DSH 709/06 Short circuit and overload protection

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DSH 709/06

Short circuit and overload protection 5 s- O5 a  w2 h6 ]9 o; H

15.2

61558-1(ed.2) 0 `2 {+ S8 S6 q2 E& j; }

- Z% h. N: h+ x1 h& q2 @4 YStandard(s): IEC 61558-1/2005 No. Year
DSH
0709
+ y0 h: R4 d  K  w$ c2008
Category: SAFE
Subclause(s): 15.2
Developed by: ETF5
OSM/LUM
5 l4 ]# X# q) |' o' l: z* F5 o: g$ aSubject: Short circuit and
5 t! U* D; |  Q6 k- Joverload protection
Key words:
1 O/ A$ [, C: A+ G8 q- Transformers
% x4 e) q  T; j2 Q- Steady state conditions
. m! E+ P: D; \4 [( v$ [0 b- Short circuit
Decision approved at the
46th CTL Plenary Meeting,
in 2009
' @5 z' V) W; C. x4 Z! I9 cQuestion:
Inherently short-circuit proof transformers shall be tested by short-circuiting the output windings until
' h$ x3 N3 o4 E% Asteady-state conditions are reached.
% v% J0 @7 A1 Z, }7 ^: D; [1 y0 `+ YIn IEC 61558-1 “steady-state condition” is not explained. Referring to other standards the meaning of
$ d" k. I5 Z- \4 ]1 {“steady-state conditions” or “thermal stability” is that the change of temperature is less than 1°C per hour.
So following questions arise:
1) 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
where safety will be impaired (the transformer bursts).
Decision:
1) Yes.
& Q& O  o* t( k: l0 \, n  w8 [2) The transformer should not be accepted.

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