Frequency analysis of the leakage current under non uniform polluted conditions on one insulator plane model

In this paper, experiments are conducted in non-uniform contaminated conditions under 50 Hz applied voltage on a plane insulator model. This insulator simulates the 1512 L outdoor insulator which is largely used by the Algerian Company of Gas and Electric Power (SONELGAZ). The insulating model surface is contaminated with a conducting solution composed of distilled water and NaCl. The mixed solution has a conductivity of 1.2 mS/cm. The insulator surface is polluted by spraying the salt solution on the insulating region near the high voltage electrode. This study is aimed to analyze the distribution impact of the non-uniform layer on leakage current (LC) harmonics. These harmonics are examined with the Welch spectrum during the flashover process. Observation becomes more interesting when electric discharges appear on the polluted insulator. These discharges are a precursor sign of the total insulator breakdown. Thus it becomes necessary to monitor discharges growth to grant the safety of electric power systems. Results show that the flashover process can be analyzed with frequency components of LC in presence of the non-uniform layer. The increase of third harmonic of LC is directly related to the discharges occurrence. The breakdown flashover is prominent when the third harmonic of LC increases significantly and reaches practically the fundamental magnitude (50Hz). Consequently, low LC harmonics can be used as indicators to detect the increase of polluted layer width on the insulator surface.