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Highlights • Using the experimental tests, the effects of longitudinal and fan-shaped non-uniform pollutions on the ac flashover voltage of SiR insulators are investigated and analyzed. • The experimental results indicate that the flashover voltage increases under longitudinal non-uniform pollution and decreases under fan-shaped non-uniform pollution, compared to uniform pollution. • A new flashover voltage correction factor under combined longitudinal and fan-shaped non-uniform pollutions is proposed based on the test results. Abstract The pollution non-uniformity in the axial and circumferential directions of insulator surface has a great impact on the ac flashover voltage. So far, few studies have been conducted about the flashover voltage performance of Silicone Rubber (SiR) insulators under fan-shaped and longitudinal non-uniform pollutions. Therefore, this paper aimed to investigate the effects of longitudinal non-uniform, fan-shaped non-uniform, and combined longitudinal and fan-shaped non-uniform pollutions on the ac flashover voltage of four different types of SiR insulators. The analysis of experimental results indicated that longitudinal and fan-shaped non-uniform pollutions compared to uniform pollution contributed to an increase and a decrease in the ac flashover voltage, respectively. The ac flashover voltage increases with the increment of longitudinal non-uniformity degree and decreases with the increment of fan-shaped non-uniformity degree. Furthermore, a new correction factor of flashover voltage under combined longitudinal and fan-shaped non-uniform pollutions has been proposed. For all types of insulators, the correction factor under different non-uniform pollution conditions ranges from 0.85 to 1.13. [ABSTRACT FROM AUTHOR]

This paper presents proper indicators for evaluation of the surge arrester condition based on the leakage current analysis. Maximum amplitude of fundamental harmonic of the resistive leakage current ( I mr1 ), maximum amplitude of third harmonic of the resistive leakage current ( I mr3 ) and maximum amplitude of fundamental harmonic of the capacitive leakage current have been used as indicators for surge arrester condition monitoring. The effects of operating voltage fluctuation, third order of voltage harmonic, over-voltage and varistor aging have been investigated to show the ability of introduced indicators for accurate diagnostic of arrester’s conditions. In order to have accurate values of stray capacitors, 3D-FEM has been used. Moreover, surge arrester model for calculating leakage current has been performed in ATP–EMTP. In addition, the signal processing has been done using MATLAB software. This study shows that the introduced indicators are proper criteria for surge arrester condition monitoring. [ABSTRACT FROM AUTHOR]