Improvement of total transfer capability using TCSC and SVC

Total transfer capability (TTC) is usually limited by overloaded circuits and buses with relatively low voltage. Flexible AC transmission system (FACTS) technology can redistribute load flow and regulate bus voltage, so it is a promising method to improve TTC. In the FACTS family, thyristor controlled series compensator (TCSC) and static VAr compensator (SVC) are the two main commercially available FACTS controllers. This paper presents the formulation and general procedure of TTC calculation using TCSC and SVC. The improvement of TTC using TCSC and SVC is demonstrated with a simple test system. Both thermal limit dominant case and voltage limit dominant case are investigated and the results show that TCSC can improve TTC in both cases while SVC can improve TTC only in voltage dominant case. The location of TCSC and SVC in the system also affects the improvement. Generally speaking, TCSC is more effective than SVC in improving TTC.