DC flashover criterion and discharge elongation mechanism in an air–electrolyte interval

For a better understanding of the flashover criterion and discharge elongation mechanism, an experimental study was carried out in order to find flashover voltage and current according to the pollution amount. A simulation study was then carried out to assess the electric field distribution in the vicinity of the discharge that corresponds to the flashover experimental values. The obtained results show that the average value of the electrical field in the flashover gap discharge-electrolyte is high compared with the average value obtained in works devoted to the study of air breakdown in the vicinity of an electrical discharge. The average field value of these two systems is lower than the average field value in a metal pin-water system. This result confirms that the presence of an electric discharge weakened the dielectric rigidity of the air. The maximum values of the electrical field in the vicinity of the discharge are high compared with the value of the disruptive field of air at atmospheric pressure. Flashover is, therefore, possible if the electric field distribution along the leakage distance is sufficient for discharge elongation by a progressive breakdown of the air, by Streamer or Townsend mechanism, between the discharge and the electrolyte.