droelectrjc

generators.

when

the power

syslem

freguency

falls.

6. What

is the purpose

of tbe

turbiire

speed governors?

\[rben

the

eJectrical Ioad

on a

sene-

rator

increases

does

the

priman'soeed

sovernor ine.rpqsa nr rtanraqca rho +,,-r il]^**^I'j:,:--*i,

7'

What

are the

1$-ulalinq

characteristies

n

=

p (P)

ensured

by

the

prirnary

speed

governors?

t!h.at

is the

sleady-state

coefficient-oi

thes'e'ch'aracteristics

and

its effect

on the

allocation

of

load

among

paralleled

generating

units?

216

CHAPTER

SI.X

C/t,a,pter"

Se,r-en

RAPID

PARALLELNG

OF.SYNCTIRONOUS

GENER{TORS

AND

PARTS

OF

POWER

SYSTE]If

7-1.

General

.To

prevent-

or

eliminate

faults,

the

rapid

connection

of stand-b-v

generators

:*

*'-ff:I" *:q:* :j^ :i::Tl::.," t:. :

p.._.t

9: ?

i th;

-p;il

;-i

il ;

-

;;

;

;;

;;;;^;;';;;;

"-*^":_^1:::":'r'Er'r-

Lrutr

tu

asYusrLronou_s

operatlon

are very

riiiiiui-LaiiL'

iil.

iiii-s

conneei.ion

speeiai

researches

were

undertaken

to

find

me--

tbods

s'hich

would

enable_

synchionous

machines

and

prrir

o1

iU. po*",

svstem

Pl._

qli:ti_y,

automatical

rt'o

paraliel

optration

when

rne_p_ower

s5'stem

operate

and

voitage--

Srhen

the

power

statio:

:rate

undei

oor*"1

operat_

i:q..T:9lli?Tt

parallel

co:

nerarors

and

compensators

navrng-stgting_

motors

is t ,

the precise

syncironizi-ng

methodst?-11.

In paitid,ula

logeneraiors

q,ith

indirect

cooiing

of the

windings

workin-g

into

the generator

r'"olt"g.

iusbars

and

also

to generators

with

directll-gooled

u'inding:s

"o6

-c5'Dghroious

macliines

g,ith

rl'inding

reception

slots

or the

rotor.

.Accurate

synchronization

is effected

s'hen

the

follou'ing

conditions

are

satisfied:

ed

below

makes

the

worb

of t["

!!9r4!!r.

-

@-

., -r

prop"t

opera-r

"i"d-"i,

and

voltage

aud

when

the

frequency

falls

to

45

liz

and

the

amoiitudes of rhn

au(I

Yorrage

aDo

wlen

theJrequency_falls

to

45

IIz

and

the

ampiitudes-of

thb

voltages

being synchronized

vary

*'ithin

*15

per

cent

of the

rating.

The

great

CEAPTEN

SEVEN

R^PID.

PARALLELI}iG

OF

SYNCERONOUS

GENERATORS

AgCg+ /t0

y -tla

u

+cc

advantage of the ACT-4

synchronizer

is

that it

uses no

vacuum

tubes

and is

(o)

direct

start;

(b,

c)

reactor

start

the'

action

of

an asynchronous

torque.

When

a

hyposynchronous

speed

is

reached

the

motor

is

pulled

in synchronism,

as

with

an increase

in the rotor

speed the

current in the

rotor

winding

and the

torque

rise to

the input

value

(which takes

place

when the

s'inding

is constantly

connected

to an

exciter)

or

after an

abrupt

increasing

of

the rotor

winding

current

produced by

the

starting automatic

devices

Ii-3], t7-11.

control

systems.

7-2.

Preeise S1'nehrcnization by

Means

of arr

LCT-4

Autosynehronizer

The

type

ACT4

synchronizer

gives

a

connecting

pulse

during

the

interval

when

the-

6mf

vectors

of

the incoming

machine

and

the line

voltage

approac.h

each

other,

i.e.,

when

the angle

6 changes

from

270to 360

degrees. The

control

signal sending

point

is select-

ed

so that the time"of

switch

closure

is

taken

into account.

i.e., that the

contacts

of_the

sv'itch

are

made at an

angle

6 ciose to

360 degrees.

In

this

case

the

excessive siraft

torsue

of

the

machine

is

small

a-nd

the

generator

achieves

syncir-

ronism

at

once

rvithout

hunt-

ing and

rvitirout

asvnchronous

runnlng.

If the

time

from

the

instant

the

signal

is

senl

to

close

the

srvitcb

is

constant and equals

f"1, the

svncirronizer

mus'i

pro-

duce

the

controi

pulse

treed:

:

lcrs before

the

angie 6 rea-

ches

360 degrees,

i.e.. the

con-

trol pulse

is ieading.

The leading

time

is con-

stantlf

independent

of

the slip

frequencr-.

\\'ith

the type

ACT-4

synciuonizer

the lead-

ing

time variations

do not, ex-

ceed

3

electrical

degrees at

frequencS'

differences

ranging

from

l"

:

0.25

Hz to

.1,

:

:0.A4

I1z.

The essential

elements

of

the

ACT-4

synchronizer (Fig.

7

-2)

are

a

differentiating

trans-

former,

a lead

relay,

a

frequen-

cv difference

control

relay,

a

Di.{ferenttol

!rans.former

and

leod

reloy

freouencu

-

dtflereicp

eenira/

relay

i/uicage-

difle:ence

rcntro{

ret,ay

luxiliary

relay

fxeculion

r:lay

Clcsino

circuit

Slip relcy,

..less"

TLtrtJ

reloy

Fig.7-2.

