Allis-Chalmers BWX-6637-5, Инструкция

Страница: 45 / 88

Mo d e l s
AG ,
DG.
The m i d d l e knob on
the
r i gh t hand s i de
of
t he
Mode l s AG ,
OG ,
I
s used to
s e l ec t
the s
e
n s i t
i
v i t y
o.f g r ound
c u r r e n t
d e t ec t i on . I t
i s ca l i b ra t ed as a p e r c e n t a ge of t he M I N I MUM ava i t a b l e p i ck-up c u r r e n t
s h own
on t he b rea ke r
r a t i n g
p
l
a
t
e
( F i g u re 7A) . I t does n o t have a ny
r e l a t i ons h i p to t h e p i c k- u p c u r ren t s e l ec t ed for t he phase
s
e t t i n g
s
.
Ca l i b ra t i ons a re ma rked a t
20 ,
40 , 60 , 80%
b u t adj us tme n t i s
con t i n uous .
EXAMP LE : 1 . A c i r c u i t b r eake r has
a
r a t i ng p l a t e p e r
F
i
g
u re
]A.
T h e p i ck-up s e t t i ngs a r e o n " C " to
s e l ec t 300 A m
p s
p i c k- u p . The g round
p i
c
k
-
up
I s
s e t a t
40% .
The g round c u r r en t t h a t w l 1 1 c a u s e t
r
i
p
p
i n
g I s t
h
e
r
e
­
fore not l es s than 40% o
f
200 Amps , o r 80 Amps .
EXAH? l.E : 2 . Same cond i t i ons exce p t p i c k-up
s e t t i ngs a r e
on 1 1E 1 1 to
s
e
l
e c
t
40 0
Amps p i c k- u p .
T h e g r ound c u r r e n t p i c k- u p
I s s t l
1 1 80 Amps , based on
the
m i n i mum ava l ! a b l e p i ck-up of
200
Amps .
G round
c
u rre
n t
p i ck- u p i s t r
ea t ed I n t h e s ame man n e r a s pha s e c u r ren t
p i c k-up when u s i ng t h e c u r r� n t - t i me curve , and t h e s ame c u rve
( F i g u res
70
and 7B)
i s used for
d
e f
i
n
i
n
g
t i me
de
l a y
.
3 . B rea ke r ra t i ng pe r F i g u re'/7A. Phase p i ck-up s e t t i n g
"E"
(400 Amps ) .
G ro un d
p i c k-up
s
e
t
t i n
g 40% (80 Amps ) .
An
a c t ua l
g round c u r ren t of
320 Amps
i s f l ow i ng .
320
Amp
s
g round cu r re n t
i s
fou r t i mes (4X) p i c k - u p a nd
w i l l c a u s e a t r i p ope r a t i on I n
f
ou
r and one-ha l f s e c onds
(
on the m i n i mum
t
i
m
e band
)
as shown on t h e cu r r en t - t i me
cu rve ( F i g u r e 7E) . Howeve r , th i s g round c u r ren t i s
muc h
l es s t h a n t h e pha s e p i c k - u p s e t t i n g , and wou l d n o t
b e
recogn i zed
on the phas e
p i ck- ups .
The l owe r
l
i
m
i t of g round fa u l t recogn i t i on on t h e Hod e l s AG , OG , s ta t i c
t r i p dev i ces
i s
40 Amps g round cu r ren t . P r i ma ry cu r re n t t ra n s f orme rs
t h a t p rov i de a M I N I MUM CONT I N UOUS CURRENT SETT I NG
OF
L E
S
S THAN
200 AMPS
( G r
o u p
IV ,
F
i g
u r e 7A) s hou l d not be used
f o r
g round fa u l t d e t ec t i on .
Mode l s A I and AG . T h e knob on t
h
e l aw-�e r l e f t s e
l
ec
t s
a
Clu· re n t v a l u e
a bove w
h i
c
h t r i pp i n g
t akes
p
l a c e
I ns t a n t a neous l y I ns t ead of on t i me
d e l ay .
The
c
a
l
i
b
r
a
t i o
n
i s ma r ked
i n
mu
l
t i
p l
e
s
of p i ck-up
and
a
l
l
ows
s e l e c t i on
be tween
f i ve t i mes ( S X ) and
f i f t een
t f mes ( 1 5X) p i c k - u p . I t
I s
t h us
d
e p e nde n t on the s e t t i ngs s elected for pha s e p i c k - u p ( a s we l l a s
g round
p i c k - u p on the Mode l AG) . The cu r ren t - t
i rne
c u rve
( F i g u re 7E) s h OYJS how
t he
t i me de l ay w i l l
f
o l l
ow
the approp r i a t e t i me b a n d c u rve u n t l
I
t h e
i n s t an t a neous s e t t i n g i s reached , then w i 1 1 go
t o
t he i ns t an t a neous v a l ue
f o r a t I c u r re n t s
above t h a t s e t t i ng .
- 1 4 -
(