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 2 C: D0 Q: L# I* x7 X  M, U

Short circuit and overload protection

15.2

61558-1(ed.2)

8 G9 c" X. U. h& q$ c& DStandard(s): IEC 61558-1/2005 No. Year
DSH
) C, t! o- [7 S5 Q8 D' Z$ ~7 C/ z0709
9 H. h# @: g) u% K" h7 ~- E2008
! }0 V$ i* s* d6 s1 L2 O# wCategory: SAFE
Subclause(s): 15.2
3 V% Z7 a8 E: a" }4 h) Y: dDeveloped by: ETF5
7 m9 F& O; Q' |& p: QOSM/LUM
Subject: Short circuit and
overload protection
7 L: z1 Z4 _/ I; V7 b  aKey words:
- Transformers
9 h$ h( a( E$ W% V- I# E- Steady state conditions
2 x6 P8 C' h: L5 u- Short circuit
Decision approved at the
. g5 D0 W2 _, [0 S7 i: _8 I46th CTL Plenary Meeting,
in 2009
: ^3 z  ~; D/ j  i; Y" K1 wQuestion:
Inherently 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
“steady-state conditions” or “thermal stability” is that the change of temperature is less than 1°C per hour.
So following questions arise:
. k- @& C. v% {  V* d% t1) Is it correct to record the temperatures after one hour when temperatures did not change (more
than 1°C/h)?
, B7 x4 y- Y8 H( b/ j2) How shall an inherently short-circuit proof transformer be assessed when the above mentioned
4 j2 r% Q- }/ f4 Y# ]requirements are fulfilled, but it is damaged 6h after reaching the steady state condition in a way
5 I4 f. I9 H6 B5 S! s- q( ]where safety will be impaired (the transformer bursts).
* y/ N6 W5 T# d( N9 tDecision:
1) Yes.
0 Z, R8 A% j; E6 }& Y2) The transformer should not be accepted.

4 T' S5 c: t1 D/ B8 }
% m/ T! V. }( s: W