TRANSFORMER INRUSH CURRENT 3

[SRA007]

Dear Friends

could you pelase tell me that what is normal multiplying factor for transformer inrsuh current. for exammple if the HV Amps are 100 so by which factor we will multiply it.

 

[sibeen]

SRA007, I don't want to be too scathing here, but a 5 second google search would have yielded hundreds of papers, reports, oscillograms etc on the behaviour of transformer inrush. Perhaps a tad of research should be carried out before resorting to asking on this site.

 

[jraef]

And to tht point, the only viable answer we can give is ...

It depends...



"Will work for (the memory of) salami"

 

[jghrist]

Typical values for overcurrent protection coordination:
2 times @ 100 sec
3 times @ 10 sec
6 times @ 1 sec
12 times @ 0.1 sec
25 times @ 0.01 sec

These are typical for distribution transformers and will be conservative for larger power transformers.

 

[aruskuat]

There is specific value for 3 winding TR, here is :
0 – 1000 kVA : 9.5 – 12 x In

1000 – 10000 kVA : 5.9 – 11.4 x In

10000-100000 kVA : 3.6 – 7.5 x In

> 100000 kVA : 2.5 – 4.8 x In

but there is no specific value for tow winding TR, it can reach for 40 x, you can refer to IEC 60076. The condition can be worse if the sympathetic inrush occurs

 

[7anoter4]

See also:
IEEE Std 242-2001 Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems
CH.11.9.2.2.1 Transformer through-fault capability