Online condition monitoring of surge arresters based on third-harmonic analysis of leakage current

Surge arresters play an important role in maintaining the reliability and protection of the high voltage power systems. Various diagnostic online monitoring methods of surge arrester are based on the decomposition of the measured leakage current into their capacitive and resistive components. The arrester's resistive component of the leakage current, in particular, the third harmonic component, is known as to be directly related to the degree of degradation of the ZnO blocks. This paper proposes an online monitoring technique for the surge arrester under dry and pollution conditions when measuring either the total leakage current or both the internal and external leakage currents of three different types of surge arresters. This technique based on feature extraction of the magnitudes, frequencies, and phase angles of all frequency components of the real measured current signals using Prony analysis-Hilbert transform approach and MATLAB program. The observed results illustrate the viability of this technique for online monitoring of surge arrester. Furthermore, the effect of voltage harmonics on the measured leakage currents is investigated through surge arrester model simulation performed with PSCAD program.