DSH 709/06 Short circuit and overload protection

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广东安规检测
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DSH 709/06 - ^5 `. M* c5 l$ R9 j

Short circuit and overload protection 4 L0 C, ~; v  C% `) p* @0 U

15.2

61558-1(ed.2)

Standard(s): IEC 61558-1/2005 No. Year
: J$ w* p, F' B9 FDSH
; g7 g- \3 ^' N; Q' Z0 G2 f9 Z0709
- O- O8 C) `% a0 O# X" D) k4 \2008
Category: SAFE
8 x: ~8 y2 h7 l6 X: I9 f( HSubclause(s): 15.2
Developed by: ETF5
# z: C: _0 \  nOSM/LUM
Subject: Short circuit and
) p9 T" b7 I: o2 N3 n! Hoverload protection
7 K5 D5 h0 x; W; Y" rKey words:
  x, }& R/ S* V! Y- Transformers
- Steady state conditions
$ s- l) d  Z  G# r9 Q- Short circuit
Decision approved at the
% A  y# J! f. V& v" w$ |+ O46th CTL Plenary Meeting,
( f" K3 k& u0 s. X/ _( Uin 2009
Question:
3 i$ H7 J' z" W4 zInherently short-circuit proof transformers shall be tested by short-circuiting the output windings until
steady-state conditions are reached.
In IEC 61558-1 “steady-state condition” is not explained. Referring to other standards the meaning of
: r: h/ v5 J8 f1 M3 }- |, Z+ Z“steady-state conditions” or “thermal stability” is that the change of temperature is less than 1°C per hour.
So following questions arise:
% T( |( c9 b# v1) Is it correct to record the temperatures after one hour when temperatures did not change (more
than 1°C/h)?
2) How shall an inherently short-circuit proof transformer be assessed when the above mentioned
requirements are fulfilled, but it is damaged 6h after reaching the steady state condition in a way
6 _; W% |, S) q( Uwhere safety will be impaired (the transformer bursts).
, F* a7 F4 G# p( f7 }Decision:
1) Yes.
2) The transformer should not be accepted.
& \! U/ V& }& N! h
& \7 ]$ c3 r' |& \
6 o  J$ {1 S* ^+ R) j