Mitigation of switching over voltages in uhvac system

For transmission voltages above 400 kV, transient overvoltages play a vital role. At greater transmission voltages, switching overvoltages become more significant as the operating voltages of arresters are relatively near to normal system voltage and lines are usually long so that the energy stored in the lines may be large. Switching overvoltages shape and magnitude change according to the system parameters and the network configuration. For reliable operation, the switching overvoltage must be less than 2 p.u. at the receiving end for events such as line energization and re-energization where the highest switching overvoltage occurs. These overvoltages are not desirable and can damage the insulation of the lines and associated equipment. This paper delves into the different methods to mitigate the switching overvoltages and ultimately concludes the best method to reduce the switching overvoltages in a 1200kV system.