When power swings occur in transmission lines, the apparent impedance seen by the distance relay can shift toward the protection zone. This may result in unwanted trips in the protection system. This study proposes novel algorithms for detecting power swings and performing power swing blocking (ANSI 68) and unblocking through fault detection during power swings. The algorithms are free of settings and apply mathematical tools employed in commercial relays, such as the Fourier filter and symmetrical components. They are based on an analytical solution originally proposed in this study that demonstrates that negative-sequence phasors present a rotating behavior during a power swing, which can be used as a fundamental principle for power swing detection. The IEEE 9-bus electrical system is implemented in Matlab/Simulink to validate the proposed algorithms. The results show that the proposed algorithms effectively achieve blocking through power swing detection and achieve unblocking through fault detection. The latter function is shown to perform better than two algorithms available in the literature.

当输电线路中发生功率波动时，距离继电器看到的视在阻抗会向保护区移动。这可能会导致保护系统意外跳闸。本研究提出了用于检测电力波动和执行电力波动阻塞 (ANSI 68) 以及通过电力波动期间的故障检测解除阻塞的新算法。这些算法无需设置，并应用了商业继电器中采用的数学工具，例如傅立叶滤波器和对称组件。它们基于本研究中最初提出的分析解决方案，该解决方案表明负序相量在功率摆动期间呈现旋转行为，可用作功率摆动检测的基本原理。IEEE 9 总线电气系统在 Matlab/Simulink 中实现以验证所提出的算法。结果表明，所提出的算法有效地通过电力摆动检测实现闭锁，通过故障检测实现解锁。后一种函数的性能优于文献中可用的两种算法。