Abstract
This article extensively investigates the calculations of the compensation factor of the thyristor-controlled series compensator (TCSC), which are used to accurately evaluate the negative impacts of the TCSC on the performance of conventional distance relays. To broadly evaluate the distance protection performance, the TCSC was adapted to the IEEE 9-bus system as one of the interconnected transmission networks that are increasingly spreading to improve service reliability, reduce reserve capacity, and enhance system efficiency. In addition, IEEE 39-bus system, as a large interconnected system, is also examined to generalize the TCSC impact on different interconnected systems. To determine the precise impact, the impedance of the TCSC was calculated based on its practical design parameters. The impedance of the TCSC was examined as a function of transmission line impedance and firing angle. Both Mho and Quadrilateral distance relays were tested using the MATLAB/Simulink environment for different types of faults, fault locations, fault resistances, and firing angles for capacitive, inductive, and blocking modes of TCSC operation. In addition, distance relay performance was evaluated during power swing phenomenon in the presence of the TCSC. Simulation tests indicated the negative impacts of the TCSC on distance relay operation, which are not limited to over-reach and under-reach in faulty conditions but also to maloperation in dynamic disturbances that cause power swing phenomena on the protected line.
Highlights
The philosophy of flexible alternating-current transmission systems (FACTS) is to control power flow in transmission lines, enhance power system stability, reduce line losses and voltage control achievement based on power electronics
The thyristor-controlled series compensator (TCSC), which belongs to the variable impedance type of controllers, offers many advantages in power systems, such as fast and continuous control of the transmission line series compensation level, suppression of the active power oscillations, elimination of subsynchronous oscillations, and voltage support [2]
For low-impedance faults with high currents, both the metal-oxide varistor (MOV) and thyristor-controlled reactor (TCR) act and the TCSC operates in bypass mode; the overall impedance calculated by the distance relay increases beyond the real value, which causes relay underreaching
Summary
The philosophy of flexible alternating-current transmission systems (FACTS) is to control power flow in transmission lines, enhance power system stability, reduce line losses and voltage control achievement based on power electronics. The error in the distance relay performance due to the presence of the TCSC is reviewed in [7], the study did not consider TCSC practical modelling and the results have just been restricted to three phase faults only. We believe that there is still a need to assess the performance of the distance relay for the TCSC compensated lines in interconnected transmission networks covering all fault types and all modes of operation. This expression is calculated and helps in the accurate assessment of the distance relay performance for interconnected transmission networks possessing the TCSC. The operational modes of the TCSC can be categorized as follows [14]–[17]: bypass mode without MOV, capacitive boost mode with/without MOV, inductive boost mode with/without MOV, and thyristor blocked mode
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