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| DSH 6598 e0 S$ `; `' O- e$ @( L/ D t
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| Problem of setting a current applied to ACB of high current rating in instantaneous tripping
2 L+ r5 `% w' P8 y | 8.3.3.1.2
+ V& _: u2 Q( I: O* x' _+ b- T | 60947-2(ed.4)- r0 s# M+ V/ l7 S9 p6 z4 h
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Standard-
. u9 F6 f' p* i+ W+ P( XIEC 60947-2 (2006-04, 4th Ed.)
' }. W6 v' f' P/ s/ q" m9 KSub clause(s):9 @* b0 m) G3 q) b5 T' I
8.3.3.1.2
8 K" U& ]9 J# [" d& ASheet:
/ a* N9 c3 Q9 ?! y, m, ~0 sDSH 659& q( _! e+ V% O6 l( E; G8 C) O
Subject:
0 b9 ^% ?+ u2 {Problem of setting a current applied to ACB of
# p$ V/ z) u0 T" X, w. |8 |" nhigh current rating for instantaneous tripping.
1 s8 W4 b4 s% b: g$ G [Key words:
# ^( L2 V- z8 I2 j4 S. rTrip limits &
) W9 g! Q. _2 _0 K9 xcharacteristics9 d( Y2 _ l f" z c* O) ]
Approved at0 f5 ~5 s) O, T) \* r5 p( }! b! z
the 45th CTL
/ A4 ^" N9 N. y6 y4 g! O! {Plenary
; W4 o3 q: W6 k2 C9 [Meeting in
" r. q8 K6 h: V' @7 TPrague in 20088 X$ X( Z/ S9 _' Y1 U2 G
Question:
: Q: ~3 n9 m3 S$ s) Q" T$ J! oAccording to 8.3.3.1.2, when the over-current opening release is a built-in part of the
`0 _. C0 ^( \2 m5 ?9 Vcircuit breaker, it shall normally be verified inside the corresponding circuit breaker.
% M" J Z/ ]1 L$ t; H' a" ^8 i6 ]For example, in case an air circuit-breaker (ACB) has a rating of 6300 A with an+ ~1 p3 ?) v: E
instantaneous trip release up to 16 In, do we have to apply 80640 A (16 In x 80 %)4 S8 C. a$ y; B+ Y4 [
and 120960 A (16 In x 120 %) to the main circuit of ACB by use of a high power
8 V5 g! g2 ^ a$ e% Wtesting facility when performing the trip test of SEQ. I?
8 t; A0 w6 P- e2 G) y3 ?1 R1 `Rationale:
) @& x" B. T c1 V# ZIt is not so easy to conduct the instantaneous trip test using the high currents6 Z2 S+ T ?: Q+ ~( f, q4 Z
mentioned above, because to do so a high power testing facility is required. In9 x5 _. c7 F; B( V2 g* F/ F
addition ACBs often have several ratings, which are determined by the specification9 S$ v' W; C+ v7 ?" |" P/ H; c1 E) n
of the CT in combination with the trip unit, and the trip unit is usually the same for all
4 g2 H# \/ w, A/ f2 nmodels.% q# W" H" {4 l: [3 H' y% I
So some accredited testing laboratories have performed this test by applying the
. }! s( |. g0 Xsecondary current of CT (normally 5 A) to the input of an overcurrent release. This( U, y& n6 ?9 L8 L. T- ]
release is connected to operating mechanism of contacts to check the mechanical# F4 O5 w2 y# n8 b
opening of an ACB. But by use of this method, we bypass possible problems such% ?7 c5 t, h: ]" ^5 j ?
as CT saturation, thermal and EMC influence on ACB, especially on single-pole
1 D% T s5 `* w- G- E/ Zconnection.7 n# w* } v4 u! @
Decision:
( ]+ `. g4 t4 L+ x2 FThe secondary current of the CT (reduced current, 5 A, for example) may be used4 ?" u; I( c2 P+ i' @9 z
for trip tests of ACBs integrated with electronic OCR for all ratings of In, but only for) c2 N- s0 B0 Z2 M( o
sub-clause 8.3.3.1.2 of SEQ I.
# e' u4 ^$ T3 T, d- o- eBut in addition, followings items shall be verified to fully cover the safety aspects of
! v' |# b/ m8 `0 kthe standard:
* y5 E+ n5 N ~& t1. The conformity of the performance (at least turn ratio and composite error)
, A6 ]7 w( X6 ]( {; fof the CT or Rogowski coil, if any, shall be verified by specifications, test/ ?" L0 P4 S) M$ O. F' s6 E; \
reports or certificates. All CTs of the circuit-breakers of the given frame8 {9 w1 o5 s5 z
size have to show the same performance characteristic.
/ {, l$ u& t j/ Z8 ^( e2. The single pole short-circuit test with a current equal to 80 % of the
5 x$ q% o% F, w; I+ Rmaximum current setting of the instantaneous release and equal to 120 %) L2 N) a( B+ z5 k3 c
of the maximum current setting of the instantaneous release shall be
( i* r+ @* f! b1 @- Wperformed at any convenient voltage with the current in the main poles of0 }# f! L& B5 N) F* [4 |
the circuit-breaker. The other tests required by the standard may be W# E7 t: w: O9 `$ g
conducted by use of a simulated input signal to the tripping unit.
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