Transformer IR Measurement
Transformer IR Measurement
(OP)
Question of testing the transformer: EHV Trasnformer:
220KV / 15 KV // YNd11 // 250MVA // ONAN / ONAF
Is it normal to test PI for Oil filled transformer?? I guess not. PI (IR 600 Sec / IR 60 sec) is not valid measurement for Oil Filled transformers due to the oil inulation.
PI is valid for dry insulation.
Any comments on this opinion??
Can someone provide good reference for trasnformer IR measurement techniques and result evaluation??
Thanks in advance!!
220KV / 15 KV // YNd11 // 250MVA // ONAN / ONAF
Is it normal to test PI for Oil filled transformer?? I guess not. PI (IR 600 Sec / IR 60 sec) is not valid measurement for Oil Filled transformers due to the oil inulation.
PI is valid for dry insulation.
Any comments on this opinion??
Can someone provide good reference for trasnformer IR measurement techniques and result evaluation??
Thanks in advance!!






RE: Transformer IR Measurement
I have rarely seen higher than 1.
Min acceptable IR for Oil Filed X'mers is given by CE/Sqrt(KVA), C=30, E = phase to phase voltage and KVA is ratign of x'mer.
PI is more valid for dry / solid insulation - dry X'mers or rotating machines - motor or generators.
Please provide you opinion on subject.
RE: Transformer IR Measurement
IR at min of 5kV, including PI. IR should be >5G, PI should be>1.0
TTR
Pf/Df on each bushing
Excitation test
Winding R on each tap
And oil sample including DGA
RE: Transformer IR Measurement
These are commissioning tests or maintenance tests or acceptance tests? Can you please clarify??
NCTHAI
RE: Transformer IR Measurement
A more sensible test for checking the dryness of trf internal insulation is power factor testing.
RE: Transformer IR Measurement
I have found (for HV oil equipment), the PI test to be a waste of time, even using modern test equipment (Tera Ohm range). Infinity/infinity = ????
As a quick test, prior to AC PF/DF/TD tests, the megger test is OK.
Just my 2 cents