More and more applications of ZnO arrester in electrical system experienced more problems. One thing, that is still under some investigation, is the effect of multiple lightning strike to the performance of ZnO arrester. As we know, the design of ZnO arrester for transmission system and for distribution system differs in the point of view of the number of ZnO blocks. Transmission system, due to its higher nominal voltage than distribution system, has more numbers in ZnO blocks inside an arrester tube. In term of the current rating of an arrester, it is found that there is some different value of the current rating. The current rating of an arrester installed closer to electrical substation is higher than that of some further away from the substation. To the respond of a lightning impulse strike, the arrester will let a high value of impulse current flowing. It tends to heat the ZnO material of the arrester. If the number of impulse strike is quite high then it may give the effect to the change of the arrester performance. This condition will endanger the equipment that is protected by the arrester from lightning strikes. During this research, the scope of work is limited to making an impulse current generator toward to one having 8/20 microsecond wave-shape. This kind of impulse current wave-shape is the one that is used for studying the performance of ZnO block.
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