双断口结构对特高压SF_6断路器电场分布的影响分析

Influence Analysis of Double-break Structure on Electric Field Distribution of UHV SF_6 Circuit Breaker

特高压断路器中常采用双断口或多断口串联,但串联结构在开断过程中会产生各断口间电位分布不均的情况,导致断口电场分布发生改变。为此,基于能量扰动法求得1 100 kV双断口SF6断路器灭弧断口等效电容及断口对地等效电容,确定并联电容值,进而得到双断口分压比。再采用有限元法仿真计算了断口的非对称3维电场,定量描述、对比分析了550 kV单断口灭弧系统与1 100 kV双断口灭弧系统触头沿面电场强度,得出了不同灭弧单元的电场变化规律,以及双断口结构对电场强度分布的影响。结果表明,采用双断口串联结构时,灭弧系统的断口间电压分配不均匀,且分压比随着开断距离的增大而减小;进而导致断口间电场强度以及开断故障电路时电弧重燃风险增大。因此有必要对双断口灭弧系统断口结构进行优化设计。

The structures of double-break or multi-break in series are widely applied in ultra-high voltage circuit breakers. However, the potential among each break of a cascaded structure does not distribute uniformly during opening-breaking processes, and consequently changes the electric field distribution at each break. To this end, using the energy perturbation method, we calculated the equivalent capacitances of the arc-quenching break and the break-to-earth of 1 100 kV double-break SF6 circuit breaker, and determined the parallel capacitance, as well as the potential ratio between the double breaks. Then we simulated the asymmetrical 3D electric field of the breaks using the finite element method so as to quantitatively analyze and compare the electric field intensity on the surfaces of the arc-quenching chambers of 550 kV single-break and 1 100 kV double-break breakers, and hence to obtain the electric field variation of different arc-quenching units and the influence of double-break structure on the electric field intensity distribution. The results show that, for two breaks in series, the voltage divider is not balanced; meanwhile when the breaking distance decreases, the voltage ratio increases, consequently, the electric field intensity among breaks and the risk of arc reignition during the opening-breaking process of fault circuit also increase. Therefore, it is necessary to improve the double-breaks arc-quenching chambers.