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How to calculate zero sequence impedance for transformers

How to calculate zero sequence impedance for transformers

How to calculate zero sequence impedance for transformers

(OP)
Hi.

Can anyone advise any litterature explaining how to make an analytical calculation of the zero sequence impedance for different couplings of 3 phase transformers, say Dyn, Zyn,Ynd,YYn.

Best Regards
hhhansen

RE: How to calculate zero sequence impedance for transformers

(OP)
I have went through the references but is not able to find any litterature stating how to make a model of the zero sequence impdance and how to calculate it.

  

RE: How to calculate zero sequence impedance for transformers

Many of the listed references include discussion of the topic transformer zero sequence impedance.  The St. Pierre Short Circuit book is the one I regularly turn to.

RE: How to calculate zero sequence impedance for transformers

RE: How to calculate zero sequence impedance for transformers

A zero sequence set of voltages are all in phase.  This characteristic means that you can perform a test with a single phase source and simply jumper the source-side terminals together.  The load side terminals would be shorted together.

Analytically you can see what impact a particular winding connection will present.  For example, if the source winding is delta, if you apply a single phase source to a delta and jumper all the phases together, you have effectively shorted out each delta winding so no current can pass through this winding to the secondary.

If the source winding is a wye or star, then you can apply a single phase source to this connection.  By jumpering from phase to phase, you will energize each winding with the same source voltage and you will get current flow to the secondary.

You can look at the T&D Book, Wagner & Evans, Grainger & Stephenson or Charles Gross and others and find the equivalent circuit for a variety of two and three winding transformers.  Once you reflect on doing the test with a single phase source, it should make more sense to you.

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