作　　者： (张启平）; (李晨光）; (万磊）;

机构地区： 国家电网公司,北京市西城区100031

出　　处： 《电网技术》 2017年第9期2743-2748,共6页

摘　　要： 半波长交流输电线路三相短路时刻的工频故障特性对线路绝缘、过电压抑制和暂态稳定具有重要影响。通过仿真现象提出研究问题,建立半波长单点送出系统三相短路的电路模型,理论推导短路时刻电流和最严重故障位置的计算公式,理论分析系统产生谐振的机理,研究严重故障点与系统开机台数、线路结构、电压等级的变化规律,研究短路时线路沿线电压的分布和过电压情况,并通过仿真验证理论分析结果。研究结果表明,长于1000km线路在部分长度区间发生短路时刻电流、功率可能激增,引发系统谐振,线路沿线出现严重过电压,需要采取必要的抑制措施;对于线路长度超过1000km的线路,严重故障点除应考虑首端、末端外,还应考虑离首端和末端距离为l=(π-t)/β处。对于常规长度的线路(线路长度小于1000km),不论是1000kV、750kV、500kV,线路沿线发生三相短路,系统不会产生工频谐振现象。线路发生三相短路后沿线电压最大值位于距短路点四分之一波长处;严重故障点位置与送端系统开机台数、接入系统强弱、线路结构、电压等级有关。 Fault characteristics of half wavelength AC transmission lines with three-phase short circuit have important impact on line insulation, overvoltage suppression and transient stability. The questions were introduced based on simulation in this paper. A three-phase short circuit model of the sending system from a single point with a half wavelength AC line was built. Formulas of short circuit current and the location where the most serious fault happens were deduced. The resonance mechanism was analyzed. Relationship between location of the most serious fault point and number of generating units, line structure, and voltage level was studied. Voltage distribution along the line and overvoltage during short circuit were also discussed. The theoretical analysis was verified with simulations. The results showed that, for a transmission line longer than 1000 km, if a short circuit fault happens in some section on it, the current and power might increase sharply, causing system resonance and serious overvoltage along the line, and necessary measures shall be taken. Beside the two end points, the point l=（π-t）/β away from the end points should also be considered as a serious fault point. For a transmission line less than 1000 km, no matter the voltage level, system resonance would not occur with a three-phase short circuit on the line. Maximum amplitude of voltage along the line was located at a distance of one-fourth wavelength from the short-circuit point. The location of serious fault point was related to number of generating units, system strength, transmission line structure and voltage level.

关 键 词： 半波长 交流输电 短路电流 工频过电压 谐振