Placement of STATCOM and series capacitor based on CCT assessment for transient stability enhancement

In this paper, an attempt has been made to determine the proper location of STATCOM and series compensator working independently as well as simultaneously for improving the transient stability of a multi machine power system. The transient stability condition is usually assessed by evaluating critical clearing time (CCT), i.e. maximal fault duration for which the system remains transiently stable. The CCT is obtained by increasing the fault time interval until the system loses its stability. The effect of variation of generator loading, reference source voltage of STATCOM and degree of compensation on transient stability condition has also been considered at various locations of STATCOM and series capacitor. The results indicate the importance of installing STATCOM to a power system due to their effect of not only on stabilizing the system voltages but also increasing the power system critical clearing time in case of unrepeated three phase ground fault. Increase in CCT can help in the reliable operation of the protection system and reduce the protection system rating and its cost.