Computational Design for Overvoltage Protection of Photovoltaic Inverters, based on Metal Oxide Varistors

Protection equipment based on metal oxide varistors is the most common solution today in the field of low voltage surge arrester applications. All ZnO based varistors are power electronic devices made of n-type semiconductor polycrystalline ceramics, having a high degree of non linearity of current-voltage dependence. This paper presents an original algorithm applied for dimensioning low voltage varistors, used to protect the inverters located in photovoltaic plants. The algorithm consists in 3 steps, one for computing the height corresponding to the desired voltage, another for the determination of the diameter corresponding to a certain energy/volume absorption capacity, and, a third one which is a sort of safety test for conformity.