Experimental Study On Optimizing Of Grading Rings In750kV Transmission Line In Specific High Altitude Area

In recent years, as an effective anti-pollution tool, large numbers of silicon rubber insulators are used in the750kV transmission line in anywhere of Northwest of China. For the composite insulator, the electric field has close relationship with some problems in other lower voltage transmission lines, as the brittle fracture, aging and so on, and high-altitude areas have higher requirements for the insulation properties, so it is necessary to research the electric field and voltage distribution along the insulator strings to control the electric field distribution by the grading rings.Having summarized the calculation methods of electric field and according to the features of composite insulator, this paper selects finite element method. According to the actual situation of the750kV transmission line, ANSYS finite element software is used to establish2-D and3-D model for750kV composite insulator used in the areas with the altitude of1500-3000meter, the electric field intensity distribution and voltage distribution on the surface of the composite insulator are calculated in cases of insulator with and without grading ring. The effect of the grading ring for improving the electric field distribution on the composite insulator is studied by changing the parameters of the grading ring, and the proper parameters of the ring diameter, diameter of the ring tube, and the position of the ring in its vertical plane are investigated on the consideration of controlling electric field that cannot exceed the corona inception level.The calculation results show that grading ring can significantly improve the distribution of electric field, the greatest electric field strength on surface of the line end grading ring less than1.54kV/mm. The grading rings designed can meet the requirements of750kv transmission line. The result provides a useful reference for the external insulation design of750kV transmission.