| Boundary Element Method (BEM) is one of important numerical method in engineering computation. Because of the merits that one dimension of calculated field can be reduced and that the computation possesses the analytical property, the BEM has been widely employed in various engineering fields. However, in electric field computation, the BEM has not much unfould and most of them are limited in the conventional BEM. In the flow field computation, although some achievements have been gained in solving the constant and uncompressible fluid flow by using BEM, but to the inconstant, compressible, nonlinear, transonic flow, such as the flow in the arc quenching chamber in SF6 high voltage circuit breaker, no any report has been published up to now for the reason that the basic solution of this kind of flow has not been found.Based on this situation and considering the facts that the breaking characteristic in SF6 high voltage circuit breaker is an important technologic index to judge the breaker capability, and that the insulation analysis in high voltage electric equipments is also relys on electric field computation. For all these reasons, the research on Boundary Element Method for numerical computation of the electric and flow field of SF6 circuit breaker have been proceeded comprehensively.In numerical computation of electric field, firstly, the degradation cell method and the potential particular solution method are presented for solving the singular-integral problem in coventional BEM. Secondly, the concept of the Boundary Contour Method (BCM) and Virtual Boundary Element Method (VBEM) in mechanic computation are introduced and the mathematical models and their discretized forms are established for numerical computation of electric field. In addition, considering the fact that many electric field issues in high voltage equipment can be summed up the axis symmetry problem in the final analysis, the mathematical model and its discretized form for calculating the symmetric electric field are also established based on the conventional BEM and a new method to solve the singular-integral of this kind of problem is presented.To the gas flow field in arc quenching chamber of SF6 high voltage circuit breaker, which is constant, compressible, nonlinear, transonic and has the complex and variable boundaries, first, the basic solution to the corresponding N-S equation for constant flow has been deduced basedon the basic solution of mass and momentum equations in N-S equation. Then the basic solution to the inconstant flow of N-S equation is deduced. Consequently, the foundation for solving the gas flow field in arc quenching chamber is provided.Following deducing the basic solution, the mathematical model and its descretized form based on the principle of Virtual Boundary Method are deduced.With these achievements in this paper, the electric field distribution of 40.5 kV vacuum interrupter and 500 kV SF6 high voltage circuit breaker with single break have been calculated and analysed. The gas flow field distribution in arc quenching chamber under different breaking distance and the breaking characteristic of small capacitive current breaking and short current breaking have been well simulated and analysed. The corresponding results have been compared with the results calculated by commercial software ANSYS and FLUENT. The results show that the methods presented in this paper are effective and feasible.
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