Behavior comparison of corona inception and flashover voltage between HVAC and HVDC insulator

This paper presents the behavior of corona inception and flashover voltage of AC and DC insulators on both AC and DC test conditions. The tested insulator specimens were suspension insulators, each kind of the tested insulator consisted of surface coating and no coating. The tested results showed that the corona inception voltage of AC and DC insulators coated by semiconductor on both AC and DC test conditions were quite higher than that of the ordinary insulators especially on DC tested condition these insulators only flashover occurred. In opposite way, the flashover voltage of these insulators was lower than that of ordinary insulators. This data is useful to be guidelines in case we need to take AC insulators coated by semiconductor replace DC insulators in a DC transmission line system to reduce the cost of investment. Moreover, it is useful to select or design the suitable DC insulators for using in pollution area in Thailand as well