Commissioning of Repaired 132kv/6.6kv Transformer

Drying Out!

..and contacting the manufacturer and/or a competent transformer engineer. The PI (Polarity Index) is just one measure of the transformer's insulation "health", if it is multiples above 2.0 then chances are the insulation is wet or dirty. Hopefully you have checked the DP (Dew Point) and BDV (Break Down Voltage) of the oil, done a DGA (Dissolved Gas Analysis), OA (Oil Analysis), pulled a vacuum, put on a nitrogen blanket, etc. prior to your PI test. Not all are necessary if the transformer was in service prior to the poor PI test, but if it has been severely overloaded, opened and/or the nitrogen blanket breached then PI might not tell the whole story.

First conduct the test on Oil.If its break down value is lower then use a filter machine and do it till moisture is removed.Clean all bushings with CTC.If above is not giving satisfactory results you have to dry out the winding by heating by circulating acurrent by applying a low voltage.Normally a welding generator can balso be used to get a suitable current which can give higher current at lower voltage.Then u have to do all precommisisiong tests

I think CTC (carbon Tetra Chloride) is banned. Even if it is not, you will be doing a great harm to the environment if you use CTC. One can go for CRC 226 instead.