Abstract
Important characteristics of metal oxide surge arresters depend on the duty of specified temporary overvoltage requirement due to Volt-Ampere characteristics. However, there is hardly any literature where the duty of surge arresters in non-effectively grounded system is investigated. Temporary overvotage of 1.43pu proposed in effectively grounded systems is too low compared with nearly √3pu in a line-to-ground fault.
The overvoltage due to the combination of a line-to-ground and load rejection, where not only main power circuit but also control system like AVR participate, is rare but probable as the severest. Here the duty of surge arresters to the overvoltage is clarified to various residual voltage levels and system conditions. The severest condition is the one in the system including a cable line because of the operation of UEL of AVR.
