Transformer magnetizing inrush current

[IndianTechEngg1001]

What is the ingredients of transformer magnetizing inrush current in terms of +ve, -ve and zero seq currents?

 

[electricpete]

Transformer inrush is highly non-sinusoidal (lots of harmonics).

+/-/0 sequence describes only one frequency (for example fundamental).

If wye connected, no zero sequence. Whether the fundamental contains unbalance and negative sequence, I’m not sure.

Typically as you know inrush is discriminated from through fault on the basis of harmonic content.


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[davidbeach]

If wye connected, no zero sequence.

You might be closer to the truth if you said for delta connected, but even then relays will see residual current in transformer inrush.

 

[electricpete]

I meant ungrounded wye.

Residual current considers all frequencies, zero sequence applies to only one frequency and I had in mind the fundamental. I believe there will be no fundamental zero sequence in ungrounded wye. (If I'm wrong I'm sure someone will let me know). Residual current clearly will be more relevant for relaying....I'm not sure what the OP is after when asking about sequence content.

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[jghrist]

With an ungrounded primary winding, there will be no zero-sequence current in the winding. There may be a small amount of zero-seq current in CT secondaries if there are CT errors.