Performance Evaluation of Polymeric Insulators Subjected to UV Radiation

The reliability of the composite insulators used in transmission systems, attributes to a major factor in the uninterrupted power supply to the consumers. These polymeric insulators, due being organic in nature, get aged under electrical and environmental stress. UV is the major factor responsible for the aging due to surface deterioration. When these insulators are used in marine, industrial and agricultural areas, pollutants get deposited on its surface. Thus, its surface resistance gets lowered and the leakage current starts to flow on the insulator surface which attributes to the changes in the chemical structure of the polymer chain. This results in flashover, ultimately leading to the failure of the insulator. Leakage current is one of the important parameters which provide indication of the insulator's surface condition. In the present work, design and fabrication of the UV chamber was carried out. In this UV chamber, 11kV polymeric insulators were artificially aged for 1 and 2 years. The experiments were carried out to measure the leakage current on the surface of the insulator under polluted conditions. The results show there is a rise in leakage current with increase in aging of the insulators. FTIR results revealed a breakage of Si-O-Si bond at 1150 wave number due to decrease in surface resistance of the insulator. This is the prime factor responsible for the increase in the leakage current which may lead to flashover of the aged insulators at normal working voltages under contaminated conditions.