不同海拔地区同塔双回±660kV直流线路杆塔空气间隙距离的选择

同塔双回±660kV直流输电工程直线塔布置型式在国内外尚属首次，其冲击放电特性与以往±500kV单回I串水平排列、±800kV单回V串水平排列时的冲击放电特性有很大差别。为解决我国宁东-山东同塔双回±660 kV直流工程杆塔空气间隙的选择和海拔修正问题，首先利用真型模拟塔头，对V型绝缘子串在不同夹角下的操作冲击和雷电冲击放电特性进行了试验研究，然后分别在低海拔地区(北京)和高海拔地区(西宁)，对±660kV同塔双回直线塔头进行了冲击放电特性试验，得到了海拔2000m及以下地区的海拔校正系数。最后，结合宁东-山东直流输电工程的实际情况，在1.8pu操作过电压下，对于海拔1000m及以下地区，±660kV同塔双回塔头的上层空气间隙距离建议为4.8m，下层空气间隙距离建议为4.9m；当海拔为2000m时，这2个距离分别建议为5.4m和5.5m。

Selection of the Minimum Air Clearance for ±660kV Double-circuit DC Transmission Line Tower in Different Altitude Areas

It is the first time to have the layout of ±660 kV DC double-circuit transmission line in the world. The impulse flashover characteristics of air gaps on ±660 kV DC double-circuit transmission line tower are in great difference with that of ±500 kV single-circuit transmission line tower and ±800 kV DC single-circuit transmission line tower. In this paper, the impulse flashover tests of air gaps with V-shaped insulator strings with different angles were carried out, and the impulse flashover tests with tower model of ±660 kV DC double-circuit line were carried out at lower altitude area(Beijing, China) and higher altitude area(Xining, China). Based on the practical situation of ±660 kV DC transmission project from Ningdong to Shandong, the altitude correction factors under 2 000 m altitude and lower are presented, i.e. while the switching overvoltage is 1.8 pu，the minimum air clearance of upper space and lower space on ±660 kV DC double-circuit transmission line tower is 4.8 m and 4.9 m respectively at the attitude below 1 000 m, when at the attitude of 2 000 m, the minimum air clearance of upper and lower spaces is 5.4 m and 5.5 m respectively.