Fast response solid-state on load transformers tap-changer

This paper presents a new method for on-load tap changing of power transformers using solid state and vacuum switches. The tap-changing system is composed of solid-state devices (for example GTOs), fast response circuit breaker (for example vacuum interrupters) and a number of transformer taps. In this method, GTOs and vacuum switches with suitable on-off timing makes it possible to change taps over a short period. Simulation results show that changing two adjacent taps takes less than 100 ms which is much shorter than the 5 s required for the corresponding change by mechanical tap-changers.