Transformer bushing power factor

[shlim]

Hi all, is it possible to have bushing power factor test result to be more than 1 (one). Is this measurement different from the typical power factor for power system (unity = 1.0)?

 

[prc]

Normally bushing power factor is <0.7% (ie 0.007 pu) Typical values of new bushings will be less than 0.3 %. Maximum values that I came across is 10% (0.1 pu)during improper storage of some RIP bushings. In service never a bushing will be left energized with a Pf more than 1 %.

 

[shlim]

If I have a bushing that has 1.xx% pf, for two consecutive years, the measurement is not necessarily wrong? Instead it just showed that the bushing is in a very "bad" condition?

 

[prc]

Depends on the bushing. If it is RBP (resin bonded paper -an old type no more used) type bushing value is ok. Otherwise it is in danger zone esp original test value was <0.5 % .

 

[shlim]

Thank you prc. The one in question is OIP type bushing, so yes, it is in very bad condition. I think I am confused/mistaken with the pf for power system where the unity value is 1.