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

ta.

CHAPTER

FOUR

AUTOMA?IC

CONIROI,S

FOR

MAINTATNING

STAIILITY

143

?TR

Yloj*

op-erating

time

can

be

adjusted

from

10

to

15

s

or

0.5

to

3

min.

The

relay

zl'IlwlIL

close

itscontacts

oniy

in the

case

of long

asynchronous

operation,

as

restotation

of

normal, paraliel

operation

stops puljation

of the

staiting

ele-

ment

contacts

making

the

relay

J?^R

function

and

the

relays

lAR

and.'pTR

reset.

.

Figure

4-40

shows

the

circuit

of

a

device

utilizing

the

above-described

opera-

ting

princllle

with

starting

voltage

relay-s.

To ivoid

unwanted

starting

at

faults

in the

voltage

circuitJ,

two

se-ts

of voltage

rela-vs

r.r1..a.

The

6ffi ana

rncludes

powerful

hydroeiectric

statjons

,w-power

thermal

stations.

Most

of

the

delivered

through

tie

lines

to

the

,..*i_

disconnected,

the

hl,droelectric

station

i

power

station.

The-hydroelectric

;;;;

^--4^- i -r 1 1

svstem

of the

hvd.roelectric

qenpr-.r^?6

+c=: ---+

have

time

to

.rtiily;j;i;

;h;il:;a:iJ#".:

nse to

120-130

per

cent

of

the

rating.

The

normai

system

regulating

the

speed

of

hydr6electric

g*;:

rators

allows

for

this

increase

as

they

"r.-lo*_

speed

machines

and

this

speed

rise

ii

not

dan_

+

Vr)

be taken

into

consideration-

The reoui

7.TR

relays

ale

for

control

of

both

the

closed

and

opened

states

of the

starting

elements

u-nder

aslmchronous

conditions.

The total

period

during

which

thE

device

controls the

asSrnchronous

operation

is

determinbd

b5,

the

set?ing

of time

rela5'

5.

As

a

resrilt.

of

increased

speed

of

the

hvdro-

eiectric

generators

the

turboseneratoi.

i.,;;;;

rIIe

Irelfuency

relay

connection

circuit

controls

the

operational

current

circuit

by

the

contact

oi a.voltagr

t"l"y;hi"h;;Iosed

at the

existins

volrape

j_

i{l

operatrng

setring

voltage

is

70

to

g0

per

crrcult

employs

a

voltage

relay

because

the

fre-

contacts

and

make.

the

outpu{

relay

misoperate

g€rous.

cent

of

the

rated

value.

The

lrng

individual

sets

at the

opposite

ends

of

the

line and

giving

them

similar

set,-

tiogt

or

by fittingthe

sets

at-different

points

of the nettork"giruiog

them

selec-

tive

operation

ability

which

is

obtain-ed

either

by adjustmEnt

tE

a

different

Fig.

441,

sectionalizing

device

detecting prolonged

asynchronous

operation

guency

relays

may

close

their

due

to

interruptions in the

applied

voltage if

a

fauit

occurs,

for

instance,

in the

circuits

of

the

voltage

transformers.

To

prevent

overspeeding of

thermal

turbiues,

a

proposal was

made

to simul-

taneousil'

disconnect

the

generator

from

the

power

system when the automatic

safety

device comes

into action. For

this, the

circuit

tripping

the

generator

switch

gear

must close

when the automatic

safety

device operates.

As compared

to the

use

of

automatic devices utilizing

a

frequency

responsive relal',

this

method

i: less

perfect

as it

predetermines

tbe

stopping

of

the thermai

prime

mover

even

in

the

cases

when the automatic safety

devices misoperate.

Automatic

control

devices

responsive

to

the frequency

increase are

installed

not only

on

the

transmission iines

between

thermll

and h1'flloeiectric

power

stations, but on

the

hydroelectric stations

too.

Their

function is

to

disconnect

the bydroelectric

generators

with a

view

to

preventing an increase

in

the

fne-

gueDcy after disconnection of the

tie

links

to

tbe receiving

system. These

auto-

mai,ic devices aie

se*r.

wi-"hin

51,.0-51.5. Hz,

i.e.,

somewhat

lo*'ei

tban

those

of

ihe automaiic

sectionaiizing

devices

insi,aiied on

ihe iinks

io

'r,he 'r,hermaL

s'ua-

tions.

Th':s,

tbe latte.r selves

as

a stand-b1: and e.ornes

into ac.tion

if

the

fre-

guenc], responsive

automatic

device

instalied

on the

hydroelectric

station turns

out

to

be ineffective or

fails

to

function.

The circuits

employed

by the automatic

devices designed for

disconnecting

the

hydroelectric

generators

when

the frequeDolr

1!sss

are

simiiar

to those des-

cribed above.

