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| DSH 659& r' ?5 I; I( p! O+ I
& b! F. ]: Z `, Q" z | Problem of setting a current applied to ACB of high current rating in instantaneous tripping
! X6 A+ U( C* y9 l i7 } | 8.3.3.1.2; L: U6 ]+ M: u5 a3 X2 M
| 60947-2(ed.4)
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Standard-
& j* q' i- Y+ M3 Z8 GIEC 60947-2 (2006-04, 4th Ed.)
, T9 i1 l- v" F7 b3 G0 `Sub clause(s):
4 h/ k' q% i8 {7 e8.3.3.1.2
/ `" ]+ l3 I, PSheet:! c; Z/ o! S& ]+ p
DSH 6599 q+ u3 V& M2 j
Subject:
! T \- n) | K' o+ ?$ j- d& ~3 g, vProblem of setting a current applied to ACB of
" `+ @7 ] `: ~8 A1 chigh current rating for instantaneous tripping.
$ d4 a$ o! Y& E' H( W) E1 o: EKey words:# T2 X: g8 }* F" s
Trip limits &! i# e# X+ g: i# d( i) W3 u3 ^3 W
characteristics7 ^, Z. W/ ^1 t
Approved at
5 N5 G( L) k. l m4 E9 {, u& Jthe 45th CTL, x& a" ?5 V; S0 Y( p( o0 c# M
Plenary! f: }3 J/ ^4 O- G, L( V
Meeting in
0 B3 i; G; a% q$ |! ?; a5 ~4 j( L' x' @Prague in 2008 l* _+ h& l7 E& Q. K& J6 U/ o
Question:
+ v1 m4 o5 a! m: T2 ?3 E g' @According to 8.3.3.1.2, when the over-current opening release is a built-in part of the7 @" \1 e& {8 c; j
circuit breaker, it shall normally be verified inside the corresponding circuit breaker.
' L. b$ P! r# O0 @6 s8 m7 _* xFor example, in case an air circuit-breaker (ACB) has a rating of 6300 A with an# y* @6 ~4 i( V, G) [. i- Z' Z9 ^
instantaneous trip release up to 16 In, do we have to apply 80640 A (16 In x 80 %)
+ c6 d$ S2 x+ f) {and 120960 A (16 In x 120 %) to the main circuit of ACB by use of a high power" a) h& V1 W6 A1 u' q
testing facility when performing the trip test of SEQ. I?- ^, E3 D8 K4 b G' f
Rationale:
2 c! q. v s& @8 tIt is not so easy to conduct the instantaneous trip test using the high currents# [$ H' E0 m5 x
mentioned above, because to do so a high power testing facility is required. In
8 M B8 ^) n( ]! W. Faddition ACBs often have several ratings, which are determined by the specification) s ]; T$ [, w+ }8 Z' p8 t' ]
of the CT in combination with the trip unit, and the trip unit is usually the same for all
# \7 O; v1 |/ vmodels.7 f: x. a" ~3 N1 A) r
So some accredited testing laboratories have performed this test by applying the; j* k) Q/ x% w; z% t* m2 _8 H" _. }1 g6 K
secondary current of CT (normally 5 A) to the input of an overcurrent release. This
, z9 I' \) h6 w2 P. h8 K0 o# Trelease is connected to operating mechanism of contacts to check the mechanical
% ?) }, Q$ r% R2 }opening of an ACB. But by use of this method, we bypass possible problems such$ N/ F2 h. H$ o2 m! y/ t
as CT saturation, thermal and EMC influence on ACB, especially on single-pole, A: b9 B3 L6 E0 R2 ~
connection.7 R0 i" O, \& j: S
Decision:
: p, C1 V% c* Q/ z4 A0 D, T SThe secondary current of the CT (reduced current, 5 A, for example) may be used
# i1 c2 V- G* X6 L' Sfor trip tests of ACBs integrated with electronic OCR for all ratings of In, but only for
' z' E( l8 N9 j6 ysub-clause 8.3.3.1.2 of SEQ I.
9 \, c9 l2 z/ gBut in addition, followings items shall be verified to fully cover the safety aspects of
: c+ O- N, R) s" y7 lthe standard:. r5 b4 f8 }" U% g
1. The conformity of the performance (at least turn ratio and composite error)/ w9 a8 X1 ?/ m( ]: v( N1 C2 U
of the CT or Rogowski coil, if any, shall be verified by specifications, test# R- c6 o$ O9 \" `
reports or certificates. All CTs of the circuit-breakers of the given frame
" `0 H* I V1 R( Qsize have to show the same performance characteristic.
% A0 q3 f3 u# X( a' l. G5 a9 c2. The single pole short-circuit test with a current equal to 80 % of the
4 c _9 t# c t1 Wmaximum current setting of the instantaneous release and equal to 120 %8 e* h: G) V# ~" g
of the maximum current setting of the instantaneous release shall be
0 B8 v5 W1 Z% y d, s- eperformed at any convenient voltage with the current in the main poles of
+ Y4 L3 Y) r5 V% F a9 p- Mthe circuit-breaker. The other tests required by the standard may be# h; m+ f- o% d, e
conducted by use of a simulated input signal to the tripping unit." g3 B* z V m2 e
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