高压直流换流阀用绝缘子表面电场计算及均压环设计

Calculation of Electric Field Distribution Along Composite Insulator and Design of Grading Ring of HVDC Converter Valve

换流阀是高压直流换流站的核心装备,高电位区导体及绝缘子表面电场计算是实现小安全裕度下换流阀绝缘优化设计的关键。将换流阀内典型结构,如绝缘子、晶闸管等,简化为二维模型,在二维场中直接进行电场计算,可实现电场的准确快速计算。通过对二维、三维算例进行电场计算,证实了边界电场约束方程计算电场的精度在二维场中高于ANSYS的计算精度。因此在二维轴对称场中应用该方法对某换流阀绝缘子进行了表面电场计算及均压环设计,使绝缘子金具表面电场由7.55 kV/mm降为2.87 kV/mm,绝缘子表面电场由1.93 kV/mm降为0.9 kV/mm。最后,应用ANSYS软件在三维复杂模型中对均压环尺寸进行校验计算。文中工作为直流换流阀用绝缘子表面电场计算及均压环优化设计提供了一种可靠、实用的计算方法。

Converter valve is the core equipment of HVDC converter station, therefore calculation of the electric field surrounding conductors in high potential area and the surface of insulators is the key to optimal insulation design of converter valve under a small margin of safety. Many of the typical structures in the converter valve such as insulators, thyristors, etc., can be reduced to 2D model, and calculation in the 2D electric field is fast and accurate. In this paper, the 2D and 3D electric field example was calculated separately, it was found that the constrained boundary electric field equation is more accurate than the ANSYS in the 2D field. Then, the surface electric field of a converter valve＇ insulator was calculated with the constrained boundary electric field equation in axisymmetric 2D field, and the equalizing ring was designed as well. The electric field of insulator fitting＇s surface reduced from 7.55 kV/mm to 2.87 kV/mm, and the electric field along insulator reduced from 1.93 kV/mm to 0.9 kV/mm. Finally, the checksum calculation of the equalizing ring size was carried out in the complex 3D model, and results show that the method proposed in this paper is reliable and practical for the electric field calculation of DC convertor valve＇s insulator surface and optimal design of the equalizing ring.