Comparative evaluation of the leakage current and aging performance of htv sr insulators of different creepage lengths when energized by ac, dc+ or dc– in a severe marine environment

This paper compares the performance of HTV (high temperature vulcanized) silicone rubber power line insulators under AC and both polarities DC when subjected to natural pollution. The investigation was conducted at Koeberg Pollution Test Station (KIPTS) which is situated near Cape Town and is known for its severe coastal pollution and high humidity during the night. High rainfall is experienced during winter. Five insulators of different creepage lengths and of the same manufacture were energized by each voltage type, while being exposed to the environment for 310 days. The leakage current data of all insulators were logged, together with the weather data. Pollution levels were measured on a regular basis, using the ESDD (equivalent salt deposit density) method and directional dust deposit gauges (DDDG). High leakage current levels were recorded in summer due to the high pollution levels and high humidity. During winter, in contrast, lower levels of leakage current were recorded, confirming the washing effect of the winter rain. The leakage current levels for the silicone rubber insulators were of a similar order of magnitude for AC and positive DC, but lower for negative DC. Electrical discharge activities on the insulators were recorded at night and surface erosion was monitored at set intervals. A polarity effect relating to pollution performance and aging was confirmed on DC energized insulators.