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A comparative study of insulator materials exposed to high voltage AC and DC surface discharges

An experimental study was conducted, using the Inclined Plane Test method to determine the performance of typical power line insulator materials: RTV (Room Temperature Vulcanized) silicone rubber coated porcelain, HTV (High Temperature Vulcanized) silicone rubber and EPDM rubber. The constant voltage method was employed to evaluate the performance of the above samples when energized by ac and dc (both polarities) voltages. The relative performance of the different materials and the effect of the voltage types were investigated. The results show that the RTV silicone rubber coating exhibits the least erosion for ac voltage but shows extensive erosion in the case of negative dc voltage. The HTV silicone rubbers exhibit only minimal erosion when exposed to ac test voltage, but develop strong erosion under positive dc voltage, which can result in sample failure. EPDM experiences the least erosion for a negative dc voltage, but shows maximum erosion severity for ac voltage.