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

Short circuit and overload protection ' w& W2 B+ E- M8 H* O& @4 B

15.2

61558-1(ed.2)

Standard(s): IEC 61558-1/2005 No. Year
DSH
0709
2008
. c8 T1 P  e( _8 @; {Category: SAFE
  t, e/ U% K5 F; JSubclause(s): 15.2
" a5 F' j/ J1 Q0 vDeveloped by: ETF5
& M  O- W6 L! O# uOSM/LUM
, L" p' N8 v, {6 V7 W  g# BSubject: Short circuit and
6 A( s( i# }% ^$ {/ B& Noverload protection
Key words:
9 M; d) H* [0 i! ?# K" L- Transformers
) Q2 w) g. G( |- Steady state conditions
- Short circuit
& Z6 h1 b  u. k* u  ^2 A. _Decision approved at the
46th CTL Plenary Meeting,
( L" l2 U# x- W1 @& Xin 2009
4 E8 u7 J% e, J- Z& ?9 MQuestion:
: _3 a: N8 e. i: }% M! T$ C4 }( MInherently short-circuit proof transformers shall be tested by short-circuiting the output windings until
% V( z0 |; Y1 G  ^- [0 U3 i& gsteady-state conditions are reached.
In IEC 61558-1 “steady-state condition” is not explained. Referring to other standards the meaning of
“steady-state conditions” or “thermal stability” is that the change of temperature is less than 1°C per hour.
+ [+ Y4 c4 G1 k. y# m" A2 U% mSo following questions arise:
1) Is it correct to record the temperatures after one hour when temperatures did not change (more
than 1°C/h)?
# s; `6 w) u( `8 W1 c2) How shall an inherently short-circuit proof transformer be assessed when the above mentioned
7 W8 |6 Z. T/ Q; \+ Vrequirements are fulfilled, but it is damaged 6h after reaching the steady state condition in a way
" D! f8 D1 S. c% Pwhere safety will be impaired (the transformer bursts).
, z- j# q/ ]& F* g' I' q1 l4 RDecision:
1) Yes.
  l' m/ o$ ?5 u8 o! R2) The transformer should not be accepted.
" k# J6 q- ?# a) i) ]# `% L