New manufacturing process for the metal oxide varistors used on low voltage surge-arresters

The effective protection of each type of sensible electronic piece of equipment against any type of over voltage (including direct or indirect lightning applied on power supply) is a big issue for power system specialists. Some of the most reliable electronic devices used in order to protect against overvoltages are all voltage metal oxide varistor based surge-arresters. These varistors are produced starting from a thick mixture of different metal oxides, where the main component (more than 80–90% as mass percentage) is ZnO. New improvements for these devices could be performed only by taking in consideration their mass production process, by placing different additives, having specific influences on the electrical and thermal behavior of the semiconductor material, mostly on their non-linear relation between the voltage applied and the current response as well as on their heat absorption capability. In literature there is no physical or mathematical model in order to assess the role of each dopant (additive) on the main characteristics. This is an experimental process which insures to the development of new semiconductor materials. This article will present a new manufacturing process (temperature and explain the influence of the sintering temperature on the electrical properties of two varsitor materials, with 2 and 5 additives.