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

This paper reviews the research progress on abnormal temperature rise (ATR) of composite insulators. The ATR of composite insulators can be divided into two types, point-form 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 is located in the area that is 20 cm above the metal end-fitting. In a low humidity environment (< 30%), there is little temperature rise (< 1.0 K). The polarization loss on the surface of the silicone rubber housing under an AC electric field after moisture absorption is the main heating source. Corona discharge in high RH causes surface degradation of the silicone rubber. The composite insulators with BFTR shows significant temperature rise at both high (> 70 %) and low (