特高压直流对同塔交流线路的过电压影响分析

随着我国电力工业的发展，特高压直流输电凭借其在远距离输电上的优势而成为我国特高压发展的重要方向。局部地区电力走廊紧缺，使交直流同塔架设输电线路成为必然。当交直流导线同塔架设时，将在导线间产生很强的电磁耦合。主要研究特高压直流线路故障对同塔架设交流线路过电压的影响。根据规划中的锡盟—上海交直流同塔多回输电线路相关数据，采用电磁暂态程序建立了详细的直流换流站模型以及交直流同塔架设输电线路模型，研究了特高压直流输电线路故障对同塔架设的超高压交流线路的影响，并分析了不同故障类型、运行工况、耦合段线路长度、耦合段位置等因素对交流感应过电压的影响。结果表明，交流线路上的感应过电压幅值在交流线路绝缘水平允许范围内；直流发生接地故障时，交流线路通过耦合作用在直流故障弧道产生潜供电流。分析了交流线路不同换位方式对直流线路潜供电流的影响，并对限制措施提出了建议。

Influence of UHV DC Transmission Line on Overvoltage of AC Transmission Lines Built on the Same Tower

With further development of the electric power industry in China, the HVDC line, thanks to its advantages for long distance transmission, has become a promising trend in the UHV transmission technology. Due to shortage of power transmission corridor shortage in some regions, adoption of the AC/DC hybrid transmission lines on the same tower becomes inevitable. When DC/AC transmission lines are erected on the same steel tower, strong electromagnetic coupling will be generated between conductors and a series of problems arise from the interactions between AC/DC lines, among which the effect of DC ground faults on AC lines is the main concern in this paper. According to the parameters of Ximeng-Shanghai AC/DC hybrid transmission project under planning, in the paper, the detailed simulating model of DC converter station and hybrid transmission line with double circuits AC trans-mission lines and DC transmission line are presented, and overvoltage caused by the DC ground fault on DC sound pole and adjacent AC lines are simulated, and several influencing factors such as different DC fault types, different operation modes, hybrid lengths and fault positions, are considered. The simulation results show that the overvoltage levels on AC lines generated by DC line faults are lower than the permissible values of AC insulation coordination margin. The fundamental frequency secondary arc current will be generated through AC/DC coupling during DC pole-ground fault, which will interfere with the clearing of DC fault. Several factors of secondary arc current such as AC transposition modes, fault position and AC conductor disposal schemes are discussed in the paper, and finally some restricting methods are presented for the design.