半波长输电线路差动电流分布特征及差动保护原理适应性研究

Analysis for Differential Current Distribution and Adaptability of Differential Protection of Half-wavelength AC Transmission Line

针对现有电容电流补偿方法不适用于半波长输电线路电流差动保护,且差动点的选取影响电流差动保护的动作性能的问题,从理论上研究了各种故障方式下半波长线路故障点位置与电流差动点变化后沿线差流的分布特征,研究结果表明,当故障点与电流差动点相差1500km时,故障相差动电流最小,电流差动保护灵敏度最低;非故障相差动电流最大,电流差动保护可靠性最低。当故障点与电流差动点一致时,故障相差动电流最大;非故障相差动电流接近0。同时对差动保护原理在半波长线路上的适应性也进行了分析,分析结果表明对于半波长线路现有电流差动保护已不能适用,除需要对差动点进行预估外,还需要定制专有的差动保护原理。

With the problem that the capacitive current compensation method is not applicable on half-wavelength AC transmission line and the determination of differential point has a significant influence on current differential protection, the theoretical analysis for the distribution of differential current when fault location and differential point vary, the results suggest that when fault point is 1500km away from differential point, the differential current for fault phase and the sensitivity index reach their minimum respectively, with current for non-fault phase reaching its maximum and reliability of differential protection being lowest. When the fault point and differential point coincide, the differential current for fault phase reaches its maximum and for non-fault phase approaches zero. An analysis was carried out for adaptability of differential protection and the results suggest that the conventional differential protection is not applicable for half-wavelength AC transmission line and there should be a new special kind of differential principle developed.