PDSH 1021 Short circuit and overload protection

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PDSH 1021 ' I- n; P/ G  k" W

Short circuit and overload protection 4 p$ _1 z6 h/ M: j

15.2

61558-1(ed.1);am1 & 61558-1(ed.2);am1 % x* v" g( @% e: |0 b5 _. z) R4 b

Standard(s):
IEC 61558-1
All editions
Subclause(s):
% f2 ?- q) M2 b2 L15.2
No. Year
* w" f& L# p- U0 M) G$ z( OPDSH
8 E% F/ e: V- ~* j. H9 J1021 2010
( a" w9 |8 b1 O' M. \Category: SAFE Developed by: ETF5
7 s" Q+ C% ^- @& u7 R/ H0 P' ]OSM/LUM
Subject:
Short circuit and overload
; P" a/ R9 v5 O3 Qprotection
' f% t0 r3 [) k" X' p+ w$ _Key words:
  c- ]) e8 \% v9 x! I5 b- Transformers
- Steady state conditions
4 {, ~+ [/ E; [3 P- Short circuit
7 V7 E# A( V8 y" _To be approved at the 49th
5 L5 B- s: _7 h" ]CTL 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.
In the IEC 61558-1 “steady-state condition” is not explained. Referring to other standards for the meaning
. K8 c! N* A) ^& Q) s9 Hof “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:
Is it correct to record the temperatures after one hour when temperatures didn’t change (more than 1°C/h)?
& T5 m# M5 \  G4 ?How shall an inherently short-circuit proof transformer be assessed when the above mentioned
# j0 \5 A) K* }# j5 Grequirements are fulfilled, but the transformer is damaged 6h, after reaching the steady state condition, in
+ S$ d7 y  @8 v' Ma 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
6 [9 T& n3 R0 C" q+ Tinsulation class of the transformer.

0 W) M  r6 y" j0 ^& B