Primal and dual bounds for Optimal Transmission Switching

It has been suggested that Optimal Transmission Switching (OTS) may reduce generator dispatch costs by as much as 10%, saving millions of dollars annually. However, this conclusion has been deduced primarily from studies using the DC power flow approximation on two power networks derived from the IEEE 118-bus and RTS-96 cases. This paper is a systematic study of the OTS problem. Various OTS formulations are considered for computing primal and dual bounds on a variety of power networks. The results demonstrate that the DC power flow model is inadequate for solving the OTS problem, and that mixed-integer nonlinear optimization techniques are instrumental in finding high-quality primal and dual bounds. The paper also indicates that, on a variety of benchmarks, transmission line switching may bring generation cost reductions between 0% to 29%.