64REF CT implementation
64REF CT implementation
(OP)
The restrict earth fault on my unit transformer 169MVA 161kv has been operating any time there is fault in the Grid. On one of the disturbance records , it was observed the polarity of the High side CT and neutral CT were the same. Am tempted to reverse the polarity of the Neutral CT. I would appreciate you advice on this.I have have upload the the disturbance and one line.






RE: 64REF CT implementation
I suggest you to check the CT connections once before chainging the polarity. The one line diagram is not quite complete in all details.
I assume that the REF is of High Impedence type. If that is the case, are the CT ratio and magnetising characteristics of the HV Side CT and Neutral Side CT identical?
If the Characteristics and ratios and the polarities are all same (and correct as well) I would then look into the relay configuration once. (Have come across few erroneous ones recently)
RE: 64REF CT implementation
RE: 64REF CT implementation
RE: 64REF CT implementation
If you can't get access to the CTs then you can prove the scheme stability by using an LV or MV generator connected to the LV winding of the transformer and using the HV earthing switches to 'steer' current to where you want it to flow, i.e. to force current to flow in the HV neutral. It's a simple test but it's also a fairly high power test which takes a bit of setting up, which is one reason why some commissioning guys on a completion bonus don't bother.
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RE: 64REF CT implementation