Analysis of partial discharges and their development into creeping discharges at solid/gas interface under AC voltage

Abstract

This paper is aimed at the analysis of partial discharges (PD) that occur at solid/gas insulating system and their development into creeping discharges under AC voltage (50 Hz), in a point-plane electrode arrangement, using the (ϕ q n) (phase, charge, number) matrix. The discharges number and the amplitude of their apparent charges are analyzed versus different parameters namely the applied voltage, the thickness of solid insulator, the pressure and type of gas (pure or mixture). The investigated solid insulators are discs of glass and the considered gases are SF6, N2, CO2 and mixtures (SF6 − CO2 and SF6 − N2). It's shown that the activity of partial discharges and their apparent charges increase with the applied voltage and decreases when the gas/mixture pressure is increased. For a given voltage and pressure, the maximum apparent charge q max values obtained with SF6 gas are much lower than those obtained with N2 gas and CO2. Also, q max in the positive half alternation is higher than that in negative alternation. The addition of SF6 gas in pure N2 and CO2 causes a decrease in the activity of PD and their maximum apparent charge q max . For a given voltage and type of gas, the activity and apparent charge of PD decreases as the thickness increases.