DSH 709/06 Short circuit and overload protection

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广东安规检测
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DSH 709/06 % h. U+ r0 S2 ]" G' w

Short circuit and overload protection ) b, ?$ k1 n) O" P* h: ^" F

15.2

61558-1(ed.2)

1 G2 X  x$ B) b- H& eStandard(s): IEC 61558-1/2005 No. Year
DSH
0709
2008
Category: SAFE
" X: o- n! }  }2 YSubclause(s): 15.2
Developed by: ETF5
OSM/LUM
5 J+ e# a3 f) m) Z5 PSubject: Short circuit and
overload protection
- D$ n; S: ~- J0 U# G! t$ n% SKey words:
- Transformers
- Steady state conditions
- Short circuit
) O- u& A3 K& P0 TDecision approved at the
" K4 F9 {, L# A4 k  G2 r# S. S46th CTL Plenary Meeting,
! {7 T, m. A/ C( x& l) jin 2009
Question:
Inherently short-circuit proof transformers shall be tested by short-circuiting the output windings until
/ w: O. g7 {' L& x' ^. `( wsteady-state conditions are reached.
In IEC 61558-1 “steady-state condition” is not explained. Referring to other standards the meaning of
“steady-state conditions” or “thermal stability” is that the change of temperature is less than 1°C per hour.
So following questions arise:
1) Is it correct to record the temperatures after one hour when temperatures did not change (more
than 1°C/h)?
. E3 e0 V& y9 d" r) I2) How shall an inherently short-circuit proof transformer be assessed when the above mentioned
* g4 p3 b# a( |2 m  U% ?3 n1 Nrequirements are fulfilled, but it is damaged 6h after reaching the steady state condition in a way
where safety will be impaired (the transformer bursts).
Decision:
) t7 }, P0 ?* R% d" R# E" E1) Yes.
: Q& B1 T' L% Q$ B2) The transformer should not be accepted.

9 Y' }: R- N; t: P! p& W8 P# P
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