运行中750 kV悬挂式避雷器电场计算及设计优化

建立了悬挂式避雷器置于地面时的2D轴对称有限元模型,对其电场进行了计算。定义了阀片电压偏差率并以此为目标函数,建立该目标函数与各均压环环直径和悬挂高度的拟合多项式关系。采用最小二乘法求解了拟和多项式的系数,得到避雷器置于地面时的最优结构,取得了与实测一致的结果。将避雷器悬挂于金属塔上处于运行状态时,考虑金属塔和母线效应时建立了3D有限元模型,计算了阀片电压偏差率分布。与置于地面时的结果比较,相同结构的避雷器置于地面和悬挂于金属塔上时,其阀片电压偏差率分布完全不同,因此不能将置于地面时测量到的阀片电压偏差率作为运行状态时阀片电压偏差率。处于运行状态下,当高、低压端阀片电压偏差率最为接近时,均压环达到理想配置。以此为原则设计的750kV避雷器阀片电压最大偏差率降低至11%,满足企业要求的不大于15%的指标,对西北电网750kV避雷器的制造具有指导意义。

Electric Field Calculation and Design Optimization in Running State for 750 kV Suspended-Type Surge Arrester

Symmetrical finite element model for the suspended-type surge arrester located ground is proposed to calculate the electric field distribution.The ratio of voltage warp(RVW) for the varistor is defined to simulate a polynomial of every diameter and suspended heights of the grading ring.The coefficients of the polynomial are solved by the least square method,then the optimizing structure of the surge arrester is obtained when located on the ground. Calculational results agree with experimental ones.While the surge arrester is suspended on the metal tower in the running state,considering the effect of the tower and the bus,a 3-D finite element model is established,and the distribution of RVW is calculated.It is shown that RVW is different based on the comparison of the distributions between the surge arrester on the ground and the suspended metal tower.Therefore,RVW of the surge arrester on the ground cannot apply to the suspended tower in the running state.In the running state for the surge arrester,while RVW of high and low terminals is nearly equal,the grading rings can ideally configured.Finally,RVW for the 750 kV surge arrester can be decreased to 11%.It satisfies the design target of less than 15%. Thus it is a important for the 750 kV surge arrester in the north-west power system.