14 / 2018-07-29 17:07:55

Electric Field Calculation and Structure Parameter Analysis of Dumbbell Type Tri-post Insulator

GIL, Dumbbell type structure, Tri-post insulator, Finite element method, Structure parameters

Due to the prefect insulation characteristics, the applications of GIL in power system have been more and more extensive. Compering with the traditional overhead transmission line and cross-linked polyethylene cable, which can’t fit the harsh condition like the extreme environment, terrain complex and the limitation of floor space, GIL has a lot of advantages on electromagnetic environment, current capacity and stability. As for the unique characteristic of GIL, mature products of GIL are more preferable to the high voltage transmission field in some situation.
As the first 1100kV GIL in the world, Suzhou to Nantong ultra-high voltage GIL project in China has milestone significance for development of GIL engineering technology. It has the characteristics of long transmission distance, large buried depth and high voltage level. Tri-post insulator is one of the main components of GIL, playing a role in supporting center conductor and electrical insulation. The safety and reliability operation of power system are determined by the insulation performance of tri-post insulator to a certain extent. Defective design could make the electric field distortion prominent, which may cause partial discharge in GIL, or even lead to flashover. In this case, structure parameter analysis of tri-post insulator and improvement of electric field distribution are essential.
In this paper, the maximum value of electric field on the surface of metal insert and tri-post insulator were the major concern. Based on the structure of the GIL, which included central conductor, tri-post insulator, metal insert, particle collector and sulfur hexafluoride gas, the full three-dimensional (3D) finite-element method (FEM) model was built for numerical simulation. A lighting impulse voltage of 2400kV was applied on conductor while the metal insert, particle collector and shell were set to 0V as the boundary condition. After finite element calculation with COMSOL Multiphysics, electrical field distribution of GIL was obtained. Because the initial design of tri-post insulator couldn’t meet the requirement of the project, a new structure which called dumbbell type tri-post insulator was put forward. The electric field distribution of initial design of tri-post insulator and dumbbell type were compared and analyzed. Then the key parameters including radius of the post, width and inclination angle of dumbbell structure were changed to tell the effect law of dumbbell type structure to the electric field distribution.
The electric field distribution of initial design of tri-post insulator and dumbbell type were investigated. As was shown by the results, dumbbell type tri-post insulator had a better performance than initial design. Compared with the initial design, this new structure could effectively decrease the maximum value of electric field on the surface of the metal insert, which helps tri-post insulator achieve the design objective. In the meantime, this structure has little influence on the electric field distribution of the insulator surface. Different key structure parameter would have different influence on the electric field distribution. The smaller inclination angle of dumbbell could significantly improve the field distortion on the surface of metal insert. The results could provide valuable references for the design of UHVAC tri-post insulator in GIL.