Fast Evaluation of Available Transfer Capability (ATC) Considering Integral Square Generator Angle (ISGA)

One of the concepts in restructuring the electric power industry is the ability to accurately and rapidly quantify the power transfer so-called as the available transfer capability (ATC). Accurate identification of ATC provides vital information for both planning and operation of the bulk power market in reserving transmission services. There are various methods used to determine ATC such as the DC power flow, AC power flow, optimal power flow and sensitivity techniques. These methods considered the transmission line and voltage limits as the constraints for ATC computation. This paper presents the determination of power transfer between two buses that takes into account the dynamic security constraint. The dynamic security constraint based transient stability has been found to be one of the limiting factors in determining the power transfer so-called as the available transfer capability (ATC). The multi-machine integral square generator angle (ISGA) index is used to measure the severity of stable and unstable transient events during the occurrence of line outage and it is considered as the dynamic security constraint of the ATC assessment. The determination of ATC considering dynamic security constraint has been performed on the 6 bus and 11 bus systems. Comparative study has been made between the cubic-spline interpolation technique and recursive AC power flow method in determining the value of ATC. Key-Words: Cubic-spline interpolation technique, recursive AC power flow method, integral square generator angle, available transfer capability and line outage.