±800kV特高压直流开关场内避雷线间距分析

Spacing Distance of Shielding Wires for ±800 kV Ultra-high Voltage DC Yard

特高压直流开关场内设备对雷电流的耐受能力弱,因此对直流换流站的直击雷防护应采取比交流变电站更为严格的措施。针对此问题,采用雷电通道的分形模型分析了避雷针的保护范围,存在小电流绕击直流场设备的可能性,建议采用密集布置的平行避雷线对直流场内的设备进行保护。为了确定合理可靠的避雷线间距,根据站内设备耐受雷电流能力的不同,采用折线法、滚球法、先导发展法及分形方法等分区域对避雷线的保护间距进行了计算,分析比较了各种方法的分析结果,并提出了±800 kV特高压直流场内不同区域的避雷线间距推荐值,分析结果已用于我国向家坝-上海及锦屏-苏南±800 kV特高压直流场的避雷线设计。

The equipment in ultra-high voltage （UHV） DC yard have a low lightning withstand level to direct striking lightning, much stricter protection measures than those for AC substations should be adopted when designing the protection system of UHV DC yard against direct lightning strike. We analyzed the protection range of the lighting rod on the basis of the fraetal model of the lightning channel. Due to the lower probability of lightnings with lightning current directly striking the DC yard, densely packed shielding wires were suggested to be used to protect electrical equipment in the UHV DC yard. According to the lightning withstand level of different devices in the DC yard, the polyline method, rolling--sphere method, leader progression model ,and fractal model were applied to analyze the spacing distances in different regions of UHV DC yard. The results from different methods are compared, and the recommended values of shielding wire spacing distances in different regions of UHV DC yard are suggested, which have been applied in the shield wire designs of Xiangjiaba--Shanghai and Jinping Sunan ± 800 kV UHVDC yards.