500 kV同塔双回线路相序与换位对电流不平衡影响分析

Analysis of the influence of phase sequence and transposition on current imbalance of 500 kV double circuit lines on the same tower

广东电网区域内500 kV东鹏甲乙线负序电流超标引起保护告警,利用EMTP软件对线路三相不平衡情况进行了仿真计算,并提出了改造措施。结果表明,仿真计算与现场数据误差很小,论证了三相电流不平衡主要因线路自身参数引起;线路三相电流不平衡度随输送功率增大而增加,当线路按热稳控制功率计算时,零序和负序电流二次值均超过保护定值0.08 A,将发生保护告警且线路跳闸;建议在终端塔调整相序,使两回线路改为逆相序排列方式,可有效抑制三相电流不平衡。同塔双回线路建议在设计阶段通过电磁暂态软件仿真计算选取合理相序及换位方式,以避免三相电流不平衡过大的情况发生。

The negative sequence current of 500 kV Dongpeng double-circuit line in the Guangdong Power Grid area exceeded the standard and caused a protection alarm. EMTP software is used to simulate the three-phase imbalance of the line and propose improvement measures. The results show that the error between the simulation calculation and the field data is very small. It is demonstrated that the three-phase current imbalance is mainly caused by the line’s own parameters;the three-phase current imbalance of the line increases with the increase of the transmission power. When the line is calculated according to the thermal stability control power, the zero sequence and negative sequence current secondary values exceed the protection setting value 0.08 A, a protection alarm will occur and the line will trip;it is recommended to adjust the phase sequence at the terminal tower to change the twocircuit line to the reverse phase sequence arrangement, which can effectively inhibit the three phase currents are unbalanced. For double-circuit lines on the same tower, it is recommended to select a reasonable phase sequence and transposition method through electromagnetic transient software simulation calculation during the design stage to avoid the occurrence of excessive three-phase current imbalance.