Reduced transformer insulation

THE DEVELOPMENT of the Thyrite (registered trade mark) Magne-Valve station-type lightning arrester with its improved lightning protective characteristics made it possible to reduce power transformer BIL by two insulation classes under certain conditions. This was the culmination of a 5-year program which had three objectives: (1) to obtain service experience with the new arresters used with high-voltage two-step-down transformers; (2) to get additional information on switching surges occurring in service, and their effect on strength of transformer insulation; and (3) to study the long-time steady-state strength of transformer insulation.