10kV Megger Testing on Oil Filled Devices 1

[DTR2011]

We see specifications for 10kV megger tests on oil filled equipment from time to time. We own several 1kV and 5kV units, but often have to rent a 10kV device. Examples of equipment may be HV VT's, CCVT's, Power Transformers, etc. Typical testing specs often also call out for a "Doble" or Power Factor / Tan Delta Test @ 10kV.

Modern Insulation resistance test sets are digital and often read in the Terra Ohm range, so that is a plus.

I wonder what, if any, advantages exist using 10kV when a Power Factor test gives much more and better information? If the Oil is good, won't we be reading the DUT insulation in series with the oil, thus really only reading the oil?

 

[prc]

You are right. When you have PF test at 10 kV, megger test have limited value. I felt a 5kV test set is sufficient for EHV equipment. With the new oils of high resistivity (due to superior hydro cracking) real paper insulation is masked during IR measurements.