4-7. Preventing

Misoperation

of Protective

Rela;'iag

Since

the currents and

voltages encountered in overloads,

syuchronou-q

swings

and

as_vnchronous operation

are commensutate

u'ith the short-circuit

currents

and

voltages, all

type

protection

devices,

except differential

and

t,hose

respon-

sive

to tire

backward

and

zero seguence of

eiectrical

quantitiesi

can

function

under

the considered operating conditions

without,

short

circuits.

Subject

to the

tive the

profective

device

wiII function.

Misoperation

of

protective relaying is

prevented as follows:

(a)

Bv

the use

of

special

blooking

units

("swing

biocking")

which

detect

short-circuit

conditions

and permit in

tiris case

protective relaying operation.

When

there is no short circuit,

the

operational

circuit

of

the

protection remains

open

regardless

of changes

in the

electrical

quantities (increase

in current,

dec-

rease

in

voltage).

sensitivity

to

the trsxv)'

load

protection.

Example-q

are

tbe

(b)

BV

using devices

which

possess reduced

cunents

as the

starting elements of

the relaying

-e

contact

opens

oni['for

a

short

t6e.

.

OpgSing

(if

only

for

an inst,ant)

of

contact'4-I

of. the

st,arting rela1,

deenergizes

the

coil

of

auxiliary

relay

/

and

makes

it

complete

the

piotection

circ"uits.

Relay

J

is

chauged

over to

the initial

excited

po=itioo

afte;

the

actjon

of time

AUTOMATIC

CONTROI.S

TOR

MAINTAINING

STA3ILTTT

T..

of.

voltage

relay

blocking

units,

and

distance

starting

elements

having spe-

cial

characteristics.

u r^q

rrs6 urrrereuu

\JPErd

Ur.!E,

Dsl,l,IffHD.

DUG!]l all

t,ltt-

monl ao- l'o ^}.+^i-^,1 l.., ^^*-^^4:- - -^1- --- r - r'l- -

"

ueuu

uq!

se uuuarrrvrr

rry

urjrlrttruLr[g

I'eraYs

(.(]

llle rnsllumgnL

llanslormgrs

t,nlo-

ugh

a

differentiatins

network.

I-n-

practice,

cwreit

and

impedance

relavs

of different

sensitivitl-

have

been

r:sed

for

the purpose.

Service

eiperience

hai

shou'n

that

the devicei

ma1' miso-

perate

fiien

tbe

electrical

quantitjes

var1,u'ithin

a time length

}ess

than 0.?

tg

1

..

Therefore,

the

blocking

units

used

in

the

USSR

operate

on anotber

prin-

pr

ciplg_ which

has

justified

itself

over

manri

-\'ears

service.

145

t0*2076

746

CEAPTER

FOUR

AUTOMATIC

CONINOLS

FOR

I4.{INTAINING

STABILITY

747

relay

3 whose

setting

exceed.s

the

time

for

clearing

,the

fault

in the

protected

zone

or.it' is greater

than

the

time

for indicating

thJ

fault

in

the

protected.

zone

in

tbe

instantaneous

measurement

schemes.

rf,e

voita;;

tt;J

ffiedaoc

e

Im

reia56

gua$

against.repeated

making

of

'the

protectioi

circuirs

rf;;;iu;rir;

a

slmmetric

short

circuit.

Contact

4-2 af the

starting

relay

prevents

the

biocklng

device

from

repeated

starting

after an

aslmmetric

short

circuit

is

cleared.

To"make-the

circuit

op"-

ration.

accurate,

r^elay 2

is provided,

in

which

the

armature

return

is

delaved.

br'0.1

to

0-2

s

after the

reia-v

coil

is

deenergizJ.

-

--

The

deviees

s'hich

start

tbe

protection

system

wiren

backward-seguence

crurents

and

voi

ta ges

appesr

a".,ooor.tta

.i,''il"*'

ioiG;il1r;:;i"-.";;

;;-

tff

;;iward_sesuence

current

and

voltase

filters.

Let"us

";;rid;;

lh";;;;il;;'of

a

resisrarcFcspacirance

filrer

or

backward-sequince

ooii"ffi

i;liJn

;t

"it;"d.r*;#

tos"th;i;itl-rfJ

brockingunit.

(o)

L4

L1

R-

-z

n

-

icB

*cz

(4-2s)

I

tAE

"!

(a)

circurt

with

instantaneous

readine*s

for.

repeated

operation;

tUl

circuit with

readi_

nerF for

reFeated

operatron_after

preaesrgaea'timd;

.l

-

auiltiar-r

ilray;

r.

,

_

time

relays;

1-r

and

r-s

-reiar

*,ll1gs_-tuwonoiil-to

ssluuBerry

in

eredtrical quantitres;

v,

rm

-

contacts

of

voltage

or

impedance'retat

-(poiitioii

or erintlcG--coiiiipdnos

-iii-i"iri"isirud

state

of

relar)

The

device

circuit

prevents

improper

functioning

of

the

instantaneous

pro-

tection

devices

in the

unfaulted

paf-ts

of

the-

poo'er

system

in

case

of

synchronous

swing

.or

as1'nchronous

operation

due to

iti-timed

""trrriog

-;i;-;;"rt

circuit.

