DSH 709/06 Short circuit and overload protection

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DSH 709/06 % ^$ p8 F/ k* D; e5 n2 F0 y: u

Short circuit and overload protection : g9 K! Y# {$ Y  S- z

15.2 ; X% ]+ ]7 J# S; e# n8 M' A

61558-1(ed.2)

) k1 K& b; @. j" xStandard(s): IEC 61558-1/2005 No. Year
DSH
% d& u9 E8 n" U6 I: o, R0709
2008
Category: SAFE
4 Z$ h9 ^- Z1 E# E7 }8 n; G0 D; J, W* V% ]Subclause(s): 15.2
Developed by: ETF5
* \5 J0 K! O9 @5 C/ zOSM/LUM
6 N4 M- r7 v7 |/ n1 uSubject: Short circuit and
overload protection
! ~! E+ O' S! t2 H3 K8 cKey words:
2 \+ d/ r, V- a9 w) s- Transformers
- Steady state conditions
' T' n3 o9 Z# y3 K/ b8 y% G# ~; b- Short circuit
/ Z, H! d: C1 w5 |Decision approved at the
46th CTL Plenary Meeting,
1 a& v' T( Z/ ?! h: g! Din 2009
Question:
+ r  Z/ I2 O$ {( O6 V9 ZInherently short-circuit proof transformers shall be tested by short-circuiting the output windings until
) n3 Q+ m' r& isteady-state conditions are reached.
In IEC 61558-1 “steady-state condition” is not explained. Referring to other standards the meaning of
) t# J8 t3 [, \8 O* [2 w3 I# G“steady-state conditions” or “thermal stability” is that the change of temperature is less than 1°C per hour.
So following questions arise:
, k$ U* E+ q. W! Q' v9 h: I1) Is it correct to record the temperatures after one hour when temperatures did not change (more
9 Z5 ^) b- h. b  [. w5 Z" o! }- w& Kthan 1°C/h)?
8 j  K8 Q' v& `7 S( G4 [2) How shall an inherently short-circuit proof transformer be assessed when the above mentioned
' m% H$ A5 O; I5 N& J# brequirements are fulfilled, but it is damaged 6h after reaching the steady state condition in a way
/ K1 \9 _8 S3 m) x5 v" H' hwhere safety will be impaired (the transformer bursts).
Decision:
1) Yes.
. v. p% R. P+ z. J5 G6 s+ v2) The transformer should not be accepted.
, \) f3 D2 D! w
" z: Q) \/ j0 d