±1100 kV输电线路Y型绝缘子串间隙放电特性及污闪特性分析

Analysis on Air-gaps Discharge and Pollution Flashover Characteristics of Y-type Insulator Strings for ±1 100 kV Transmission Lines

Y型绝缘子串通过缩短V型串单肢长度,增加下I串,从而缩短了横担长度,可达到优化塔头尺寸、降低杆塔单基指标的目的。针对特高压直流(UHVDC)输电线路开展了Y型绝缘子串的间隙放电试验及人工污秽试验,包括Y串2种V–I串长比例(8:1和7:2)下不同间隙距离的标准操作冲击电压试验,及3种等值盐密(ESDD)(0.05mg/cm^2、0.08 mg/cm^2、0.15 mg/cm^2)和2种串长(4.37 m、7.7 m)下的人工污秽试验,获得了±1 100 kV直流Y串绝缘子的空气间隙闪络特性和污秽闪络特性。研究结果表明:V–I串长比为8:1时,由于下I串长较短,因此容易产生冲击电压击穿放电,而当V–I串长比为7:2时,放电则较多地出现在屏蔽环对塔身;2种比例下,间隙冲击放电电压及绝缘子污秽闪络电压值相差不大,差别分别为2.8%和5%;直流Y串污耐压值与盐密变化呈幂指数关系,而污耐压值与串长呈线性关系;此外,Y型串与I串、V串试验结果对比表明,各串型间隙放电特性、污秽闪络特性之间无明显差异。研究结果可为±1 100 kV输电线路Y型绝缘子串间隙配置及污秽外绝缘配置提供参考,对我国±1 100 kV直流输电线路实现Y型串的应用和推广具有重要价值。

By shortening the length of V-string single leg,and increasing the lower I string,the length of the arm for Y-type insulator string can be shortened,thus optimizing the size of the tower head and reducing the tower single-base indicators.We experimentally investigated ±1 100 kV ultra high voltage direct current（UHVDC） gap discharge of Y-type insulator string and artificial pollution.The gap discharge test was performed with standard operation impulse voltage,and the V–I ratio was set as 8：1 and 7：2 with different distance between the conductor and the tower.In the artificial pollution test,the V–I length ratio was set as 8：1 and 7：2,the equivalent salt deposit density（ESDD） was set as 0.05,0.08 and 0.15 mg/cm^2 and the length of insulator string was set as 4.37 and 7.7 m.Finally,the air-gap flashover characteristics and pollution flashover characteristics of Y-type insulator strings of ±1 100 kV UHVDC were obtained.The test results reveal that when the V–I insulator length ratio is 8：1,breakdown will tend to occur under impulse voltage because the I-type insulator string is too short,while the insulat ratio is 7：2,discharge will tend to occur between the shielding ring and the tower.Under conditions of the two ratios,there is no significant difference between the gap impulse discharge voltage and insulators＇ pollution flashover voltage,and the difference is 2.8% and 5%,respectively.The DC pollution withstand voltage of the Y-type string shows an power exponent relation with the ESDD,and a linear relationship with the length of string.Besides,comparison of the test results of Y-type,V-type,and I-type shows that the string type has no significant differences in the gap discharge characteristics and the pollution flashover characteristics.The research results of this paper can provide an important reference for ±1 100 kV transmission line Y-type insulator string gap configuration and pollution external insulation configuration and they are of great value for the application and popularization of ±1 100 kV UHVDC transmission line in China.