Review on characteristics, heating sources and evolutionary processes of the operating composite insulators with abnormal temperature rise

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This paper reviewed the research progress on abnormal temperature rise (ATR) of composite insulator. The ATR of composite insulator can be divided into two types, pointform temperature rise (PFTR) and bar-form temperature rise (BFTR). The composite insulators with PFTR only show significant temperature rise at high relative humidity (RH>70%), and the temperature rise locates in the area that 20 cm above the metal end-fitting. In low humidity environment (RH 70%) and low (<30%) RH. The temperature rise might reach more than 10 °C and the temperature rise area was wider, extending from the high-voltage end to several sheds units at the low-voltage side. And the GRP core in the composite insulator was found corroded. The heating energy was supplied by both conductance loss and polarization loss of the corroded GRP core. The decay-like degradation of GRP core was caused by the combination of damp condition, high electric field, discharge, mechanical load, et al and may evolve into decay-like fracture of composite insulator. The preventive methods concerning quality control, structure optimization, material modification and operation strategy were put forward. It was suggested that when PFTR was detected on the composite insulator, the inspection period of the insulator should be shortened properly. The composite insulator should be replaced as soon as the BFTR was detected.