Fast Linear Contingency Analysis

This paper reports on a linear contingency analysis program that computes linearized real power flow changes resulting from branch outages and generation or load changes. A modern formulation has been adopted based on the relation ΔP = Δθ rather than using current injections and the bus admittance matrix. For maximum speed in processing such a large number of contingencies, the explicit inverse (triangular portion) of H is computed by the back substitution method. Multiple branch contingencies require essentially the same time as would the same number computed individually. Multiple generation or load changes are handled most efficiently by a single repeat solution for Δθ using the sparse factors of H and a sparse ΔP vector. Explicit branch distribution and generation shift factors are computed only for display to the operator.