Laboratory investigation on hydrophobicity and tracking performance of field aged composite insulators

Evaluation of the field performance of composite insulators is essential for maintaining the desired levels of reliability in power networks. Field performance of composite insulators depends on many factors, including the insulator design, material quality and service conditions experienced. The most critical part of the composite insulator is its external housing, usually made of silicone rubber having the advantage of recovering its hydrophobic properties in polluted conditions. Thus, condition assessment of the hydrophobic properties of the housing material especially under erosion and tracking processes is of major importance. In this study performance evaluation of the housing material of 150 kV field-aged silicone rubber insulators is carried out through physical, electrical and material analysis techniques. The hydrophobic properties of the housing material were found degraded to a different extent between field-aged insulators due to differences in material structure and pollution conditions. Hydrophobicity can be better assessed if the relevant diagnostic techniques are also applied after inclined plane tests.