In

s.uch

a

case'

the

proteition

is

taken

out

of

operation

afier

a

sufficient

Gt

;

(a

)

i6i

4-43.

swing.

and

overload

blocking

circuit

re.sponding

to

asymmetric

elec-

rrical

quantitie.c

(thougb-

of

ver1.

,nbrr

au"?tlo"i

-qlJav

of time

for it

to

act

in

the

proLect,ed

zone.

This

time

is

0.2 s

ior irrrrrnt"ouorr.

circuit'to

repeat

the

operation

muit

rne

dlsadvantage

of

the

iatter

version

is

that

tion

of

lightning

arresters)

the

instantaneous

Fig.

444.

Resistance-capacitanee

firter

for

backward_sequence

voltage

(a)

circuit

dilry?T,

(b)

potenti_al

dBT,"T-_y!"n

torward-ee,q^ue-nc€".vgltgse-.is

applied,

to

filter;

631

sane,

when-Eaciwaro+equence

yortage

ls

appried.

to

,iiter

For

the

diasram

of

tbe

fjiter

see

Fig.

4-44.

fu

orcier

to

mg.ke

the poteatials

at pointsm

and

n

equal

a-nd

prevent

t[.

t-"irv^9-"nieci*a-to

iur.i

p"iorc

r-t-i-rri;;;"g

to

rhe

zero-

l*

l"#fft^:,:.tT."i""ril{t"F;,

-rh;"fii'ter

is

.o"o""t*a-

io

the

irterphalJiolrages

and

rhe

R1

: zg1:

rczi

*r:

+

,

+

(e)

length

of

time

is insufficient

t,o

allo*,

li.

r"ppr;,-;;i-;;.|"r.,""r."

ar hea'v

tholr,^:il:lill:

to

part

r,o,t]r"t

misoperarion

oi-fi,e protecrion

i.

r*ougrit

"^ir"r;.

Tbe

circuit

in

Fig.

!-+1o

provid'es

instantaneoui

readiness

of

the

protection

after

clearing

a

shorLcircuir.

The

circu-it

in

Fig.

rr_+{U

p;r;d.r;.rJio*r,

of

the

device-to

operate

repeatedly

after the

lapse

of'preassigned

time.

t1 ttri.

event,

no

undervoltage

or-

inepedance

relaf

is

required

and ihe

readiness

time

of

the

The

mentioned

ratios

are

ilo=

-l'"o

I

Ir

a

dead

(merar-to-metar)

ehort:;;;::JJ,

where

'AB*cl

fn

pouier

system

may

be

put

out

of

action.

Such

us

o:

&ec

b=i

l{ec

c:0

r-

-AUTOMATIC

CONTROLS

FOR

MAINTAINING

STABIITITY

749

then

the voltages

appear

t

T't

When

a short-circuit

oceurs at

a certain

distant

point

X on

sulstation

G

the

residual

voltage-

is not ecuai

to

zero.

fherefore,

a

appears

in

this

event

at the

begiuing

of a symmetric

shoit

the busbars of

a

supplying

backs'ard-sequencs

vbi ta

ge

circuit

u,

o:upho

uy

6:

uph

b

u7

":

uph

c

I

l

)

(L32)

vl:o.s

(u

pn.

m-19!^rro*)

(+u)

-

In

expressions

(4-30)

to

(4-32)

i^. aDd

unr ar€ instantaneous values

of

short-circuit

r:urrent

and

pbase

voltage

under

prefault-condifiijns.

"Fig*.

4-45

ilustrates

hou' the free

currents and voltages

var],

in time

from

the

instant

the

faulr"

occurs.

The

current

and voltage

sj'stems are codsidered

separately. The

diagram

in Fig.

4-45a corresponris

to

the short+iriuit

instant at which

the I

pLase

cuirenr

a-plituae

I^

T,

t

urt

(t)

Tb

currenLs.

current

and voltage at backu'a/d sequence

can

be

easily

determ-

To

simplify

the

anaiysis,

assume

secondarv terminels nf thp filtnr

rrc

voltlpel-

aooii t[; ;;;r;i t.';. 7:

as

follosrs"

r

--- -

-r

s'here

?r and

.?"rt

U

cilt:O)

and

uc2(t:0)

The

constant

Tt

:.rRt{

that

the relal'resistance

is

inJinite

in value,

i.e.,

tbe

open.

\

and C^ rrndor fho nrofottlt n-nnrlif inns nnp rla{ominorl

---

-z

(437)

(4-3e)

uently

Fig. 4-45. Free currents,

voltages

and backward-sequence

componenls

on

secon-

dary sides

of

instrument translormers

during

s1'rnmetric

three-pbase

short

cir-

cuit

in

po\r'er

system

is

at its

maximum. Figure 4-45c

shou's

a sbort circuit arising at

the instant the

A

pbase

current

amplitude

is

ai 0. Analogous diagrams

for

the voltagds

are shon'n in

Fig.

4-45b,

d.

