Influence of cap-and-pin disc insulator profile on contamination flashover voltage

EHV and UHV projects can satisfy long-distance and high-capacity transmission demand of a.c. line. Projects in higher voltage level need insulators with higher mechanical load, whose structure height, diameter and other parameters are different from the parameters before. The influence of profile on contamination flashover characteristic is important for insulation selection and worthy to research. In this paper, 50% probable pollution flashover voltages of eighteen various profile cap-and-pin disc insulators at SDD=0.05mg/cm² and SDD=0.1mg/cm² are obtained separately by up-and-down method, in three fog chambers at China Electric Power Research Institute (CEPRI). The influence of cap-and-pin disc insulator profile on contamination flashover voltage are proposed. According to test results, outer sheds profile has better performance than under-ribs one. Moreover, specified creepage distance cannot be the only factor to be considered in outdoor insulation. Besides, outdoor insulation selection and dimensioning approaches are also discussed in this paper.