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paths are :
F i r s t z o ne - D and Z l ;
D ,
Z2 and T2 ;
Third z one - D,
rier c ontro l le d tr ipping path
and RRP c ontac t s .
For ground prot e c t i on a c ar
rier c ontr o l led trip c ir c u i t
the c ontac t s Do and Io2 of the
the c arrier c on t r o l l e d c ontac t ,
tac t I o 3 i s used to s t ar t c ar r i er .
RRP and RRG ,
are o n the b lo c kinL r e lay
led
by t he c arrier s ignal o p erat ing RRH and RRT
c o i l s .
The c ont ac t s
the
l e f t
part
of the f i gure s erve to s t ar t the
transmi s s i on
o f c ar r i er
c ontact I o 3 perf'orms
the s BJne func t i on
ground f au lt s .
The ground s t art c on t ac t ,
i s o p er a t e d
by an over- c urrent e l ement s e parate
from that whi c h operat e s the tripping c ont ac t .
C arr i er i s s t ar t e d
of the c arrier
s t ar t c ontac t s
c arrier t e s t push b u t t o n ,
r i er s t ar t c ont ac t s .
The s e c ont ac t s c onne c t the
p la t e of the c ar r i er o s c i l lator tube t o p o s i t ive .
The ·c athode of the o s c i l l at or tube
to negat ive
through th� b ack c ont ac t s
C SG as
shown
in F igure
c ontro l le d
by the tripp ing c ontac t s ,
f o r pha s e fau l t s
and Do and
faul t s .
When f au l t power f lows
t e c t e d line s e c t i on ,
t h e
and Z2 c lo s e
f o r phas e fault s
c o i l of the auxi l iary c o ntac t o r s w i t c h ,
b e energ i z ed .
T h i s c au s e s the back C SP c ont :_- c t
i n t he c arr i er c on t r o l c ir c ui t s
s t o p s c arr i er
b y rai s ing
above the o p erat ing value ,
operat inz c o i l of the r e c eiver r e l ay to be ener
g i z e d by the s t at io n batt ery .
Simi larly ,
f or cround faul t s
I o 2 olo s e t o energi z e
i l i ary c ontac t o r swi t c h ,
t ac t ,
C SG ,
s t op s c arrier
t ing c o i l o f , the r e c e iver r e l ay t o be energ i z e d .
The arran::;ement
and s t o p c ir c ui t s ' i s such that opening ' C SP
C SG c ontac t s s t op c arr i er r e gard le s s of how c ar
r i er is
s t art e d .
Thus r e l aying
at a l l t im e s over all o ther u s e s
c hanne l .
The c ir c u i t s are arranged
of
ac t i on
the ground re lay
r e lay s .
enc e
over the phas e
c onne c t ing the c ontac t s C SO
HRP r e l ay
around CSP c arrier
shown .
Thi s means that if Io3 of the £:r o und re
lay s t ar t s c ar r i er ,
i t i s then
the C SP c 0ntac t
and the pha s e
c arrier .
T h e purp o s e
i s to prevent p o s s ib l e inc orr e c t
the pha s e r e l ay s
due to l o ad current s
f l ow of p o s it i ve and negat i ve s e quenc e
during external g r o und faul t s .
The c ar r i er c ont ro lled
i s a s e n s i t ive
po lar i z e d
with two make c ontac t s ,
breal( c ontac t , RRB .
The s e c o ntac t s ar e operated
by the ac t i on
of two c o i l s ,
c o i l ,
RRT ,
ener g i z e d
c ontr o lled
as explained
c ontac t s ,
and the o ther a c arr ier h o ld ing c o i l ,
RRH,
c onnec t e d
i n the p l a t e c ir c ui t o f the c ar
r i er r e c e i v ing t ub e .
de- energ i z ed and the make c ont ac t s ,
are hell! open by a magne t i c b ia s .
prevented
from operat ing when the c arrier ho ld
ing c o i l ,
RRH,
is energi zed
operat ing c o i l , RRT ,
is energ i z e d .
that as long as c ar r i er is b e ing r e c e ived e i t her
from
the loc a l transmit t er or
Sec oYJd z one -
and TJ .
The c ar
i s through D,
i,s
set up
throu;�h
ground r e l ay and
RRG .
