The Power Loss Calculation Model of Metal Oxide Resistors at Continuous Operating Voltage

Abstract

The heat generation of metal oxide resistor due to leakage current flowing through at continuous operating voltage constitutes the internal heat source of surge arrester. The internal heat source directly influences surge arrester stable operating temperature at continuous operating voltage, and affects the ability of surge arrester whether can return to stable operating temperature after absorption of the transient energy. Therefore, in order to obtain the thermal characteristics of surge arrester under transient voltage, the power loss characteristic of resistor in low electric field intensity region should be studied first. A numerical fitting method is proposed for the power loss of resistor in this paper. On the basis of a finite number of measurement points, the calculation expression of power loss variation is fitting with temperature and applied voltage ratio. A model of resistor used in surge arrester of UHV AC transmission system is taking for example. The AC power loss depending on temperature and applied voltage ratio is measured utilizing the resistor power loss measurement system. The fitting method proposed in this paper is implemented to obtain the power loss calculation expression of resistor. The power loss of resistor at different temperature and different applied voltage ratio is calculated. The power loss variation with temperature and applied voltage ratio is analyzed and compared with the measured results. It is shown that the calculation errors are within 12% in the temperature region of 60°C to 150°C, especially higher calculation accuracy about 120°C. The proposed calculation method for fitting power loss expression is valid, and the calculated results can be used in the calculation of surge arrester thermal characteristics as the internal heat source.