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F I RST Z ONE RELAY SETT I NG
The f i r s t
zone
f o r pos i t i v e s equence i mpedance a n g l e s above 75° a n d 85 % f o r pos i t i ve
s equence i mpedance ang l e s above 7 0° .
r e f e r
to t h e local GE s a l e s o f f i ce .
3 . 78 ohms .
( a )
S e l e c t
s e l e c t e d
t h r ee ohm tap o n t h e l o n g r each r e l a y .
( b )
S e l e c t
s e t t i ng th en i s obt a i ned f rom the fo rmu l a:
NOTE:
S e e t h e
how
to obt a i n
c a l cu l a t ed i n t h i s s e c t ion .
SECOND Z ONE RELAY SETT I NG
The s e cond zone r e lay i s s e t i n t h e s ame ma nne r a s t h e f i r s t zone
r e l a y
e xcept
t h a t
s e cond
zone
u n i t
r ea c h o f 1 7 5 % i s d e s i r e d,
( a )
Se l e c t ZRl•
( b )
Re s t r a i n t S e t t i ng
MOB SETT I NG ( TYPE SLY8 1 B ONLY )
The r e a r e
t wo s e t t i ng s
o f - s t ep bloc k i ng
norma l l y be ba s e d on s y s t em load f low a nd powe r
MOB
cha r a c t e r i s t i c
c h a r a c t e r i s t i c ,
c ha r a c t e r i s t i c
t h e MOB and t h e t r i pp i ng cha r ac t e r i s t i c for the max imum t i me .
o t h e r ha nd,
the MOB s hou l d not ope r a t e on the ma x i mum load f low o v e r
t h e l i ne, o t he r w i s e t r i pp i ng o n a s ub s equent f au l t w i l l be b l oc k e d .
The
t i me r
t h a t
i s
i n s i d e
t h e
c ha r a c t e r i s t i c
f a s t e s t
s w i n g s,
GE K-49861
r e l a y can be s e t
Z R1
( ba s e
r each
t h a t
i s
l e s s
Res t r a i n t
Se t t i ng
ZR1
T
-(100%)
ZR
=
CONSTRUCTION
t h e ba s e
a
d i f f e r e n t
i s
u s ed
in
a
=
ZR
1 . 75 ( 4 . 2 )
U s e t h r e e ohm ba s e t ap .
ZR1
-(100)
ZR
to be ma k e
f u n c t ion .
Th e s e s e t t i n g s a r e
s hou l d
be
i . e . ,
s h o r t e r
t i me r,
t o pe rmi t
d e t e rm i nes
MOB
c h a r a c t e r i s t i c
s hou l d
b e
s e t
a n d
a s
long
up to 9 0 % o f
For l i ne a ng l e s lowe r t ha n 7 0°,
Hence t h e r each ZR
t ap ) .
The
than
ZR,
wh i ch,
3.0
( 1 0 %
to
1 0 0 % ) .
(100)
79%
3.78
=
=
--
s e c t ion of t h i s book f o r d e ta i l s o n
r each
t a p a n d
r each
is
r equ i r ed .
d i r e c t i ona l
compa r i son
=
7 . 35 ohms .
3
--(100)
40.8%
7.35
=
=
i n e s tabl i s h i ng
s e t
much
l a r g e r
p i c k u p
s e t t i n g
t h e
s wi ng
impedance
t h e d u r a t ion
t h a t
b u t
o u t s i d e
a s
sho r t
a s
pos s ib l e
a s
pos s i b l e
to
14
t h e
l i ne
i mpe d a n c e
=
0 . 9 ( 4 . 2 )
h i g he s t
t ap
s hou l d
i n
t h i s
c a s e,
The
r e s t r a i n t
r e s t r a i n t
s e t t i ng
A s s ume
t h a t
s ch eme
a p r ope r
i n t e r r e l a t ed a n d w i l l
s w i ng
s t ud i e s .
t h a n
t he
o n
t h e
t o
s t a y b e t w e e n
t h e
s w i ng
i mpeda n c e
t h e
t r i pp i n g
to
d e t e c t
p r e ven t
t h e
MOB
=
b e
i s
t h e
the
a nd
a
o u t
Th e
t r i pp i ng
M O B
On t h e
t h e
f rom
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