Rating and design of metal-oxide surge arresters for high voltage AC systems

Electric high voltage power system can effectively be protected by means of metal oxide surge arresters. The rating of a surge arrester must consider the highest voltage in the power system for thermal stability of the arrester itself as well as the standard lightning impulse withstand voltage of the equipment to be protected. There are different housing designs possible with different properties concerning mechanical strength, short circuit behaviour and costs. Arresters with porcelain housings off I er average mechanical strength at moderate costs, but secondary thermal break might occur after short circuit. Tube design polymer housings do have very high mechanical strength and extremely safe pressure relief behaviour but they are comparatively costly yet. Rod design directly moulded polymer arresters have only limited mechanical strength and good short circuit performance at relatively low price. However, there is a certain risk of unnoticed damage of the internal structure due to improper handling.