Modelling AC Arcs Developing along Electrolytic Surfaces Simulating Practical Polluted Insulator Using an Original Laboratory Model

The present paper comprises an experimental investigation into the prediction of the critical flashover voltage of polluted insulators energized with AC voltage using a multi-channel photo-multiplier (MCP) and high speed camera to observe the behavior of ac arc on electrolytic surface. In order to maintain an arc burning on a dielectric surface, the present work proposes a regression model for expressing analytically the experimental curves which is based on re-ignition conditions as important factor in determining the flashover criterion of a polluted insulator under AC voltage and, also the E-I characteristics of the ac arcs. The effects of the length of the arc discharge on its own characteristics, as well as on the cumulate voltage drops at the electrodes. It was found that the arc may propagate with a relatively low constant velocity before the critical length is reached, and then accelerate with discontinuities at much higher velocity. This observation and the dispersion of the calculated values found for the discharge constants could mean that the arc burns in different atmosphere for any arc length. Moreover comparison of computed results with the results obtained from other models, as well as experiments indicates a good agreement.