PDSH 1021 Short circuit and overload protection
http://decisions.iecee.org/icons/ecblank.gif PDSH 1021
Short circuit and overload protection
15.2
61558-1(ed.1);am1 & 61558-1(ed.2);am1
Standard(s):
IEC 61558-1
All editions
Subclause(s):
15.2
No. Year
PDSH
1021 2010
Category: SAFE Developed by: ETF5
OSM/LUM
Subject:
Short circuit and overload
protection
Key words:
- Transformers
- Steady state conditions
- Short circuit
To be approved at the 49th
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
of “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)?
How 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
a 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
insulation class of the transformer.
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