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 * N$ s) |# c0 Y ) j6 i2 U) ^6 ?' t9 [

Short circuit and overload protection

15.2

61558-1(ed.2)

Standard(s): IEC 61558-1/2005 No. Year
, u0 L% a5 s+ I$ RDSH
0709
2008
Category: SAFE
Subclause(s): 15.2
Developed by: ETF5
. s1 Q5 f3 V# z3 ~: Y* e6 y) dOSM/LUM
% P5 q! F6 K, @2 m7 N/ N5 h& NSubject: Short circuit and
overload protection
Key words:
- Transformers
- Steady state conditions
( _, w1 G" B- }1 V- Short circuit
5 K& O0 E' D& M, TDecision approved at the
46th CTL Plenary Meeting,
" f& }& _! J/ W: p% }& cin 2009
Question:
0 ]& S  y" z/ i) }; L8 P+ X1 P8 lInherently short-circuit proof transformers shall be tested by short-circuiting the output windings until
( V$ {: P- s/ Q1 N% v; y3 Jsteady-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.
, Z# i: ~  ^/ X) ?' D4 S# xSo following questions arise:
1) Is it correct to record the temperatures after one hour when temperatures did not change (more
' y  I& R. q+ y8 jthan 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
3 t4 J! Y" c1 ]! _where safety will be impaired (the transformer bursts).
Decision:
! ?" x; ]8 ~/ u8 U# K1) Yes.
) }6 w, p: U9 Z, o2) The transformer should not be accepted.


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