Design of the control system for thyristor switched capacitor devices

A thyristor switched capacitor (TSC) device applied in 6 to 10 KV power distribution systems is described in the paper, which can switch on the capacitors without over inrush current and switch off at the instant when current is reduced to zero. The conditions of non-transient switch on/off are discussed first, and a voltage detecting principle for the medium voltage TSC is introduced. The proposed TSC is simple in structure. On-site test result shows that the zero-voltage detect method is correct and reliable, and the switch-on performance is satisfactory.