The Study On Optimization Of Electrical Characteristics Of The End Fitting With UHVDC Disconnector

UHVDC transmission has the advantages of long distance,large capacity and low loss.As an important equipment of HVDC transmission,the design and manufacture level of HVDC disconnector has an important impact on the reliability of the whole system.With the improvement of power system voltage level,the requirements of corona discharge,radio anti-interference ability and external insulation of electrical equipment are more stringent.Therefore,it is urgent to optimize the design of UHVDC disconnector to meet the requirements of DC engineering.In this paper,the optimal design of UHVDC disconnector is carried out based on the impulse discharge test and electric field simulation analysis of disconnector.The main contents of this paper are as follows:In this paper,according to the calculation and simulation method of static electric field in electromagnetic field and the theory of finite element method,Soildworks software is used to establish the models of±800kV and±1100kV disconnectors.Combining with Comsol Multiphysics multi-physical field simulation software,the electric field distribution of±800kV and ±11 00kV disconnectors is simulated and analyzed,and the basic distribution of electric field intensity is obtained.On this basis,the operating impulse discharge test was carried out on the disconnector with ±1100kV double voltage-sharing ring structure to verify whether its external insulation characteristics meet the requirements,and the maximum field strength and frequent discharge position are basically the same.Based on the results of electric field analysis and operation impact test,the end metal fittings of ±800kV and ±1100kV disconnectors are optimized.By changing the end fittings parameters of UHVDC disconnector,the effects of ring diameter,pipe diameter,shielding depth and fracture distance on the electric field distribution of the disconnector are studied.By shortening the fracture distance and increasing the shielding depth of the equalizing ring,the discharge probability can be reduced.The original double equalizing ring structure is replaced by a fully encapsulated mushroom head to improve the electric field distribution and insulation level.In order to test the effect of optimization,the operation impulse discharge test of the optimized ±1100kV disconnector is carried out.The test results show that the full-encapsulated shield with mushroom head structure can meet the requirements.Most±1100kV converter stations are indoor converter stations.It is necessary to verify the safe distance between the top of the elbow of disconnector and the top of valve hall.In this paper,the discharge test of the elbow of disconnector to the top of valve hall is simulated by the method of gap discharge between elbow and ground.Finally,according to the simulation and test results,the recommended size of the end fittings of UHVDC disconnector is given.In this paper,the parameters and shapes of the end fittings of UHVDC disconnector are optimized by using the results of operation impulse discharge test and simulation analysis,and the optimization results are verified to meet the requirements of UHVDC transmission.The research content of this paper has a certain guiding role in improving the manufacturing level of DC disconnectors in China and the construction of UHVDC transmission project.