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Transformer Inrush

Transformer Inrush

Transformer Inrush

(OP)
I guess this is a lot more complex than the simple question I ask but is there a simple rule of thumb for assessing transformer inrush currents on islanded generators?

I have a line up of 4x8MVA generators (11kV) and a 20MVA transformer (33/11kV) which needs to be energised from the secondary, with the minimum amount of 11kV generators on line.

(I have EDSA power system tool but I do not have the dynamics part of the package which includes a transformer model part apparently.  The only way I can assess this in the package at the moment is to substitute the transformer with a motor model of the same rating and set the starting current to be the equivalent of In x 12.  This gives an initial bus-voltage drop of 33% with 3 generators on line.)

RE: Transformer Inrush

You might want to search this forum - this topic has come up a few times.  Inrush will be limited somewhat by the internal impedance of the generators.  

I don't think it is worth the trouble to attempt a transient analysis.  

You might be able to energize the transformer as you are bringing up the generator field.  This is commonly done on large generators with unit transformers.  


 

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