The s5'stem

of free

currcnts

and

voitages

at the

instant

thel' 211t.

is asymmetric and

a surg€

of

voltages occurs at

the

output

of

the

backward-sequence

fiiter. The

induced

curreits and

voftage-s with a three-phase

short circuit &re s-vmme.tric.

Therefore

the-v

*.ill

IJ

ct:

{u

,.r.i*

(4-85)

iru

[Jcz:

]'2"

Uspr-i3o

(ffi6)

.

Th.e

voitag'Q

acrcss ilie

open

terminals

of tbe

filt.er is

detersrineC

by.the value

of tle

projectionofthevectoi.-sum-oftirevoItagesUcrandi;c,'ontheeds;Jordinates

Li*":T

U

7-sri6o

+

+U

spriso

i

^n

:0.Se-joo

(tj

on

*l[

3 ii

"

re*

iao]

vhere

tlr*

tiorr.flnd

i""

^r,

the

effective

r.aiues

of voltages

In

time t

the

instantaneous

values

of the

voltace

across tbe

filter

terminals

u!!)n:

ucr(ooJr-'/',

+

urr(r*'ye-

t/?$

(4-Bg)

:

time

eonstants

of

circuits

I

and

II

:

instantaneous

vslues

of the voltages

across

tbe

capacitors

at

the

instant

a

short

circuit

oc,curs

is

T7:

C

1R1

where

ct:-L

-

@xc!

Since

.R, i

rCr:

8,4:

Vt:

f., rhen

ZL

U

rtl

i

1

AL

for

their effect

Tbe

initial

ined

on unbalance

value

of

free

Iz:0.5it

c:0.5/"c. -

(Fig.

445a)

4

I2:|

\6:0.51sc.

-

(Fig.

445c)

vo

1

[12:*

uJ

b:0'5L

pn.

*

(Fig. 445d)

vo

(&33)

rr:!-tW-:lf

3:

o.oos5

-

of{r

(l)

where

I*.,,,

aud Urh.^

are

the

maximum amplitude

values

ol the current and voltage.

150

CEAPTER

FOI'R

AUTOMATIC

CONIROLS

FOR

MAINIAINING

ST.ASILTTY

151

Tbe

constant

?rr

is

wbsru

Since

R2t

zs2:!

,

+:t

:{8,

then

scz

:VE

A

r,

consequently

rn:+

*:d6-o'oo18b

Shou:r

in Fis'

4-46

are

tbe

curves

illustrating

how

the.voltages

across

the

rn

and

n term-

inals

deeay

with-

time.

E".o

i' thJ-*r"

of

the';;;t

-riiJavourable

phase

combinations

oJ

The

underimpedance

protection^-qrill

not

respond

to

the

currents

and

vol-

tages

of aslnchronous

operation

iJ

its

*rtti"g'-'

(440)

ztcr

(442)

pedance

from

the

rela,v location

to

the

)m.

;ion

at

swings

and

asynchronous

ope_

:ial

starting

element=

o,hieh

in

conjuno_

iscn

:-.:rt,

rcquceu

respolse_

to

eunents

arising

,I

-

tf I

urt

-U*"

^tP'

-'

-

-'tFU/

At

'n

U^c=U

.. -,e'

.1.

ani.t,i;),

k)

Fig'

4-46'

Voltage

variation

across.

secondary

terminals

of

filter

(Fig.

a-a4)

with

three-phase

short

circuit

ai

prima.y

t""*io"ii--

(a)

Ucz

(f:0r

:

0i

(.b)

Uct

u:0):

0i

G)

IJmn

(r:oi

:

0

vollage

vectors

during

a

short

circuit.

*'hen

the

initial

value_

of.

u^n

is

n_ull (Fig.

4-45c),

iilfi,lt$';'fr,fij:]t*"

"loul

r o

p".

"'""t

ofti'"

l"';;+h;;

volrage

amirritude

appears

across

.

To

irnprove

tbe

sensitivit5',

use

may

be

made

of two

vollage

filters,

one

connected

to

phases

A,

B,

and

c and

the

oiher

to

ph"asesB;-e;

;;j;

or

c,2 ana

Fl

tl the phase

com_

binat'ion

is

unfavourable

for

iiir

]i""t'r,ft*r,

-rir"i'f;i;fr

second

filter

the

minimum

varue

of

t'he

initial

voitage

u-,,

wilr

ne

l/-an

oi tb"

i;;;ril;..

volrage

ampritude.

rn

a numDer

oI

cases

it

is^possible

to

discriminate

again-st

the

currenrs

appea-

*lt-;:::y::^1'"*:_u-:

operlti'on

even

"'iiuo"iJir*-urc

of brocking

devices

made

for

the

purpose.

For

example,

a

current

curout

*itt'i"ot"ruiilTi:

;:#:iXfr:ff

operation

currents

if its

setting

Il[o:ktukzl

cos

(g-z)

*hg:.

M6

and

Mo

are

the

braking'and

operating

When

in

balance,

neglectinl

rTie

f;icii;;-;;d-

tt,n

ac!