The c on
The c ontac t s ,
c ontro l
&
Z3
( A,
B ,
C phas e s )
for
pha s e faul t s
and
for the
Io3 ,
by c lo s ing any one
Z3 or
I o 3 ,
the
or the auxi l i ary c ar
i s c onne c t ed
C SP
and
1 .
C arrier s t o pp ing i s
D and Z2 ,
Ic2
f o r
ground
into the
pro
t r i p p ing
c on t ac t s , D
and
permit
the
C SP , , t o
t o open,
whi c h
t h e c athode
v o ltage
and perm i t s
the RRT
Do
and
the c o i l
of ano ther aux
C SG ,
who s e
back c on
and perm i t s the opera
of the c arrier
s t ar t
and
has pr eferenc e
of the c arrier
so that the
c an b e � iven pr efer
Thi s
i s
done
of the type HRK
s t c· p c c,ntac t s
impo s s ible
for
r e l ay s
t o
s t o p
of thi s gro und preferenc e
ind i c at i ons of
and.
the
current s
r e c e iver r e l �y
d- e
r e lay
provided
RRP
and
RRG,
and one
one
an
operat ing
by the l o c al
b at t ery and
ab o v e
by C SP
and C SG
Norma l ly ,
b o t h c o i l s ar e
RRP and RRG,
The r e lay i s
even
though
the
This
means
from the oppo s i t e
POS.
Z2
in
RECEIVER RELAY- COILS RRH �OlDING )&RRTCffi i PPIN<i};CONTACTS RRG,RRP, RRB
Simp l i f i e d D- C Sc hemat i c
C ir c u i t s Us ing the Type HZ Relay
One -Br e ak Third Impedanc e E lement C ont ac t s ,
e n d ,
n
rgi
RRH i s
e
e
pre v e n t e d .
The c omp l e t e
be brief ly surnrnar � z ed as f o i lows :
terna l phase- t o - phase f au l t j u s t beyond the zone
of one of the Zl e l ement s .
i t iated irrunediat e ly
the c lo sure
of one
whi l e ,
the d ir e c t i onal and s e c ond zone impedanc e
by
c ontac t s c l o s e and ener g i z e the aux i l i ary swi t c h ,
or
C S P ,
s t o pping
c arrier and
as
at inG c o i l ,
RRT ,
Sinc e t he S BJne ac t i on
end of the line ,
c on t ac t , RRP ,
i s c l o s ed
the t r i p c irc u:i_ t s
the trip c o i l
at one end has already b e en ener
g i ::; e d throuch Z l .
nal tc the s e c t i on ,
o c c urred s ine �
the c ar r i er
would have b e en ener g i z ed
end near e s t the f au l t where D would no t b e
ed to
s t op c arrier .
If
an
f ault is as sumed,
t a c t I o 3 ,
and one
c l o s e t o s t art c arrier .
enc e
c ontac t is c onne c t ed ,
I o 3 .wi l l energi z e C SO and its c ont ac t will
out C SP thus makinc it
r e l ay s
t o s t o p c ar r i er .
t r ipp ing c ontac t s Do and
g i z ing the C SG aux i l i ary r e lay to s t op c arr i e r .
I t
w il l b e n o t ed
s t ar t e d
at either end
erat e s
a s t art ing
- 3 -
CAR R I ER CONTROL
OR
ALARM, TELEMETERING
RELAY
SUPERII I SORY RECEIVING
F igure 2
of the C ar r i er C on t r o l
With T w o Make
and c a r r ie r
z
d
t r ipping
e
s e quenc e
of event s
As sume an ln
C arr ier wi l l b e in
at b o t h e nd s of the line by
of the Z3 c ontac t s .
energi z ing t h e o p er
of the c arri er' r e c e iver r e l ay .
has oc curred
at the
no c arrier is r e �e ived anq the
at both ends c omp l e t ing
through D and
Z2 ,
However,
If the f au l t had b e en e xt er
then tripping c ould not have
holding
c o i l , RRH,
by c arrier
from
internal
two - ph a s e- t o - ground
the
ground
, c arr i er
s t art c on
c ontac t s
of t he phas e
If t he
ground prefer
then
the operat ion of
impo s s ib l e
for
the
However,
the
I o 2 ,
will c lo s e
that c arrier
unl e s s fault current o �
e l ement
( f ault
N EG,
i s
may
M ean
f ar
the
c lo s
w ill
shor t
phase
ground
ener
not
i s
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