DSH 659 Problem of setting a current applied to ACB of high current rating in in

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DSH 659 " w# X, z  S- y3 D8 G! m $ r7 L6 h2 T9 j( `+ Q, S7 ~. A

Problem of setting a current applied to ACB of high current rating in instantaneous tripping

8.3.3.1.2 : o, J5 q4 H- d8 s% i7 Y8 {

60947-2(ed.4)

+ }' q6 }# r9 g+ V0 J2 _' ~Standard-
IEC 60947-2 (2006-04, 4th Ed.)
$ [% j2 i7 C' f. M& |Sub clause(s):
8.3.3.1.2
# W: y: u, u4 c) j8 c" VSheet:
, H; G  M! ?6 @DSH 659
, z7 l3 c  O2 X4 H7 s) p9 m- ESubject:
5 I7 r3 N" s+ H1 V+ D7 n% `" E9 uProblem of setting a current applied to ACB of
( F+ {- K/ J: M) _$ M! ]* V8 uhigh current rating for instantaneous tripping.
1 O: _; y; Y5 j. B) K3 f  a. OKey words:
Trip limits &
3 n. s" ]: b% p2 z3 Kcharacteristics
Approved at
) P1 v+ b5 I+ ]7 ethe 45th CTL
% I- P7 V/ N& R- X, V; q( g. dPlenary
Meeting in
Prague in 2008
Question:
( d" Z1 T, }5 I" w: l1 {- f5 oAccording to 8.3.3.1.2, when the over-current opening release is a built-in part of the
, B- Z  U0 G  u4 R- t7 T/ scircuit breaker, it shall normally be verified inside the corresponding circuit breaker.
$ r! q; J: l- d/ |7 T! b" _For example, in case an air circuit-breaker (ACB) has a rating of 6300 A with an
instantaneous trip release up to 16 In, do we have to apply 80640 A (16 In x 80 %)
and 120960 A (16 In x 120 %) to the main circuit of ACB by use of a high power
2 c+ {: T! N3 Y1 Ltesting facility when performing the trip test of SEQ. I?
Rationale:
- s7 w' p0 J+ V2 B! zIt is not so easy to conduct the instantaneous trip test using the high currents
mentioned above, because to do so a high power testing facility is required. In
4 p' B5 L) O. [% {) uaddition ACBs often have several ratings, which are determined by the specification
of the CT in combination with the trip unit, and the trip unit is usually the same for all
models.
So some accredited testing laboratories have performed this test by applying the
1 N# I; D' f% G4 p: S- esecondary current of CT (normally 5 A) to the input of an overcurrent release. This
/ o. u( F6 v4 Hrelease is connected to operating mechanism of contacts to check the mechanical
- Z( d# ]7 S1 c7 q- y2 A7 }" ~( {opening of an ACB. But by use of this method, we bypass possible problems such
as CT saturation, thermal and EMC influence on ACB, especially on single-pole
6 C4 e* l9 m8 {) Q9 p5 D' A+ jconnection.
& Z$ q' q, }/ f/ B) z, ]! SDecision:
& z( \- ^3 ?- `, |+ Q% [The secondary current of the CT (reduced current, 5 A, for example) may be used
for trip tests of ACBs integrated with electronic OCR for all ratings of In, but only for
8 \& ^( U1 N, R# }sub-clause 8.3.3.1.2 of SEQ I.
But in addition, followings items shall be verified to fully cover the safety aspects of
. R1 B2 `1 f* Q7 Wthe standard:
6 z  F$ z1 Y7 u9 |7 Y1. The conformity of the performance (at least turn ratio and composite error)
5 ?& B9 F" J/ y4 S+ b" @of the CT or Rogowski coil, if any, shall be verified by specifications, test
reports or certificates. All CTs of the circuit-breakers of the given frame
size have to show the same performance characteristic.
2. The single pole short-circuit test with a current equal to 80 % of the
maximum current setting of the instantaneous release and equal to 120 %
of the maximum current setting of the instantaneous release shall be
performed at any convenient voltage with the current in the main poles of
the circuit-breaker. The other tests required by the standard may be
conducted by use of a simulated input signal to the tripping unit.

6 C" h% \( D) n" ?* `