Optimal Transmission Line Switching

Short Technical Overview

Bulk electricity networks are made up of generators that produce power, loads that consume power, and transmission lines that transmit power from generators to loads. Electricity networks are typically geographically vast and complexly interconnected, with thousands of lines connected in a web-like pattern under the control of a single network operator. In a network, generators are dispatched, or operated, in such a way that they meet the power demand of the loads but still respect power flow limits on each transmission line. Power flows from generators to loads along the lines in these networks in accordance with the laws of physics, which dictate that power flow along all lines in proportion to the electrical characteristics of those lines. This means the flow on each line is influenced by the properties of all other lines in the network. Therefore, it is possible to remove a line and improve the throughput of the system.

Optimal transmission switching is an innovative electricity grid management paradigm that takes advantage of this property of electricity networks. Transmission lines are switched in and out of the network in order to maximize economic efficiency of generation dispatch on a bulk electricity network. The optimal transmission switching problem can be formulated as an optimization problem with binary variables representing the status of each line. Using this formulation to dispatch generators and determine the status of each line, our team has demonstrated system savings both on benchmark networks, such as the IEEE 118 bus system, and large-scale networks, including the ISO-NE 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 have also formulated, and explored the savings possible for, a security-constrained OPF with optimal transmission switching—a more secure, if not more restrictive, problem.

Team Members

News Releases, etc

Optimal transmission switching; OR/MS-today Advertisement, February 2009

Related Papers

[FOF08]*
Fisher, Emily Bartholomew, Richard P. O'Neill, and Michael C. Ferris. Optimal Transmission Switching. IEEE Transactions on Power Systems, 23:1346-1355, 2008.
[HOF08]*
Hedman, Kory W., Richard P O'Neill, Emily Bartholomew Fisher, Shmuel S. Oren. Optimal Transmission Switching - Sensitivity Analysis and Extensions. . IEEE Transactions on Power Systems, 23:1469-1479, 2008.
[HOF09]*
Hedman, Kory W., Richard P O'Neill, Emily Bartholomew Fisher, Shmuel S. Oren. Optimal Transmission Switching with Contingency Analysis. . IEEE Transactions on Power Systems, 24:1577-1586, 2009.
[HFO10]*
Hedman, Kory W., Michael C. Ferris, Richard P O'Neill, Emily Bartholomew Fisher, Shmuel S. Oren. Co-optimization of Generation Unit Commitment and Transmission Switching with N-1 Reliability. . IEEE Transactions on Power Systems, 25:1052-1063, 2010.

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Conference Proceedings and Presentations

[INFRADAY+08] paper, (INFRADAY presentation)
Fisher, Emily Bartholomew, Kory W. Hedman, Richard P. O'Neill, Michael C. Ferris, and Shmuel S. Oren. Optimal Transmission Switching. Trans-Atlantic INFRADAY Conference on Applied Infrastructure Modeling and Policy Analysis, Resources for the Future, Washington DC, November 14, 2008.
[INFORMS+08]
Fisher, Emily Bartholomew, Richard P. O'Neill, Michael C. Ferris. Optimal Transmission Switching. INFORMS Annual Meeting, Washington, DC, October 12-15, 2008.
[INFORMS+08]
Hedman, Kory, Emily Bartholomew Fisher, Richard O'Neill, Shmuel Oren. Optimal Transmission Switching - Sensitivity Analysis and Extensions INFORMS Annual Meeting, Washington, DC, October 12-15, 2008.

Acknowledgements

This work has been supported by the Department of Energy under various grants, and the Air Force Office of Scientific Research under grant FA9550-10-1-0101 and its predecessors.