新型自适应距离继电器

距离保护测量到的阻抗由于受对侧系统助增电流的影响会偏离故障线路的实际值，从而引起距离保护发生超越或者缩短保护距离。实际应用中往往利用零序电抗元件来解决这个问题，但对于相间故障则无能为力。通过分析发现，无论对于相间故障还是接地故障，当线路经过渡电阻故障时，距离保护测量阻抗随着过渡电阻变化的轨迹是一段圆弧，利用故障前保护测量到的电压、电流量可以估算出其圆心和半径。文中利用对阻抗变化轨迹的估算，提出了一种基于自适应电抗元件的四边形距离继电器的原理以及实施方案。理论分析和仿真计算都表明，所提出的自适应距离继电器除了能够有效防止区外经过渡电阻故障时发生超越，在区内故障时其耐受过渡电阻的能力也较常规四边形继电器有所提高。

New Type Adaptive Distance Relay with Improved Performance

The existence of fault resistance may add an additional reactive or capacitive component to the measured impedance seen by the protection. This may cause conventional quadrangular distance protection to overreach or under-reach under different system conditions. It is shown that the measured impedance locus with fault resistance seen by the protection is an arc that can be estimated by using voltages and currents measured by the protection. A novel adaptive algorithm for digital distance protection based on real-time measured impedance locus estimation is put forward. Theoretical analysis and digital simulation show that the new adaptive distance relay with enhanced resistive tolerance can overcome steady-state overreach for both phase to phase and phase to ground fault.