I ·
f
•
I·
I .
;
-
S E CT I ON
STAT I C OVERC URRENT TR I P DEV I CE
A .
I NTRODUCT I ON
The A l l i s -Cha l me r s S ta t i c Ove r c u r r e n t T r i p Dev i ces e re
��np l e t e l y
s t a t i c ; t h a t i s t h e r e a re no mov i ng pa r t s o r con t a c t s .
The
c i r c u i ts of the dev i ce a re des i gned for l i gh t l oa d i ng of componen t s and a re
t empe ra t u re compen s a ted f o r accu r a cy a nd s t a b i l i t y of ca l i b ra t i on ove r w i de
t empe r a t u re r a n ges f o r i nd ef i n i t e pe r i. od s of t i me . The s ta t i c ove r cu r re n t
t r i p dev i ce s , wh i ch rep l ace t he e l e� t ro-mech a n i ca l s e r i es ove r cu r r e n t t r i p
de v i ces , pe r f o rm t h e s ame f u nc t i on w i th a h i ghe r deg ree o f a c c u racy
a
nd
ve rs a t i l i ty .
I n common w i t h s e r i es ove r c u r ren t t r i p dev i ces , a l l
ene rgy
for ope ra t i on
i s
ob ta i ned f rom ov e r l oad o r f a u l t c u r ren t . N o
ba t t e r i es
o r
o t h� r ex te rna l
power
s o u rces
are
requ i red .
The comp l e t e s t a t i c ove rcu r re n t t r i p s y s t em cons i s t s
of
t h ree cu r re n t t ra n s
forme r s , one pe r phas e , moun ted on t h e c i rc u i t b reake r p r i ma ry connec t o r s ,
a
re l eas e magne t , a n d the s t a t i c ove r c u r re n t t r i p dev i ce . Th i s s y s t em
ope ra tes t o t r i p t h e c i r cu i t b reake r when a s ys t em o ve r l oa d cond i t i on exceeds
a p re- s e l ec t ed va l ue of c u r r en t .
T r i pp i ng w i l l occ u r
a f t e r
a p r e d e t e r m i ned
t i me de l ay o r i ns t a n t a neous l y depend i ng upon t h e adj us tmen t s e l ec ted and t he
magn i t u d e of t he ove r l oad .
The s t a t i c t r i p d e v i ce con t a i ns t h ree cu r re n t t ra n s f o rme r s wh i ch p rov i d e
a
�ma l l
l ow
v o l t a ge s econda ry c u r ren t p ropo r t i ona l t o t h e c i rc u i t
b r eake r
pr i ma ry
c u r ren t .
T h e s econd a ry of each t ra n s fo rm e r
i s
conne c t e d i n
s e r i es
w i t h
a
powe r s u pp l y t rans f o rmer a n d an a ux i l i a ry t ra n s forme r . Th e o u t p u t
o f t he powe r s u pp l y t ra n s f o rme r s i s rec t i f i ed t o p rov i de D . C . ene r g y t o t h e
r e l ea s e magne t t r i p co i
I a
nd a l s o
a
regu l a t ed D . C . powe r s upp l y t o ope ra t e
t ra n s i s t o r c i rc u i t s .
Poten t i ome t e r s
or rheos t a t s
con nec ted i n
pa ra l l e l w i t h
t h e a ux i l i a ry t ra ns f o rmers p rov i d e a n A . C . s i gna l vo l t a g e p r opo r t i ona l
t o
t he
p r
i
m
a
r
y
c u r ren t .
Th i s
ac t s a s t h e
i n t e l l i ge n ce I np u t fo r t he
device �
and t h e m a gn i t u de o f t h i s A. C . v o l t a ge d e t e rm i nes whe t he r o r not t h e
b r ea ke r
w i
1 1
t r i p and t he t i me de l a y b e f o r e t r i pp i ng . The re l a t i on be tween t h i s A . C .
s i gna l vo l t a ge a n d t h e p r i ma ry c u r ren t can b e va r i ed b y adj u s t i n g
t he
po t e n t i ome t e r s
to s
e
t
t he m i n i mum p r i ma ry c u r re n t a t wh i ch t r i pp i n g
w i I I
occu r .
Th i s i s
t h e p i ck -up adj us tmen t .
A
t ra n s i s to r t r i g g e r c i r cu i t preven t s ope r a t i on of t h e t i m i n g c i rcu i t un l es s
t he s i gna l exceed s 95% of p i ck-up v a l u e .
I f t h e t r i g g e r has o pe ra t e d , a
capac i t o r w i l l c h a rge g r a d ua l l y t o a vo l t a g e wh i c h causes t h e s ta t i c s w i tch
t o ope r a t e . e n e rg i ze· t h e
t r i p co l I , and
t r i p t h e b r eake r .
I f a t a n y t i me
be f o r e the s t a t i c s w i tch a c t ua l l y
ope r a tes ,
t h e p r i ma ry c u r r e n t
d
e
c
reas
es to
95%
o r l e s s of t h e
s e t
p i c k - u p , t h e t r i gge r w i
I I
t u rn of f a n d res e t w i
I I
t a ke
p l ace .
S ome m i nor va r i a t i on s I n p i ck-up a n d t i me de l ay may b e expec t e d w i t h tempe ra t u r e
f l u c t ua t i o n s f r�n a n amb i en t
o f
-40°C . t o a n amb i en t o f 5 5°C .
A
ty p i ca l b re a ke r r a t i n g p l a t e i s s hown i n F i g u r e 7A .
The max i mum r a ted
ampe res
i s
d e t e rm i ned
by
t he
c u r ren t t rans f o rm e r s mou n t ed on the c i rcu i t
b re a ke r p r i ma r y c on ne c t o r s .
Th e max i mum cu r ren t a va i l a b l e
I s
l i m i t e d by t h e
c i rcu i t b rea ke r f rame s i ze . S i nce
the
s t a t i c ove r c u r ren t t r i p dev i c e
compor)f>" ts
a r e ca l i b ra t e d i n te rms of t ra n s f o rme r s ec o n d a r y c u r r en t , t he s ame d ev i ce
c
�
u s e d w i t h any of t h e g r o ups
of
c u r r en t t r a n s f o rme r s ava i l a b l e .
-
I I -
Summary of Contents for LA-1600
Page 6: ...AALLIS CHALMERS _ Wl IGTi 4 1 1 r 1 I i C I I li r L _ I ll l ...
Page 18: ... ...
Page 20: ......
Page 22: ......
Page 24: ......
Page 26: ...t I 1 1 f I a4 r A ALLIS CHALMERS I I T r I I ...
Page 30: ......
Page 32: ......
Page 38: ......
Page 40: ......
Page 46: ......
Page 48: ......
Page 50: ... ...
Page 56: ......
Page 90: ...AALLIS Ci IALMERS F I G 7 0 ...
Page 91: ... AALLIS CHALM ERS F I G 7 E 11 o _ _ ...
Page 99: ... ...