Study on the time-varying characteristics of AC local arc over the contaminated insulation surface

From laboratory experiments it was shown that the flashover voltage of the wet contaminated insulator was significantly influenced by the parameters of the local arc. An integrated optical and electrical diagnostic platform was designed in this paper, which was used to acquire the emission spectrum and electrical parameters of the AC local arc over the wet contaminated surface. The analysis of thermodynamic and electric results showed that AC local arc had a “static time-varying” feature. Hence, a new characterization method of volt–ampere characteristics of the AC local arc was proposed, and a time constant was introduced to describe the time required for the AC local arc to reach the stable state from the beginning. The relationship between the voltage gradient of the AC local arc and the leakage current amplitude was obtained for flashover voltage calculation. Special attention was also paid to the influence of environmental factors, such as air pressure and ambient temperature, on the arc characteristic. This work can enrich the investigation of the parameters of the local arc over the wet contaminated insulation surface and may provide useful parameters for flashover voltage calculation of insulators in service.