6)

k)

)

r

4-4s)

I

torque-c

on

the

relay.

spring

effect

Iop2k"I^.

o.o

whgre

k"

:

safety

factor

equal

to

I.I

Lo

1.2

(4-4r)

are

180

degrees

apart

vectors

ulko

:

--=:

C,OnSl

1

cos

(g-cc)

k1

T*

AUTOMATIC

CONTROLS

FOR

}IAINTAINING

STADILITY

153

le

27

zpich-up

cos

(9-ct)

of the

phase

hmiters

connected

in

series

with

the

contacts

rphere

I

:

current

in

the

cunent

circuit

of the

relay

tJ

:

voltage

at the

rela5;

location

Fig.

4-48.

Cliaracterjstics

of

pbase

iimiters

(1),oPeratin8.area

ot

two directtonal

imDeclance

relals

witit

difterent

internal

angles

and

6erles-connected

contac.ts;

(b)

.same,

Ior

tg'o

impedanc'e

rela1._s

s,1l[-

stra;ght_tine

-dijiriic{.-

nstics

end

a

directional

lT!_edg-nce

rele-\;

(c)

iame,

Jor tv,.o

Oiieiilo;ti1;;.;;;fi;;;;d

a

directionat

impedance

?biJii"i,;

:i;;';::.1;?ru:*j*

lli;iiers;,r

:-

ci'iiaitdrisiiii

kruk2I

cos

(r|,

*

a):

k?Iz

rT,

f

cos (q

*

a)

:

+:

consr

a

cos (g

*

a):

zpich_up

The

pick-uo

setting

is

so

sereeted

that

straight-l

ine

z

is

parallel

line

.3

and

spaced

frim

it

;;

;

airuo"L

zpi"h_rp-

Rosin

91

(4-44)

When

in

balance

or

i.e.

n'here

Ro:

arc

resistance

L/rrecf,ronal

relays

arc

far

sinrpler

than

the

impedance

son_thev

are

often

used

for

*aklij-ph;r;

"jlr;ffii.

In

discrimination.against

lo"a

Crir*ots

onli,

one phase

to

pre'ent,

misoperatio-n

of

the

protection

"l';*"ir

road

than

30

degreos.

(446)

to

straight-

(4-47)

relays.

for u-hich

rea-

limiter

i-"

acceptable

angles,

say,

of

}ess

lr\

(o)

are

of

the

main pro-

(Fig'

4-48c)

1re

use.d

as

the pha,se

limiter-q

tlie u'orkiog

"t.u-of

joint

operation

is

determined

by

the shaded

area. The

function

of

ph-ase

limiters-can'be

also

performed

b-r'

impedance

relays

traving

an

inclined

siraight-iine

characteristic.s

or

directional

releys

(Fig.

4-4Bb

and-c).

Impedance

relays

with

inclinedstraightJine

characteristics

may be

of various

types

provided

the following

conditions

are met

LCluuE

prurucrlon

nas

a tlme

delaj'

Of 1 S

2

contact

oJ

the

auxiliary

relali

Since

second

region

described

above.-

when

"'ph*se

ri*iter

te.ction-

phase,

Lhe

pL

contact

need

not'n.-r*i-r.r"a

This

adds

to

the

perfecr

op.rrtioo;f

;h;

r;;.;;A;;r.

PL

is

fitted

to

each

pro-

b-v

the

I,

(Ur)

contact.

M

o:

kllz

(4-45)

-T*-

CEAPTER

FOUR

r

-is

performed

by

a directionai

power

the power

of P

:

UI

cos

e

(U

and

/

eiay;

g

is the angle

between

the

curreni

wer-relay

ma1' be

connected

to

the

cur-

f.

Here

operation

of

the

third region

of

he

current

lags

the

same

phase voltage

lAP

I

L1!

-V4

zAft'|

12,(A?Jl

a

A

a8

ac

b."-

an.

lngle-

not greater

than

30

degree-s

or if

there

are

unbalanced

electrical

quantities'

Such

conditions

result

fr6m

short

circuits

""a

"r.-ool-p...unt

with

balanced

overloads.

The use

of

senticonductor

devices

in

reia-ving

protection

and

automatic

control

engineerif8

has

made

-it

possible

to

aulifn

a

distance

protection

star-

lirg

eiement

with

a

shaped-characreri*stic

1fig.-a_i0)r;-rr

"ili:'Jir*.ot

com_

bin-es

in

one

apparatus

a

rela-v

.x'hich

}u"rtir"1

in eonformitv

$,ith

direction

and

phase

timiiers.

It

has

a

limted

*orti"j-rrr;;""",#;;*it#'pirn..

The

use

oI

devices__resplnding.to

backrrard-seguence

components

at

a

widely

unbalan-

ced

load,

presence

oI

upper-harmoiie

eomDonenls

in c.rrrrenf and vnlrqao anrl a+ r.--^ .-^

L'

presence

oI

upper-harmonie

eomponents

iri

current

u'na oott"gl-"oa-"i'tiig.

t.u-

31"i:::l?:^il^_t!* Jfower.fysrem.

fn

recenr

vears

a.c.-singre-pn"se

eiectric

rracrion

Fig.

