Arc propagation over electrolytic surfaces under power frequency voltage

Flashover of wet polluted insulation is caused by the propagation of arcs along the electrolytic surface. Several factors affect this flashover process under actual operating conditions. These include the variation in pollution resistance due to arc root movement and thermal effects. The difference between the discharge gradient and the effective pollution gradient is an important factor in determining the growth of the discharge. Moreover, the distribution of instantaneous power along the wet surface also affect the arc propagation significantly. This paper describes the different physical criteria controlling are propagation, over electrolytic surfaces under ac voltage application. Contrary to the existing concept of a critical point, from where the discharge takes the final leap to complete flashover, the results obtained show that there are critical zones, referred to as the growth period lying between 40 to 63% of the total pollution length, which depends on the degree of surface pollution and the nature of pollutants