Research on the applications of differential protection in TCT controllable shunt reactor

Based on the structures and operating principles of the thyristor controlled transformer-type controllable shunt reactor (TCTCSR), the performance of differential protection for this type of devices is studied. For TCTCSR, differential protection may not be reliable or sensible to the turn-to-turn fault and short-circuit fault of thyristors on the control winding (CtrW). To avoid the dead zone of differential protection for the internal faults in CtrWs, an improved current transformer (CT) configuration for differential protection and a zero-sequence overcurrent protection scheme are proposed.