特高压电晕笼防护段的设计

为了克服特高压电晕笼设计中电晕笼两端部的电场畸变,确保电晕特性测试准确有效,需要增设一定长度的防护段。采用三维有限元方法精细计算了电晕笼内导线表面电场分布,分析了导线弧垂对防护段长度的影响并提出了新颖的电晕笼防护段设计方法。计算说明新型结构的防护段能有效平滑和抑制电晕笼端部附近导线表面电场的畸变,使电晕笼内导线表面电场更趋于一致,提高了电晕特性试验的准确性。

Design of Shielding Sections of Ultra-high Voltage Corona Cage

Ultra-high voltage(UHV) corona cage is an indispensable testing facility for the research of the electromagnetic environment problem caused by the corona effects of UHV transmission lines.Because of the end effect,the surface electric field of the conductor is distorted near the two ends of the cage.The distortion property of electric field has an influence on the accuracy of the measurement results.Therefore,it is necessary to design shielding sections for controlling the effects on the testing results generated by the distortion of electric field.The length of the shielding section is determined by the length of distorted electric field section.In this paper,the electric field distribution of the conductor surface in the cage is calculated by using the finite element method(FEM).To simulate the practical case accurately,the sag of the conductor is considered in the calculation and the effects of different sags are analyzed.The results show that the influence of conductor sag can not be neglected in the design of shielding sections.Moreover,the larger the sag is,the longer the shielding section is.In order to ensure that the electric field values of the conductor surface in the measurement section approach to a constant,the sag of conductor should not exceed 60 cm in practical corona cage testing system.Finally,a novel design method of the shielding section in the corona cage is proposed.This design method can smooth the distortion of the electric field effectively.With the new type of shielding section,the length of undistorted electric field section increases greatly.As a result,the measurement results of the corona characteristics,corona loss and radio interference,become more accurate.