中文摘要：

110kV同塔四回输电线路因换位困难而存在较为严重的三相不平衡问题，在考虑输电线路长度、杆塔相间距离和导线相序布置等影响因素的基础上，利用PSCAD软件对110kV同塔四回输电线路进行了仿真建模，提出了同塔四回输电线路三相不平衡度的计算方法，分析了影响因素对输电性能的影响程度。仿真结果表明：随着输电线路长度的增加，输电线路的零序不平衡度和负序不平衡度均增大；随着相间距离的增大，输电线路不平衡度减小；在八种典型的相序布置方式中，逆相序配置方式的总体不平衡性最小。

英文摘要：

110 kV transmission line on the same tower has severe problem of unbalance for difficult in transposing. The influence of line＇s length, the type of tower and different layouts of phase sequence on unbalance of four-circuit transmission lines is analyzed by PSCAD. Through comprehensive comparison and analysis, it is concluded that, with the increase of length, the ze- ro sequence imbalance and negative sequence imbalance are in- creased. The simulation results show that the imbalance will in- crease with the increase of length. For the interphase distance, it is found that the imbalance will reduce when the distance in- creased. For the phase arrangement, eight kinds of typical phase sequence arrangement are adopted and results show that, the unbalance factor of reverse configuration method is comparatively small. 3