Transmission expansion planning in the Western interconnection-the planning process and the analytical tools that will be needed to do the job

Within the Western interconnection there is a growing realization that the traditional long-term planning processes and analytical methods used to evaluate wires and nonwires alternatives fail to address many of the questions arising from deregulation and the perceived need for new infrastructure to facilitate markets and to assure reliability. In addition, homeland security issues may influence transmission infrastructure expansion. This paper describes the region´s evolving transmission expansion planning process and the role OPF´ modeling plays in aiding decision-making and consensus building. It identifies some opportunities for improvement in modeling, highlights two state-of-the-art models with capabilities that go beyond those of other models currently used for long-term transmission planning and makes a case for why we need to invest in better modeling and databases.