4-50.

ComposiLe

(shaped)

characLeristics

of

d irectidnal'im-

pedance

rela-v

r'-

cbaracteristic

of

protectel

line

T+iin

a reslgtor;9-relay

charag_

.reii

sti c

long

el-ectricai-circuits

with

inbr;iediate

trac-

occur

when

electric

locomotives

pulling

heavy

,11. i-tit

:."lltt*

o'iJilil,li,oil:;'fi:l*gi:s

io

bsck*;3r.d1esuence

compo-

(o)

wrth

pora"i,J-rJgi!!i.n_1tn'

instanta#;:i::ri;t*;;";J:

.11,'34L-ti1i

-

*'

ieJrl'

conth*

"r,jJ*ii",iiL'n-i;.it""aiir',i

il.i;;;?;""1i?:t,

*

-

hish-speed

4-52.

Connection

of

outout

ponents,

with

interpiase

.:i"i:._rlqnding

[o

bachs,ard_sequence

com_

or

rorward_seguence

vol

tage-

l""t=iig"-

circuit

manifests

itself

mainly

in

unbrani[eJ

tion

substations.

The

largest-load

viiiations

trains

start

to

move.

First

method.

Opera

ln

the

absence

of

short

circuits,

unba-lanced

loads

cause

backu,ard-seguence

components

o{

t},'*

ele*ricat

quanriries

".""prld

["n

ti,*liiG;-ilJ

;[;-;";;lr^;;.]:;;:;

l"ndesjred

starr

{-.1!:

devices

re'spoading

to

tfie

curient

or- vottage

ba-ckward-sequence

componenrs.

To

il:5t llop."t

operation

of

such

devices

u'ith

large

l"oad

current

variations,

i*u,ir"i

*ltr,oai

Dave_beeD

developed.

sequence

components

of

the

electrical

giantities

is-

pqimi-tTed-

;;iy',ip**ii.ration

of the

starting

elements

"f_ll.-

p_rotection

P;rqt-

b1;;til;

*rri"r,'iuo"rion

frbm'a

droi

in rbe

imped-

ance

or

in the

inrerphase

volrage

1or

ftrwarJ

;il;;;"j.

-ifi';;;;;1iio'Jf

such

erements

I

156

CEAHIER

FOIIR

AIIIIOM.iI,TIC

COI{IIROLS

FOR

MAECTAINING

SfAEILIty

157

of

backward-seguence

surrent

or

voltage..

This

feature

answer-q

better

the changes

in

back-

ward-sequeace

electrical

quantities

at=;h-r;iil;;r

iil

rhri,

";;;;i

;oierating

srare.

The

use

of

dsvices

'i"spon.i"e-L

the

rP6

-

tzl

V.P.

Kletskiy. At

Electrifioation

A.I

*il;t;d-tn""'d[';

s'hen

isolating

tranimi;;;ii;";;;"';;;:*

I n

the

hydroelectric

srarions

*iitrh;;;;i;ff

4@

fll#L'ii#JTfJ"tf;t,

H?1,*xx{,","if;

-

lg:

il!ii4Tiffl:?ilr1'l,"jj-.:'at

;;**,W,

Fig. 4-53. Blocking

circui't u'it,h

voltage

braking

based

on

re-IqV

IiPE-121

(auxi-

"

lian'-circuits

are

contained

v"ithin

the dashed

line)

-Fc

-

reia:- contacito

completely relDove

Yoltagc

-

braking;

-

8Q-and

oc

-

brakrng^.and

op-erati;ei;oiiJ

oioutpui

poiarizei

retay

(ro

Oc:S-,800

turns of

ggJI-0.1

wire;

,R:730

Obm;

@pn:

t,200

turns ol

rrOJI-0.l wlre;

R

-

abb

onm): DT-

ecoupling

translotraer

(ro1

:

J}]ooo

turns

ot

rrair-o.lb

wire;

u,

Alogrrt#Jriuritrtto-0.2

'wire;

taps

trom

the 135th

back*-ard-seguence

filter

(Fig.

4-55).

These harmonics

appear

in

the

primary

current and

ooltag"

duetb

tbe

influencb

oi

recrif-ving units

installed,at-the

stationary

step-down

substa-

titns-(like those iot

d.c.

electric, i""itioo,

on

electrical-

]ocomotive.s,

or

i,n workshops).

eii

uppet

harmonics filter

at th'e output bt

tne backward-segueDce

filter

adds

to

the sen-

;;; ;f ito

"-,;..

hlnelzino rlorrino ,o ir .lo.'."paqpstho rtnhalinced currents and

voltases

rnore

and

+q-e

cause

operarion

oi

iirr-r6#

lU,,)zi

ln-g }nir

I'ith

resulrqn't

nalfuncii*;i

rb.

l7o

'

',

lj:".I_

typ'

auoi";.'r.ng

;.-;ffii'r"^t.i"li:

I

i

lng

or

"Ferailon

prohibitior

J.;;*il;;;_

a

0

Fgiiog

starring

ei'ements

.ii-,nrJ..

tJir.

o"_

iill;rj"",1j-1r"ti3:'*itr.Illnes

possibie

to

Fig.

