tan delta

[haisa]

Hello Engrs
We conducted a tan delta test on a 30MVA, 132/33KV transformer recently using OMICRON CPC 100. At different voltages we had values like -6%, 0.5 % and 23%. What can we deduce from these. Iread that for good insulation the value should be around 0.007%
what does the minus sign imply.

 

[Skogsgurra]

There's something severely wrong with the measurements. Those numbers are not plausible at all.
Lots of moisture *could* be a reason. But those numbers are all over the place and indicate bad measurement practice. Or faulty equipment.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[collies99]

I surmise this is a 2 winding unit and what were you measuring as in what were your connections and test set hook-up ?

 

[unclebob]

It's quite possible the Omicron instrument is defective. Got a bad Doble last month.

 

[7anoter4]

I would test the oil moisture too.