ABSTRACT
Insulation requirements are essential in high voltage (HV) system and equipment design. Overvoltages in a power system include temporary overvoltages, switching impulse and lightning impulse overvoltages; all are having different peak magnitude and shape of waveforms, although all are transient in nature. Any kind of overvoltage generates stress to the insulation of the electrical equipment and likely to cause damage resulting in outage of power supply. Overvoltage caused by surges can result in sparkover and flashover between phase and ground at the weakest point in the network. Overvoltage protective devices like surge arrestors or lightning arrestors are designed to withstand a certain level of transient overvoltage beyond which the devices drain the surge energy to the ground and therefore maintain the level of transient overvoltage up to a specific level. In this chapter all these aspects are detailed.
