±1100kV线路长串盘形绝缘子污闪特性研究

Research on Pollution Flashover Performance of ±1100kV Long Line Disc Insulator String

特高压直流输电技术可实现远距离、大容量的能源高效配置,相较±800kV,±1100kV输电效率和输电距离可进一步提升,经济社会效益显著。±1100kV线路塔头尺寸受绝缘子串长的影响,可通过长串人工污秽试验得到的污闪特性确定。为保证±1100kV直流工程的安全性和经济性,应在±1100kV全电压、全尺寸以及不同并联间距等条件下开展人工污秽试验,获得污闪特性。特高压直流试验基地的±1400kV/2A特高压直流污秽电源解决了电源在最高输出电压和大电流负载时的电压稳定性问题。人工气候罐的污秽试验系统突破了超长尺寸试品污秽试验雾的均匀性控制问题。这两项关键技术使得±1100kV等级全电压、全尺寸试验具备条件。在此基础上,开展了串长最高至15.6m、全电压至直流1100kV、并联时不同串间距（500~1000mm）以及最高至6并联的多串并联的直流污闪试验。通过±1100kV全电压下的长串试验,获得了绝缘子串长、并联串间距、串形和污闪电压的关系。结果表明,串长和污闪电压在±1100kV以下范围内呈线性关系。±1100kV绝缘子双串或多串并联时,为保证串间不相互影响,建议串间距大于600mm。根据概率分析,大跨越在采用多串并联时需进行串长修正,并计算给出了不同条件下的修正系数。采用升降法,试验获得了±1100kV长串绝缘子在全电压范围内的串长和闪络电压关系,给出了并联串间距对污闪电压的影响,以及多串并联对污闪电压和外绝缘设计的影响,研究结果可直接应用于±1100kV线路外绝缘设计。

UHVDC transmission technology can satisfy long-distance, large-capacity and high-efficiency energy allocation. Compared with ±800 kV line, transmission efficiency and distance of ±1100 kV is further enhanced with significant economic and social benefits. Head size of ±1100 kV line tower is affected by insulator string length determined by artificial pollution test of long insulator string. In order to ensure safety and economy of ±1100 kV UHVDC project, artificial pollution test should be carried out under conditions of full ±1100 kV voltage, full size and different parallel string distance to obtain pollution flashover characteristics. UHVDC ± 1400 kV/2 A test capacity in UHVDC test base has solved voltage stability problems within the maximum output voltage and under high current load. Meanwhile, test fog uniformity control issue of extra long size test sample has also been cleared out. These two key technologies make ± 1100 kV level full-voltage full-size test possible in practice. Based on that, in this paper, a series of DC flashover tests were carried out, including long string tests up to 15.6 m, full voltage tests up to DC 1100 kV, parallel string test from 500 to 1000 mm spacing and up to 6 parallel insulator strings. Relations between insulator string length, parallel string distance, string type and pollution flashover voltage were obtained with long string test under full ±1100 kV voltage. Test results showed that string length and pollution flashover voltage presented a linear relationship within ±1100 kV. When double parallel string or multi-parallel string are adopted in ±1100 kV project, the distance between string centers should be greater than 600 mm to avoid interaction between adjacent strings. String length correction of multi-parallel string should be considered in long span transmission tower design. According to probability analysis, the correction factor was calculated under various conditions. In this paper, based on up-and-down method,relation between insulator length and pollution flashover voltage of ±1100 kV long string was obtained within full voltage. Influence of parallel insulator string distances on pollution flashover voltage was investigated. Outdoor insulator design of multi-parallel insulator string was also analyzed. These results can be directly adopted in outdoor insulator design of ±1100 kV transmission line.