Improving High Voltage Transformer Reliability through Recognition of PD in Paper/Oil Systems

Investigations carried out on artificial defects are fundamental for understanding partial discharge (PD) behavior in electrical apparatus and establishing expert system databases. In this paper, tests on artificial defects (realized both in the lab and on real transformers) for paper/oil insulation system are discusses. In particular, emphasis is given to bubbles (in free oil or between paper layers) and PD due to floating metal objects, as other PD sources have been discussed in previous works. In order to provide a thorough picture of PD phenomena in paper/oil systems, the PD patterns obtained in the lab are discussed and compared with those obtained from transformers. The results reported here indicate that recognition of PD source in paper/oil insulated systems is feasible thorough appropriate tools.