Equivalent circuit of Zero Sequence Impedance of Transformers
Equivalent circuit of Zero Sequence Impedance of Transformers
(OP)
What can be understood from the equivalent circuit shown on the right of these circuits shown on the attachment? and How are they drawn?






RE: Equivalent circuit of Zero Sequence Impedance of Transformers
RE: Equivalent circuit of Zero Sequence Impedance of Transformers
Good SEL paper
https://cdn.selinc.com/assets/Literature/Publicati...
A series of lectures from IIT
https://www.youtube.com/watch?v=bmToCwpM1Ok
RE: Equivalent circuit of Zero Sequence Impedance of Transformers
A zero sequence voltage source is simply a single phase voltage. If you connect three leads to that source, you have a zero sequence voltage source that can be connected to any three phase transformer connection.
Consider a delta wye-grounded transformer connection. If I connect my zero sequence voltage source to the delta side, you’ll get no current flow because each corner of the delta will have the same voltage. This results in an open circuit as viewed from the delta side.
If I now take my zero sequence voltage source and connect the three leads to each leg of the wye and the grounded end of the source to the neutral end of the wye connection, you will have a complete circuit on each leg consisting of the leakage impedance of the transformer. Since the currents on the wye side are all in phase, this results in a circulating current in the delta winding, but no line current on the delta side.
In view of this, does the third diagram make more sense to you now?