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A new algorithm for the design of metal oxide varistor surge arresters

Metal Oxide Varistors (also known as ZnO varistors) are built in many types of overvoltage protection equipment, being one of the most common solution for surge arresters. They have a higher non-linear dependence between voltage and current, and a relatively high heat adsorption capacity in case of normal overvoltage pulses. Their current is mostly activated by temperature, so overheating can cause a major damage. Researches could be carried out both for a new material as well as for technical solutions for a new design of this piece of equipment, by studying heat extraction and transfer inside a new varistor device. This paper propose a simple new device, used for low voltage applications, based on some supplementary brass masses added to the varistor, shaped as cylinders. They act like heat pumps at the beginning and as radiators at the end of the thermal process caused by a transitory overvoltage. A finite element model followed by some experimental measurements is also presented in order to confirm the new design, for permanent and transitory regimes.