中文摘要：

针对动车组车项绝缘子低温、凝露、大雾天气下易引发闪络事故，以受电弓绝缘子为研究对象，建立绝缘子表面水珠简化的平行电极3维计算模型。采用电场旋转角定义水珠的外加电场方向，研究了外加电场下最大电场增强因子与电场旋转角的关系，得到了2者之间的函数关系，以此分析了车顶绝缘子均压环的优化设置参数。研究结果表明：含分离水珠的车顶绝缘子表面电场畸变与外加场强方向有关，最大场强点位于等电位面与水珠的切点处，端切点处电场的畸变比项切点处更明显；考虑体积为1μL的半球形水珠分布于车项绝缘子不同位置的电场增强因子变化，优化高压端伞裙表面最大场强的原则，确定了均压环半径R=90mm、距离高压端高度H=49mm、截面半径r=20mm的最佳均压环配置方案。

英文摘要：

In order to solve flashover problem of the roof insulator at low temperatures with condensation and fog condi- tion on motor train units, we established a simplified 3D electric field parallel electrodes computational model to simulate the influence of separated droplets on pantograph support insulator surface electric field distribution. The electric field ro- tation angle was defined as the direction of the electric field forcing on droplet. The influence of the electric field rotation angle and the parameters of water droplets on the maximum enhancement factor of the electric field was studied, and the logic function model of the factor was proposed to achieve an optimized strategy of a grading ring setting. The results in- dicate that the electric field distortion is related with the electric field rotation angle. The maximum field strength is at the contact of the equipotential and the water droplets. The top points of tangent affect the electric field distortion more ob- viously than the endpoints of tangent. Based on comprehensive consideration of both the size of pantograph support insulator, direction of the electric field and principle of reducing the maximum field strength of high voltage side surface of insulator sheath, the best setting strategy can be determined as follows： the grading ring is radius 90 mm, the height apart from the high voltage side is 49 mm, and the sectional radius is 20 mm.