Voltage and reactive power estimation for contingency analysis using sensitivities

Operational reliability is normally checked using contingency analysis, thus requiring the solution of the power flow problem under a wide variety of system conditions. As power flows are computationally expensive and approximate solutions are usually acceptable, fast estimation methods are used. Real power distribution factor methods provide a good trade-off between accuracy and speed. Reactive power and voltage sensitivities-based methods have not been as successful, partially because equipment limits are ignored. This paper discusses the estimation of post-contingency voltages and reactive power generation and flows using sensitivities. Employing piecewise linear estimates, the effect of equipment limits on the estimates is effectively captured. Representative results are presented using the IEEE 14 and 57-bus test systems. The results show that VAr limits have a significant influence in post-contingency voltages and reactive outputs and flows.