Dielectric characteristics of a model transmission line in the presence of fire

The results of experimental investigation into the dielectric properties of air insulation in the presence of fire are reported. The experiments were performed on a 70-kV model transmission line. It is demonstrated that fire can reduce by half the breakdown voltage of a line. This reduction is explained in terms of the contributions of temperature, ionization, and flow of solid particles (ashes). The results add criteria for the design of transmission lines. The results are relevant to agricultural fires (e.g., the intentional burning of sugarcane fields under HV transmission lines)