PDSH 1021 Short circuit and overload protection

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PDSH 1021 8 k& J* v) n/ \" C* N8 `% ] 4 a3 V& I( S! R) F: L: Q

Short circuit and overload protection

15.2 + H* ~$ D7 L5 y8 ~, E2 h( c  @

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

2 U; Y; a! {6 u6 [/ X+ CStandard(s):
/ y9 N$ t* [! S% n1 c7 t' HIEC 61558-1
All editions
: \1 I1 W6 \. p- ^! GSubclause(s):
# {3 @, ~% b" K8 Q/ N* g! Q15.2
* R8 q5 _" F) O' O3 B5 UNo. Year
PDSH
1021 2010
4 `' \2 R  m, f" O+ cCategory: SAFE Developed by: ETF5
8 Y2 {) l" I; C$ {OSM/LUM
; @' ~" Y7 d3 v# V1 jSubject:
Short circuit and overload
protection
) ~; ~7 i: O0 e3 wKey words:
# ~! V$ T; J6 p) J# g- Transformers
- Steady state conditions
4 G! I2 u' o) i+ U4 e" g- Short circuit
To be approved at the 49th
CTL Plenary Meeting, in 2012
Question:
5 k) i& I/ {6 b7 e" BInherently short-circuit proof transformers shall be tested by short-circuiting the output windings until
6 Z. ?: p' U" n& L4 _% R6 f% J( gsteady-state conditions are reached.
In the IEC 61558-1 “steady-state condition” is not explained. Referring to other standards for the meaning
+ {( u: q' o; T" ]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)?
! B3 R4 L: W6 l) N. HHow shall an inherently short-circuit proof transformer be assessed when the above mentioned
' O, m3 c0 r8 H2 erequirements are fulfilled, but the transformer is damaged 6h, after reaching the steady state condition, in
8 q- g! [* `6 va way where safety will be impaired (the transformer bursts).
Decision:
7 Y& n0 k! L; V3 A0 tYes. The transformer should not be accepted because the insulated materials are not corresponding to the
+ L1 ~5 N8 t+ `* hinsulation class of the transformer.

8 a: M+ U/ U; n
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