±1100 kV直流U型结构穿墙套管空气间隙放电特性及间隙距离选择

Air Gap Flashover Characteristics and Selection of Gap Distances for ±1100 kV DC U-shaped Wall Bushing

±1 100 k V直流U型结构穿墙套管具有机械性能好、便于安装等优点,但U型结构穿墙套管端部均压环对墙体距离与对地距离相近,在设计中需要考虑这两类间隙的综合绝缘问题。因此,为保证±1 100 k V U型穿墙套管运行中的外绝缘安全,并系统掌握其电气间隙放电特性,采用均压环和钢架试品模拟±1 100 k V直流U型结构穿墙套管端部均压环对墙和对地电气绝缘间隙,开展了环对墙不同间隙距离、不同对地高度以及典型配置综合间隙操作冲击放电特性试验研究,获得了模拟±1 100 k V U型穿墙套管电气间隙的操作冲击放电特性参数,并结合系统操作过电压水平提出了±1 100 k V直流U型结构穿墙套管最小安全间隙推荐值,在海拔0、500、1 000 m的条件下,最小安全间隙配置取为12.1 m/12.4 m、12.6 m/12.9 m和12.8 m/13.1 m(均压环对阀厅墙体/对地)。

The ±1 100 kV DC U-shaped walt bushing has advantages of mechanical properties, better economy, and easy installation. However, the distance between grading tings on the ends of the U-shaped wall bushing and wall is approximate to the distance between grading rings and ground. In other words, there is a combined gap issue for the U-shaped wall bushing, which will reduce the flashover voltage of air gap. Therefore, in order to ensure the safety of the ±1 100 kV DC U-shaped wall bushing and grasp its discharge characteristics comprehensively, we experimentally studied the air gap flashover characteristics of the bushing by using the real-size grading tings and a simulation wall. Moreover, we experimentally investigated the switching impulse flashover voltage tests in different conditions, including different distances from end grading tings to the wall, different distances from end grading rings to ground, and the combined air gap. Taking insulation coordination into consideration, we proposed a suggested minimum safe insulation air gap distance for the ±1100 kV DC U-shaped wall bushing according to analyses of the test results, which were 12.1 m/12.4 m,12.6 m/12.9 m, and 12.8 m/13.1 m （ grading tings to the wall/to the ground） at altitude of 0 m, 500 m, and 1 000 m, respectively.