Performance and Analysis of Controlled Switching on a Transmission System

Controlled switching is a solution for the reduction and elimination of high frequency transient currents and voltages that occur during the switching of reactive plant (shunt capacitor banks and reactors). This type plant may be frequently switched by system operators in order to maintain acceptable voltage limits and therefore if switching is uncontrolled, this may present significant power quality problems to the network as well as increased stress and reduction of lifetime to substation equipment. The most common and economical method of controlled switching is point on wave control of circuit breakers with individual pole operating mechanisms. By controlling the point on the voltage waveform that the switching device energizes or interrupts the load, significant inrush currents and transient overvoltage's can be eliminated. These methods are based on experience and analysis which specifically applies the Irish Transmission Network.