不换位输电线路产生的不对称问题及解决方法

在线路负荷较轻或系统黑启动的初始阶段,由不换位超高压输电线路参数不对称产生的负序电流可能导致发电机负序保护动作,引起发电机跳闸或阻止发电机并网运行而造成大面积停电,或损坏系统中的一些用电设备.文章利用三相潮流计算程序对不同输送功率和不同线路长度情况下的由输电线路参数不对称引起的负序电压和电流进行了计算和分析,并对通过合理设置线路串补元件及线路两端无源无功补偿元件参数来减小负序分量的方法的可行性进行了探讨.计算分析结果表明,该方法能够有效抑制由线路参数不对称产生的负序电流和电压.

UNBALANCE ISSUE CAUSED BY UN-TRANSPOSED TRANSMISSION LINES AND ITS SOLUTION

Under light-loaded conditions or at the initial phase of power system blackstart, the negative sequence current caused by unbalanced parameters of the un-transposed long distance EHV transmission lines may lead to cascading tripping of a number of generators then bring about large area blackouts or damage some utilization equipments. The negative voltage and current, caused by the unbalanced parameters of transmission line under different transmitted power and different length of transmission line, are calculated and analyzed by means of three phase power flow calculation program. The possibility of the method to reduce the negative sequence component by rationally configuring the serial compensation elements and setting up the parameters of the passive reactive power compensation elements at both ends of transmission line is researched. The results from calculation and simulation show that the proposed method can effectively restrain the negative sequence voltage and current caused by unbalanced parameters of transmission line.