Analysis of HV Bushing (138KV) PF and Capacitance test results
Analysis of HV Bushing (138KV) PF and Capacitance test results
(OP)
After having a recent maintenance testing we observed the following C1 test results. The capacitance values are satisfactory but the PF values were increased for some bushings, when compared to Name plate values mentioned in the report.
We also observed change in oil color in the 34.5Kv bushing sight glasses.
My understanding is higher PF indicates the contamination and deterioration of Bushing’s insulating materials.
Would like to understand other's comments based on the test results and what can we do to mitigate this?

We also observed change in oil color in the 34.5Kv bushing sight glasses.
My understanding is higher PF indicates the contamination and deterioration of Bushing’s insulating materials.
Would like to understand other's comments based on the test results and what can we do to mitigate this?


RE: Analysis of HV Bushing (138KV) PF and Capacitance test results
2) Are these 34.5kV bushings rated for the full load rating of the transformer or your anticipated full load of the plant?
3) Can you please upload the data sheet of 34.5kV bushing?
RE: Analysis of HV Bushing (138KV) PF and Capacitance test results
HV bushing is 138KV
LV bushing 34.5 KV
The bushings are rated for full load capacity of the plant.
RE: Analysis of HV Bushing (138KV) PF and Capacitance test results
RE: Analysis of HV Bushing (138KV) PF and Capacitance test results
When PF increases to 2 times, better to conduct the test at narrow band frequency ( 40-400 HZ) If the bushing is defective (esp moisture ingress) you will find an excessive increase in PF at low frequency. Change the bushing without further waiting.
Please see clause 7.3 of IEEE C57.152-2013 Diagnostic testing of Transformers