Condition assessment of outdoor porcelain insulator based on dielectric dissipation factor evaluated from non‐linear equivalent circuit

Abstract

This study presents a novel technique for estimation of contamination level as well as flashover voltage of outdoor insulators based on dielectric dissipation factor evaluated from the applied sinusoidal excitation and corresponding surface leakage current. Existing literature shows that surface leakage current of insulator is infested with odd harmonics though the applied voltage is sinusoidal in nature. The presence of harmonic contents in leakage current is due to non-linear characteristics of the insulator surface owing to formation of dry bands. The nonlinear characteristic of the insulator surface depends on its contamination level which in turn affects the corresponding flashover voltage. Therefore, the harmonic configuration in leakage current can be correlated with the contamination level on insulator surface and corresponding flashover voltage. Considering the fact, in this contribution, a non-linear equivalent circuit of insulator has been proposed based on harmonic components of the leakage current. For each harmonic component of the leakage current flowing through the insulator system, energy lost and energy stored in the system is calculated, which eventually enables to calculate dielectric dissipation factor. The proposed technique is applied for experimental investigation on 11 kV disc porcelain insulator artificially contaminated in the laboratory under controlled environmental conditions.