DSH 709/06 Short circuit and overload protection

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DSH 709/06 6 v* J$ |: }# B. h9 n5 R/ M

Short circuit and overload protection 2 O) }' u% o8 x2 k! i; y

15.2 ! N; C" M5 Y9 e5 W# b6 B' @5 x

61558-1(ed.2)

Standard(s): IEC 61558-1/2005 No. Year
DSH
0709
2008
4 |1 z+ U0 B4 F' }Category: SAFE
Subclause(s): 15.2
Developed by: ETF5
OSM/LUM
: i! z- y, W' j" n0 ^: RSubject: Short circuit and
& y. h9 s# @5 K+ K' koverload protection
3 w* X: g- Y( ~7 h# JKey words:
5 S) }0 `) q; x+ H- Transformers
% R( j, L" ^5 `+ j' J" u, T5 r- Steady state conditions
5 [! x6 [# q7 Z0 d+ }: {- Short circuit
" z4 g% ?$ B/ UDecision approved at the
+ C2 E5 E5 R% H4 t. D46th CTL Plenary Meeting,
# D% v' ?  O1 M4 z% t" cin 2009
& S4 V, ?/ T% T0 @* X2 ?' J) }' h" L- xQuestion:
Inherently short-circuit proof transformers shall be tested by short-circuiting the output windings until
steady-state conditions are reached.
% _( n) H$ X+ @  h, e! f$ s5 bIn IEC 61558-1 “steady-state condition” is not explained. Referring to other standards the meaning of
* h& U7 c0 x% I0 d8 w“steady-state conditions” or “thermal stability” is that the change of temperature is less than 1°C per hour.
So following questions arise:
" p0 H, k" G8 q6 G3 I5 o' |: O: b1) Is it correct to record the temperatures after one hour when temperatures did not change (more
6 F& i/ S+ w" ]/ v) q2 lthan 1°C/h)?
( Q7 K6 H3 Y; v& a+ _- r2) 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
# l9 B1 `+ I5 Z3 |- `where safety will be impaired (the transformer bursts).
Decision:
. b& V# f! r+ E( \9 _9 y7 B1) Yes.
6 Z! ^7 i9 x8 H# O  e% w) z2) The transformer should not be accepted.

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