Contamination initiated flashover of insulators in generating stations

This paper analyzes flashovers of apparatus insulators that occurred in a 345 kV generating station. It has been shown that flashovers can occur with low levels of surface contamination and is attributed to factors such as, wind blown cooling tower drifts and highly nonlinear electric field distribution on the insulator surface. Computation of the electric field on the insulator surface confirmed that the spikes in electric field distribution created by dry and wet regions was sufficient to initiate multiple arcs along the insulator surface. The presence of moisture in the air gap between successive sheds provides additional electric field enhancement, but some contamination on the surface is required to initiate the flashover process. There is a need for improved models to explain flashover of insulators in EHV and UHV systems.