Study of improved load-tap-changing for transformers and phase-angle regulators: Final report

The feasibility of using solid-state switches in tap-changing transformers has been investigated and the application of high-speed tap changers as phase angle regulators in transmission and distribution systems has been examined. This study shows that it is not feasible to utilize solid-state switches as ''one-for-one'' replacements for mechanical tap-changing switches due to prohibitively high costs. Novel transformer winding and solid-state switch configurations have been identified which are, however, economically attractive. Costs and losses associated with various configurations have been calculated for system voltages ranging from 65 to 740 kV. The application of this type of tap change as a fast phase shifter for transmission line applications appears attractive. Limited system simulation studies have been performed to verify that a fast phase shifter of this type can improve transient stability, power oscillation damping and circulating power control. 23 figs., 6 tabs.