【摘要】 为了呈现、阐释和解决110 k V双回线路格构式复合材料杆塔在污秽性能试验中塔头局部放电这种罕见的现象和问题,首先介绍了典型设计的110 k V双回线路格构式复合材料杆塔结构特点,开展了真型试验塔头的污秽性能试验,观察到在塔头的玻璃绝缘子钢帽、节点金属螺栓等金属节点处有显著的局部放电现象。然后仿真计算研究了试验塔头的电位和电场分布,结合试验塔头涂污、但不进行喷雾的工频耐压试验以及金属螺栓周围采取涂覆室温硫化硅橡胶(RTV)涂料(提升介质表面介电强度)防护措施后的污秽性能试验,分析获得了塔头金属节点局部放电的机理:在导线试验电压激励下,塔头电位分布不均匀,绝缘子串两端电位差约为49.7 k V,约占试验电压的50%;在污秽和水雾同时存在的污秽性能试验条件下,防污性能较差的玻璃绝缘子串上产生了强烈的污层局部放电和电流;这些污闪电流电荷在金属节点上聚集,导致金属节点电场强度增强,达到电晕放电起始电场强度,引起局部放电。即承受电压较高、防污性能较差的玻璃绝缘子串是导致局部放电的根本原因和源头。据此,提出了采用加均压环的耐污型复合绝缘子替换玻璃绝缘子串的推荐防护措施,试验表明,该措施能有效避免塔头发生局部放电,而且塔头污秽闪络电压可高达145 k V,具有足够的防污裕度。更多还原

【Abstract】 Partial discharges happen at the heads of lattice composite material towers on 110 k V double circuit lines during pollution performance tests. In order to interpret and solve this unique phenomenon and problem, we demonstrated a typical design of lattice composite material towers for 110 k V double-circuit lines and conducted pollution performance tests of a designed full-scale test tower head. Significant partial discharges were observed around the steel caps of glass insulators and the metal bolts in nodes. Then we numerically calculated the distribution of electric field intensity and electric potential around the tower, and conducted additional relevant experiments to study the mechanism of partial discharges. The additional tests included power-frequency withstanding tests using contaminated tower head without spray wetting and pollution performance tests with protective measures applied to the meatal bolts, namely they were coated with room-temperature vulcanized silicon to increase the dielectric strength at their surfaces. It is obtained that, under the excitation of operating voltage on phase conductors, the electric potential distribute unevenly around the test tower head, for instance, the glass insulator string withstands a voltage of 49.7 k V, which is accounted for 50% of the test voltage. In the meantime, under the pollution test conditions including pollution and fog, discharge currents concentrate on the pollution layer of glass insulator strings(which perform relatively worse against pollution). Charges brought by these discharge currents gradually gather around the steel caps and metal bolts, improve the electric field intensity up to the critic value for starting coronas, and eventually lead to partial discharges. In conclusion, glass insulator strings with relatively worse pollution performance but withstanding high voltages are a fundamental source of partial discharges. ——Hence, a protective measure that substitutes anti-pollution composite insulators with strapping for glass insulator strings is proposed. Further tests have proved that using this measure can efficiently avoid the partial discharges in tower heads, and sustain the pollution flashover voltage of the true type test tower head up to 145 k V, possessing an adequate margin against pollution.更多还原