4-54.

Bra&iae

characrerisrics

of r]evic.e

isolate-suree-.-'r'it_iifi",ii;s"'"i'Ji#"l*"J3

n'*'.1-ffl'r'il1,31,:1"fffi:f.;;t'r9f,:tn-gi"'"'

switching

-operations

on

many

sectious

of

the

p_o_wer

hansmission

system.

witb

devict"lt!9-o4jngio

backward-seguence

curreats

braking

by the currenr

Ilou,insin

one

of

the phase

conductori

is

somelimes

used.

The purpose

of

this

t],pe

device

is

to

ABC

L--------

23

nc

25

lSan

(a)

connection

ot

f

l-t^

r--__J

Z

Fig.

4-55.

5th

harmonic

filrer

(")

b)

(6)

II

(

ot

v);

i+

steel

-0.35

mm

coil

forrrr

irLer

o

XBII

""P

ii

Hffi

"llff

.':il!X?:;

r.reer

vr

!4unu

CoIl:ro:1.?00turns

C

-

0.5

pF;

U,:

p00

prs'snt

th;

likelihood-or

misoperation

due-to-asymmetry,

caused

by increased

unbalanced

culrents

in

tbe

instrument

curient

transformers

during

Lsyncnronous

operation

with

a

fai-

CEAPTEN

FOIIR

AUFOMETIC

CO}flTROLS

FOR

I4AINTAINING

ST.{BLLITY

159

o"*d

.to

guickly

trausfer

the

information

s

to

the

sending

o"

,""rirri"g

""a..

oeed

remote

tripping

*yrt"*

ranges

from

rous

operg.tigl,

use

is

made

of

automatic

s

are

available.

;;J^;.:-"^:-:"o.

Lre

rrnes

rrom

the

power

receivins

svsrp.rn

.1.;.";;^;,_::^*j:

:*$rFffiI.:?ff

txl'"ilJ??t#il:1l,iiff

::":?"ty:fif*m."*,1:

speedlng.

I

4-9.

Review

euestions

Solution.

The

tripping

time

equals

60:

9,-SD.

o.7f

2,

hence

r

:

0.31

s

;

oper-atlng

in

parallel

n

tulbines

b1'bbort-time

inter_

pprng

among

the

measures

tu

:

distance

tripped

devices?

ncnronous

conditious

may

fail

allow

lor

short-time

interruptions

to

the.

6. The elenaents

revealing

the

nature

rl

po'wer

supply.

of

a

fault

may

be different

combina-

power

relays.

t+

t

,Ph

Fig.

4-56.

A.C.

circuirs

of

devicerillf;i?i*trplemented

wirh

F-c

difreren-

.

To

improTe

the

response

to i,hree-phase

short

circuits

of

a

blocking

<ievice

which

has

phase

current

braking

and

responds

to

a backvlard-s-d;;;;;

current.

ir

may

u.

*ppr.ir-.oi"j

b1'tire

start

from

a

unjt

ps-"ponding

to the

rate

ol

phase

crjr:'ei-lt

change

(Fig.

a-56;

In-s).

4-8.

Conclusions

.

l. Stable

operation

of power

s1'stems

is

feasible

providing

the-v

are

furnished

u'ith

an assemblage

of

automat,ic

devices

that

increase

the

trlnsmittiog

capacit,l,

of tie

lines,

improve

the

stabilit-r-

of

generators,

prevent,

tocatizl

and

clear

emergencies.

2.

To increase

paralle.l

operation

stabilit.l'

of slmchronous

generators,

apart

from

the use

of

automatic

excitation

controis,

the

rapid

cteaiinJof

short'cir-

cuits.,quick-unloadjng

of the

tie

lines

af d emergency^deceierati.l"

of the

gene-

ralors are

also

highl_r

important.

3'

Rapid

unloading

of the

tie

lines

is

best

accomplished

by

autonatically

"""=?;"$|F+jii."iitti'!'f:i':$.i'iJ,oo,'

circuits

considered

as

a

rneans

or

improving

tbe

trippi-ng

-the

gelerators.

at tirc

generating

sLation

(i"

fi"rii"Jrr"i

r' h.,;;;;I;;-

+-i- ^+-+.'^'^\ mL^ -----L- a r, ;

'"

'it#i}llFfi*}j*itqt1

ffi;?:r4,H'*:F.'x;ii"liilly,";',:*s.",!.*i113r..:ffr:qi

the.fault

severitl'

and

the-

prefauit

and

aftJrfault

operation.

