Qualitative Assessment of Power Swing for Enhancing Security of Distance Relay in a TCSC-Compensated Line

Incorporation of flexible AC transmission systems (FACTS) in the transmission network for improving its adaptability and resilience has a high impact on the behavior of power swing (PS) impedance characteristics and performance of protection schemes. This paper introduces a qualitative study on the effects of thyristor controlled series capacitor (TCSC) on the distance protection strategies for PS and also suggest modifications in the conventional distance protection logic. Power Swing Blocking (PSB) is a complimentary feature integrated with the conventional distance relay to detect PS. However, the addition of TCSC along with its fast-acting control loop results in the PSB scheme to experience a reduction in the recorded time by the timer thus leading to failure in detecting the encroachment of the apparent impedance to be a PS and thus causes maloperation of the distance relay. An Empirical Wavelet Based technique has been proposed to rectify these maloperations in TCSC incorporated transmission lines to contribute to improve stability by preventing undesirable tripping. The case studies have been implemented on the WSCC 9 bus system with the detailed dynamic model of the TCSC. The results demonstrate the efficacy of the suggested technique in overcoming the shortcomings of the conventional distance relay strategy.