ABSTRACT
By deŠnition, a transient phenomenon is an aperiodic function of time and has a short duration. Examples for such transient* phenomena are voltage or current surges. A voltage surge is introduced by a sudden change in voltage at a point in a power system. Its velocity depends on the medium in which the surge is traveling. Such voltage surge always has an associated current surge with which it travels. The current surges are made up of charging or discharging capacitive currents that are introduced by the change in voltages across the shunt capacitances of the transmission system. The surge voltages can be caused by lightning, switching, faults, etc. HV surges on power systems can be very destructive to system equipment, and thus, they must be limited to safe levels.
