基于阻抗轨迹估计的自适应相间距离继电器

在双电源系统中，由于对侧系统助增电流的影响，保护测量到的阻抗会偏离故障线路的实际值，从而引起距离保护发生超越或缩短保护距离。正向经过渡电阻故障时，距离保护测量阻抗随着过渡电阻变化的轨迹可以利用故障前保护测量到的电压、电流，经过估算得到。通过对阻抗变化轨迹公式的推导和分析，提出一种基于阻抗轨迹估计的自适应四边形距离继电器的原理及实施方案。该继电器利用故障前系统正常运行时电压和电流的测量值，实时估计出阻抗变化轨迹，并自动调整继电器的动作特性。理论分析和仿真计算表明，提出的自适应距离继电器可应用于相间距离保护，可有效防止区外经过渡电阻故障时发生超越，同时在区内故障时提高耐受过渡电阻能力。

A Novel Adaptive Distance Protection Based on Impedance Locus Estimation

The existence of fault resistance may add an additional reactive or capacitive component to the impedance seen by the protection. This may cause conventional quadrangular distance protection to over-reach or under-reach at different system conditions. Impedance locus with fault resistance seen by the protection in different system conditions is analyzed in this paper. It is shown that the impedance locus of a certain system can be estimated by using pre-fault voltages and currents messured by the protection. A novel adaptive algorithm for high-resistance earth-fault digital distance protection based on real-time impedance locus estimation is put forward. Theoretical analysis and digital simulation show that the new protection with enhanced resistive tolerance can overcome steady-state over-reach.