A comparison of HVAC and HVDC contamination performance of station post insulators

Results of HVAC and HVDC (high-voltage alternating current and direct current) artificial contamination tests on station post insulators are reported. The tests were conducted using the clean fog method at various severity levels. The contamination behavior of station post insulators with semiconductive glaze was also evaluated and compared with the performance of post insulators with conventional glaze. For the latter type of insulator, different shed shapes were tested to study the effects of geometry on performance. The findings included the following: the critical flashover voltage (CFO) of the posts with conventional glaze, for a given minimum shed spacing, tends to increase as the specific leakage distance increases for both HVDC and HVAC tests. The ratio of the AC CFO (RMS) to the DC CFO also linearly increases as the specific leakage distance increases. The CFO per unit leakage distance decreases more rapidly with specific leakage distance for HVDC than for HVAC. Semiconductive glaze post insulators offer significantly improved contamination performance for both HVDC and HVAC