I need to model a 80MVA transformer 132/33kV built in 1973. There is very little information on this transformer but I need to populate certain values in the model.

Where can I find typical zero sequence impedance values for this type of transformer?

The positive sequence impedances are as follows:

  • HV – MV = 15%
  • HV – LV = 22.9%
  • MV – LV = 4.9%

Here is the information given:


And the fields which need to be populated:


  • \$\begingroup\$ A reasonable assumption is that Z0 is about 85% of Z1. \$\endgroup\$ Aug 7, 2014 at 13:05
  • \$\begingroup\$ On further inspection, this appears to be a wye-wye transformer with buried delta tertiary. The above comment I made a year ago isn't really accurate for this case. Try reading some of the references I have cited in electronics.stackexchange.com/questions/195239/… . \$\endgroup\$ Oct 14, 2015 at 15:40

1 Answer 1


usually the 132/33kv transformers have a Y / D connection and th LV side is resistance grounded through zig-zag transformer and so they have a moderate zero sequense impedance. but some tests show that,

The zero-sequence impedance is usually given as a percentage of the rated phase impedance.

When the transformer has a three-limb core and no delta-connecter windings, the zero-sequence impedance is about 30...60 %. When the transformer has a delta-connected winding, the zero-sequence impedance is 0.8...1.0 times the corresponding short-circuit impedance (uk%).

(from Testing of Power Transformer – Measurement of Zero-Sequence Impedance)


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.