A Proposed Resistive and Capacitive Current Decoupling Method for Surge Arresters

Resistive leakage current based condition monitoring is the most widely used technique to check the aging of metal oxide surge arrester (MOSA). Resistive leakage current extraction from total leakage current is important for good assessment of MOSA condition. Recently, several methods have been proposed for extraction of resistive leakage current such as a hybrid method. In this method, capacitive leakage current magnitude is determined by calculating its equivalent capacitance and considered MOSA capacitance as constant value. Actually, the MOSA capacitance is a function of frequency. This results in low accuracy in extracting resistive leakage current in this method. This paper aims to propose a newly developed technique. The proposed method is a phasor based decoupling algorithm for capacitive and resistive currents extraction. The proposed method is applied on newly and aged MOSAs at 120°C. To study the effect of aging temperature on the extracted MOSA resistive leakage current, MOSA is aged at another temperature of 135°C. To ensure the accuracy of the proposed method, experimental tests have been carried out on 11 kV MOSA. Measured leakage current and voltage signals have been utilized by the phasor method for comparative study. The obtained results validate the efficacy of the proposed decoupling method as well as a sufficient increase in third harmonic to fifth harmonic of the resistive component of current is noticed with the increase in aging duration.