Optimal Transmission Switching in Electric Networks

Growing demand for electric power seems to necessitate new transmission lines, but obstacles to building these new lines are often extremely high. At the same time there is a national push for a “smarter” bulk electric grid, one that is more controllable and flexible. Optimal transmission switching is a straightforward way to leverage grid controllability: to make better use of the existing system and meet growing demand with existing infrastructure. In this paper we present the formulation for an Optimal Power Flow with optimal transmission switching. Using this formulation to dispatch generators, we demonstrate system savings both on benchmark networks, such as the IEEE 118 bus system, and large-scale networks, including the ISO-NE and CAISO systems. Savings found here range from 13% to 25%, which, in a multi-trillion dollar industry, can mean substantial savings. In addition, market settlements based on OPF with transmission switching are examined and discussed. We also present the formulation for, and savings possible with, a security-constrained OPF with optimal transmission switching—a more secure, if not more restrictive, formulation.