PDSH 1021 Short circuit and overload protection

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PDSH 1021 2 v& S8 H& k# {$ j8 U3 E5 |# B# H / W7 g) l7 {+ ~9 Z

Short circuit and overload protection

15.2 1 u$ s" @( D8 c, f: s# u* j, [: d

61558-1(ed.1);am1 & 61558-1(ed.2);am1

Standard(s):
IEC 61558-1
All editions
Subclause(s):
1 p% m9 w7 z4 H( k9 C15.2
No. Year
! a, o5 k5 p5 D: k: JPDSH
; L6 N7 J+ j1 J! L# q( P' ], P1021 2010
Category: SAFE Developed by: ETF5
OSM/LUM
% a* [7 J# o8 ^8 F6 mSubject:
1 P3 s$ \  U$ i+ a+ O9 a, i4 G3 vShort circuit and overload
protection
Key words:
; n* O9 C7 n# E/ W: Z4 |' C- Transformers
- Steady state conditions
5 T; w+ x% E, G3 Q; r4 Y- Short circuit
) T: K! J( F* v. Z% Q0 Y& ?8 `To be approved at the 49th
& W/ c% `  K3 T* C% ^5 P; y8 i# KCTL Plenary Meeting, in 2012
Question:
Inherently short-circuit proof transformers shall be tested by short-circuiting the output windings until
steady-state conditions are reached.
- |/ w2 U9 v  E) EIn the IEC 61558-1 “steady-state condition” is not explained. Referring to other standards for the meaning
; X( A7 d% L( q2 W6 Cof “steady-state conditions”. Or “thermal stability”. The thermal stability is the change of temperature of
less than 1°C per hour. So the following questions arise:
8 A+ ?$ D+ O' W/ m. X9 kIs it correct to record the temperatures after one hour when temperatures didn’t change (more than 1°C/h)?
) Y9 e" u1 p. r' Z+ w) k( SHow shall an inherently short-circuit proof transformer be assessed when the above mentioned
requirements are fulfilled, but the transformer is damaged 6h, after reaching the steady state condition, in
% e! Y4 C' X/ Q' }. U1 j7 q2 da way where safety will be impaired (the transformer bursts).
Decision:
Yes. The transformer should not be accepted because the insulated materials are not corresponding to the
- y7 l7 `9 R# W( Y' ^5 yinsulation class of the transformer.

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