DEVELOPMENT AND PRACTICAL OPERATION OF PERFLUOROCARBON IMMERSED 275KVTRANSFORMERS WITH COMPRESSED SF6 GAS INSULATION

A perfluorocarbon (PFC) immersed 275kV transformer with compressed SF6 gas insulation has been under development. This paper clarified the A C partial discharge inception voltage and time characteristics of PFC immersed insulation and also clarified that a prototype 275kV 100MVA t hree phase transformer could be worked without any trouble during the long-term over voltage test. This prototype proved that it had the AC partial discharge inception strength of higher than 1.5 times of the A C test voltage and the lightning impulse breakdown strength of 1.5 tim es of the test voltage. A 275kV 250MVA three phase transformer was dev eloped and practically operated at the outdoor substation of Chubu Ele ctric Power Co., Inc. This transformer has been successfully operated until now and the detailed internal inspection of the transformer was carried out after one year and 9 months of the successful practical op eration and no significant abnormal condition was recognized.