Figure 5.1 shows a diagram of the ZnO surge arrester fabrication process. The basic material used to manufacture metal oxide varistors is pulverised, very finely grained and highly pure (99.9 per cent) ZnO with a particle size of 1–10 μm. Several doping elements and specially prepared powders [43, 50] are added in the form of fine oxide powders. The concentration of the individual components range from