Y-type insulator string has advantages of external insulation and reduction of corridor width. This paper establishes a 3D finite element model of Y-type composite insulator string of 1000 kV AC double-circuit transmission line, including tower, insulator, grading rings, phase conductors and other hardware fittings, the model is used to calculate electric field distribution of composite insulator and grading ring. Then the parameters of grading ring are optimized based on the electric field results. According to the results, the optimum parameters of the racetrack grading ring are R=700 mm, r=120 mm, H=200 mm. The results can give a reference for design of UHV AC Y-type insulator string.
UHV transmission can meet the needs of long distance and bulk capacity power transmission. Nowadays,1000kV AC transmission experimental demonstration project and ±800 kV DC power transmission demonstration project has been built,and put into operation in China,and UHV AC/DC transmission lines as the backbone network frame of strong smart grid have been planned.
Insulator string is an important part of UHV AC transmission lines, it is important for electrical insulation and mechanical support.Y-type insulator string combines the characteristics of I-type and V-type insulator string together,can prevent windage yaw,improve flashover voltages under wet and pollution conditions,improve the height of conductor, and compress the length of ceross am and the corridor width，Hence,it has advantages of exterbal insulation and reduction of coridor width. At home and abroad, researches have been made for conventiona l-type and V-type insulator strings，about the electromagnetic environment, external insulation characteristics, structural properties and so on. The results under appropriate research methods have been applied in practical engineering. The research of Y-type insulator string mainly focuses on external insulation test and mechanical performance. China Electric Power Research Institute(EPRI) carried out a research about flashovercharacteristic of Y-type insulator string under pollution of DC transmission line.The research shows that Y-type insulator string DC polluted flashover voltage is about 9% bigger than I-type when the Vangle is 110degrees,and salt of V part lose fast in contamination test.The voltage distribution of Y-type insulator strings for AC/DC 500kV transmssion line is measured by sphere gap method and corresponding measures are adopted to reduce the impacts of environmental factors. Hence, it is necssary to cary out researches systematically on string type,grading rings optimization,external insulation characteristics and insulation configuration.
This paper studies the electric field distribution of UHV Y-type insulator string by using FEM,and the parameters of grading ring are optimized.The results can give a reference value on the design of UHV AC Y-type insulator string.