Study on electrical properties and field solutions of water related heating of composite insulators on 500kV AC transmission lines

In 2011, a composite insulator in Shenzhen suffered fracture. Through infrared thermal test along the same and neighbor lines, 517 out of 1327 insulators presented with up to or over 0.5°C thermal increase. Early researches demonstrated that humidity was a factor to have effect on heating performance. In order to understand the potential mechanism of heating and provide precaution suggestions, we conducted FEM analysis on both thermal and electrical field; mechanical load test; electrical endurance test; mechanical, microscopic configurational as well as chemical analysis upon 9 problematic insulators and compared several ways to control end side field intensity. Defective interfaces were found. Polarization of insulation material after aging and water penetration was critical to heating. In order to reduce damage, decreasing the end side filed intensity was necessary to lessen heating loss as well as decelerate aging process.