In[ernal

connection

of

t1'pe

ACT-4

auiosynchronizer

I

througb

s

-rectifiers:

o

-

lcad

relav

(LR -

polarizeC

rela-v);

z

-

frequenci'

control

relay

(FCI?

-

polarizeci

ielayi;

6

-

voltage.control

reiay

(VC.p

-

do-

tarlzed

rela]):

s

-

auxiliary

relal

1,4..R;

J?

-

auxiliary

relal- 2AR:

jt

and

le

_

slip

relays

(F

Sj? anii F,{.R

are auxi

liary

relay);

.j4

-

inteivdning

trans-

lo-rm.cr;

JJ

through

ls

*

capacitors;

20 through

40

-

resistors:

ct

-throuetj

J6

-

bridges

and

su'itcbes;

BC

--

|

"7C

t7{U

-fn-/

--,ftn-l-;;-TcPj

;R-t

z,i

CR-Z

ttp

L'CP':

>rIr,l;-7

2AR-t"n9ffr

?, |

,,/,

?---\i-.1

n

_/i:

_-

H

5+

, IIP-I /.24-i'2 zAE

yci

-ffieT).

?c-r1 /-

,2.

2AP-3

*

t'"';

To

close

syitc.l

r<o-t t/

TR-t

..

t9

r5P-2

7p

L--z-#,JLa\)

rA.+'2

block-contacts

ot

iwiiib

FSR.4

Tc

speed

CEAPTER SE}-EN

RAPID

PARATI.FT.ING

OF

SYNCERONOUS

GENERATONS

221

Yoltag€

difference

coutrol

relai

and a device

for

frequeney

alignment.

The,diffe-

reutiating

transformer

and

the lead

relay are the

elements

which

create

the

con-

stant

lead time

of

the

control

sigtai with regard

to the optimun

point,

i.e.,

the

instant

when

6

:360

degrees.

Fig.

T-3.

Diagram

explaining

operation

of lead

rela-v

J

-

Yoltage

across

s@ondary winding

of

difterentiating

transformer

The

primary

wind.ing-

of trlnsformer

-/4

having

a

core with

an air gap

is

connected

to

the

-beat

voltage..

First,

the

vcitage

ii

rectified

b1, rectifier

-Z

and

,

In

expressions

(7--2)

and (7-3)

/q.and

/cn

are

proportionality

factors

whose

values

are

controlied

by

adiusiing

reiistors

io,

it

io

zB

and. zg

In

compliance

with

qZ-i;

the-crurenrs

are

ir

aR:

k'zlJ

"tt"

(#

)

tz

rn:

-h220,$

eos

(+)

smoothed

down

by capacitor

i5.

,uLlleo

uowo

Dj capacllol

li.

During

each

beat

cycle the

rectified

volta

.

uuHn€

eacn

be€t

cycle tbe

rectitied

voltage

continuousl\'

changes

its value.

As a result,

an

emf

is

induced

in the

secorrdaiy

winding

of t.ire

trarisformer.

The

secondary

voltage

changes

its poiarity

at

the

maxinum

of the

secono.ary

voltage

changes

its polarity

at

the

maxinum

of the

primary

voltage

and,

when

the

pha-se

vectors

of the generator

pfrurary

vorLage,arro!

wnen

rne

pna_se

vect,ors

of the generator

and circuit

emf

coincide

reaches

its

maximum

abplitude

(Fig.

7-3a).

.

If

the generat_or

-em!

E,

equals

the

citcuit voit.age

trc then_

in conpliance

with

the

diagram

in

Fig. T-4,

the

vorrige

appried

to the primary

winding

of the transfoimer

LU:Z[J"sin$:zu,sin

$

-2U"sin

(ry)

fl-rl

where-<0"

and

f"

are

the

anguiar velocity

and

beat

frequencl,

with

slip

s.

The

current flow

in

coil

I of the

polarized

relal'.L.R

(Fig.

7-2)

is proportional

to

this

voltage

ir

r,R:

kAU

.Tire

polarized

reiay,Lr?

is

connected

so

that

when

the

current flows

i'n

and

B

are

equal

tt

zn:

tz

r.n

the

relay

contacts

drop

out.

As seen

from

(7-4)

and

(7-5)

condif.innq /T-A\ raLoc -to-o -,1,o-

\

_r1

____---vsv

\'

v/ uqavr

|-|rqv9

t.tttvx

ii,z[i,sin

(+):

-

kzZ[J"]

co,

(+)

i.

e.

tan(#):-#+

small

''

tan(E)*#

t:

-+:

-ks:const

Ua

:

beat

rd

out

before

the

angle reaehes

360 de-

and

.

\['ith

angies

6

being

hence

thus

(74)

(7-5)

coils

L

(7-6)

(i

-7)

(7-8)

(7-e)

(i-10)

wnere

+:

-#;+

Fig. 7*4.

Expla-

natory

diagram

CoiI

^B of

the

relay

LR

is connected

to the

secontiary

*'inding

of

the

differen-

l!3

no,t.ibility

of

determining

the

lead

time

f

1,o4

from

the

condition

of

(7

-2)

(i-3)

Iength

value

(7-8)l

.volragel

,""

n.liriru"#Jrik.

l;i:

ff".i

?:lr;ff$."t'"7'^

Iine

substitute

for

rhe

beat

sine

curve'U;:

f1;l-;^;

rhe

zero

7-3b)

Ithe approximate

assumptior,

,orr*lpooai

io

assumption

-. '

a$U)

e2

LR-

-

-z-61-

of

straight

poinf

(Fie.

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

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