Performance Analysis and Enhancement of Concentric Power Swing Blocker in TCSC-Compensated Transmission Systems

In this paper, the performance of the Concentric Power Swing Blocker (CPSB) is investigated on transmission lines compensated with Thyristor-Controlled Series Capacitors (TCSCs). To evaluate the impact of TCSC operation on the time measurements recorded by CPSB, two analytical approaches are presented. The first approach is based on the Heffron-Phillips model, which is suitable for small-scale power systems, while the second relies on the rate of change of the power angle (delta), making it more applicable to large-scale systems. Both analyses demonstrate that the time measured by the CPSB increases when the TCSC operates in capacitive mode and decreases in inductive mode. Based on recorded time values for both pure power swings and symmetrical faults, it is concluded that CPSB remains a reliable solution for protection in power systems equipped with FACTS devices. Furthermore, a novel solution is proposed to detect three-phase faults that occur during power changes. Two indices are introduced to achieve this goal: (1) the static phasor estimation error of the current signal, and (2) a new pair of concentric characteristics that ensure accurate fault detection during power swings.