4-

Automatic devices

allowing

the

generating

station

to

be

unloaded

w-it.hout

ire

v*iue

or

angte

6

beds,een

it;-;ili:""";;"":":;.:,^tc^-"^,..p-_tt$"ijdffi.ffifi,f:pooalo?

tripping

the generators

are

in

u:ide

use.

Classid

rnith

these

devices

are unit,s

reguiating

and

iimiting

pov'er

flows

and

devices

rapidly

deceleratlng

lrufia

unloading)

steam

turbines.

5. Unloading

the

tie

lines

by

disconnecting

the

consumers

at

the

receiving

u.

r.rescnO€

th€

€l

rt

of tbe

power

svstem

is

q!

u,Js

electrrlc

certre

s'.hen

tbe

stabifiiy;"';il;ilru?\''

(Io

rne

electrlcal

quantities

change

. ..r0.

How

is

the

maxim[d;;r;I;i;

station

T,{: tfu

sysre&

aei"rmioSS?curreDt'

in

a

transmission

line

between

a

g,enerating

i.

*l'".."'flll-ffi":";":ffi1lTt#1T'iflTr"J"X,!il'j:*,"'fli*?,1

:?T

itXSiI;;:e?

rrow

tlR

-2

tions

of

current,

voltage,

impedance

and

160

GEAPTER

FOIIR

Clzapter

F,iue

;he

blocking

devices

preventing

the

operation

.rrenr,s

and

loss

of

s5mchronism

(the

olerating

i,of

appiication

oI

devices

used

for

autonatic

.d

sections

to prevent

loss

of

synehrouismi-

secti

onal

i zing

ilevi

ces

respondin'g

to

asyn-hro_

ation

of

automatic

sectionalizing

devices

res_

rtomatic

reclosure

devices?

1

devices,

empioying

an

overfreguency

relav.

rerma

l po

wer

-

a n

d h--vdroei

ec tri

"

ii"

tiiL.i-'

*

"

AUTOMATTC

FREQUENCY

CONTROL

AP:

P,_

P,

5-1.

?urpose

and

Specific

Features

oI

Automatie

Fregueney

Control

(AF-C|_.

*

under

steady-state

cond.itions^in:

power

system

the_

power

output

of

the

generators

(Pg)

is

always

equal

to

-the

;;;;;

"i".";;

bi1t;^rJ^ai

q.a,)

r

s:

r't

(5_1)

Any

faiiure

to

meet

conditions-(i

1],

i:r;,.

io

the

case

of

a

deficiency

in

the

g-enerated

power

(due

to,

for

example,

iwjtchinE

""t

sorpe

oJ

the

generators)

or

the

excess

in

the

loY:t

lcausea

bv-g1

11ln;+s

"f"lome

loads)

*"j,

briog

abour

unbalance

between

the

power.

drrog

generated

and

consumed

(5-2)

\o-L

)

This

uubalance

affects

the

sr,eed

of

aII

the

nachines

in

the

pou,er

system

ieiai,ors

a'd

rrrofors),

it

becomes.less

q,ith

r ,.,aoorirr^ _,^l__^ -i r ^

(geneiaiors

and

urolors),

it

leco;rs

with,a

positive

value""f

i-p-.

with

a

negative

vaiue

oi

lp^o.'more

}fff"",':

Tilie

"j"|T",,:rT

til

j:"t:-::l

ji

?" :

yu

d

b,v

f re q

u e

n

c

y

a

n

d po

wer

;ifft::l;1;j"'"lr-i:',:"^:0.:^y*::

,:,...-di

i3i#',:

til.Iff;'#"l]

ifiS

t-?,:::

tt"uu::L1'j1".""[t;ll',"".:1,*'j.T:i*::l.r-r:'"il;;.[*,:;*H:ffi1":lffi

:

B_l,means

of

the

freqU.ocy

aia

i""

er^E

cruuptLvo

reg'r.llat,lon

procedure-

,,

Le

elimio"i"J'*,r,pn

+ho.o '. ^ *:'^olil .T,.ryl"tors

the

active

po.u..

deficit

rx':'::.'ii#1""1',",1;i::"'J":n:::"r:lii

::r"5;ixT#-fti".'JJ"'#'Y"Tt,1'1:

lr"ljjT:.-,'j.

li,tl^,1.^f ,XliliFrl;;ffi.#;";".".S1,::::l."i"l;:fX*,,i;j;;

:i,'.'.if:J",ililj"li,Jtt

i13'i:lf:n{ur:;#':Jffi"::jl;i:i1'S"1f,'oL'i:J;

Ierate.

ffffiJ:

is

not

avaiiable

the

resulrant

deritil

;t"#ffi"ilJ[';"ii,i"".til%.:::

\4Iith

lowered

power

deficit

aiso

rotational

decreases,

speed,

i.e.,

with

a

decreased

frequenc_v,

the

initiai

t,ltt

tlie

gut.pyt

and

power

demands

of

the

mecha_

deficit

AP

has

the

following

relationship

Ap

o/o:

Klfot,

o/o

and

the

initial

pov/er

(s-4:l

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

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