Voltage sharing characteristics of V-type suspension ceramic insulator strings for UHV AC substation

Owing to the high voltage level, complex tower and insulator string structures, short phase distance and various arrangement forms of insulator string, the potential and electric field distribution of the insulator strings in 1000kV substation are more severe than that in transmission lines, and the voltage sharing characteristics of the insulator strings need to be researched deeply. With three dimensional finite element method, considering the influence of the tower, conductors, fittings and the interaction of three phases, this paper calculate the potential and electric field distribution of the V-type suspension ceramic insulator strings in 1000kV substation. The influence of grading ring, suspension status and mounting type to the potential distribution of insulator string is researched, the parameters of the grading ring including the diameter of grading ring, the mounting height of grading ring, and the tube diameter of grading ring are optimized, finally, the proper configuration of the grading ring applied to V-type suspension ceramic insulator strings in 1000kV substation was suggested. The research achievements by this paper have been successfully applied on the ultra high voltage (UHV) AC pilot project in China with great practical value to raise the reliability of the insulators and improve the electromagnetic environment in the 1000kV substations.