Transformer inrush current - 2

[cherry2000]

Once more on the same topic..I could locate some literature for calculating the worst 1st cycle inrush, based on the Transformer parameters like flux density, dimensions etc.See attached.

Next, I tried my hand at calculating the reduction in inrush because of line reactance. The reduction was not as much as desired. 1540Amps reduced to 1340Amps approx for a 150kVA, 3Ph, Dy Transformer. The power supply cable was 4/0, 200m. Does anybody have any idea on the transient analysis program for carrying out a study?

It is my belief that accounting for source impedance & cable resistance will further lower the inrush value.

 

[cherry2000]

Slide no 6 from

http://www.transformerscommittee.org/info/F01/Inrush01.pdf

makes me believe that the inrush value will fall.

 

[dpc]

It is my belief that accounting for source impedance & cable resistance will further lower the inrush value.

Is someone disagreeing with you on this? The S&C white paper referenced in previous thread (I think) confirms this. The cable impedance effectively increases the source impedance.

 

[cherry2000]

I am looking for a rigorous calculation to get the final value. Thanks for the support.

 

[dpc]

There is no final value. The inrush depends on voltage phase angle at energization as well as remanence flux. You can estimate a maximum worst-case value, or get it from the transformer supplier.

Perhaps a transient program such as ATP can help - it may have already been modeled at some point, but you'll need a lot of specific data on the particular transformer of interest. And make quite a few assumptions.

http://www.emtp.org/

 

[slavag]

cherry2000
For what you need a final value?
Take a worst case,as Dave recommended.
Best Regards.
Slava