一种反应环流电流的平行双回线保护选相元件

针对目前反应电流全量的电流平衡保护受负荷电流影响导致相继动作区大或保护拒动，以及反应故障分量的电流平衡保护故障分量提取方面的问题，基于双回线的相序变换原理，得出了环流电流故障分量与系统参数无关的结论，由此得到了平行双回线各种单线故障时环流电流的特征，进而提出了一种平行双回线单线故障的选相原理及其元件。文中提出的反应各相稳态环流电流故障分量的选相元件，不受系统参数和过渡电阻的影响，并且稳态环流电流本身就是故障分量，在整个故障期间都存在，易于提取、误差小。与电流平衡保护相比，该基于环流电流的保护在理论上能够提高平行双回线保护的性能。EMTP仿真结果表明，该选相元件能准确有效地选出故障相。

NEW FAULT PHASE SELECTOR FOR DOUBLE-CIRCUIT LINES PROTECTIVE RELAYING BASED ON DIFFERENTIAL FAULT CURRENT COMPONENTS

Based on differential currents, this paper presents a new fault phase selector for the protection of double-circuit lines. After phase-sequence transformation of double-circuit lines, six phases are decoupled into six sequence vectors including the differential and common vectors, which are independent of each other. In particular, as the differential vectors are independent of system impedance, the characteristics of all kinds of differential currents and differential sequence currents for all single-line faults of parallel transmission lines are inferred. This paper takes differential current fault components as phase selectors. The principle of the fault phase selector will be free from the influences of system parameters and fault resistance. As it is easy to obtain the fault components of the differential current and its error is small, the protection theory for double-circuit lines will be better than the conventional current balance protection using phase currents or current components. The results of EMTP simulation show that the principle is accurate and effective.