STUDY ON THE NON-LINEAR CHARACTERISTICS OF METAL OXIDE VARISTORS

The Metal Oxide Varistor or MOV is a voltage dependent, nonlinear device that provides excellent transient voltage suppression. The current flowing through a resistor is directly proportional to the voltage applied across the ends of resistor. In case of a varistor, the current-voltage characteristics curve is not a straight line. A varistor is a component which has a voltage – current characteristics that is very much similar to that of a diode. This component is used to protect electrical devices from high transient voltages. They are planted in the devices in such a manner that it will short itself when a high current is produced due to the high voltage. The design of insulation is dependent on the surge voltage behavior of HV power transformer windings. The response of HV power transformer winding insulation for fast rising surge voltages which might have caused due to lightning over voltages, is dependent upon square root of the ratio of the total ground capacitance to total series capacitance of the winding which is termed as alpha [” α”]. Here in this paper the present computer simulation of HV power transformer model winding represented by 4 sections is analysed. The different alpha values of winding selected here are 5, 10 & 15. The MOVs are used in applications ranging from motor of few volts to High Voltage Transmission Lines. MOVs find applications in protection of High Voltage transmission system, DC motor switching, power supply surges, in the buck converter as surge arrester and many others.