Insulation Levels for VEPCO 500-Kv Substation Equipment

A detailed study has been made of the Virginia Electric and Power Copmany (VEPCO) 500-kv transmission sytem to determine optimum insulation levels for the substation equipment. Results of this study depend on both economic and technical considerations. For the VEPCO system, a 70% arrester can be used at the generator step-up transformer locations, and a 75% will be required at step-down substations. Adequate impulse and switching surge margins permit a transformer BIL (basic impulse insulation level) of 1,300 kv to be used at all locations. The most practical circuit breaker BIL, consistent with good engineering practice and economy of application, is 1,550 kv.