Designing transmission with a long-term vision

Federal, regional and state entities have long recognized both the need and the benefits of investing in new regional and inter-regional transmission systems – and of designing those systems "smart from the start." These entities have encouraged the development of transmission systems through adoption of various laws, policies and planning initiatives.

Since its inception in 2005, the TWE Project has been carefully planned in alignment and collaboration with leading transmission/electrical infrastructure planning groups. This work assures that the multibillion-dollar TWE Project:

• Connects cost-effective energy resources to the grid.
• Coordinates with other projects and with sub-regional planning groups.
• Adds system reliability, stability and capacity for the Western Interconnection, which is the power grid that connects all of the western states.

The TWE Project represents the type of regional transmission envisioned in multiple federal and regional policies and studies to connect the West's generation resources.

A pipe diagram of the Western Interconnection shows that the bulk of the existing transmission capacity, shown in gray, is built along the coast in a "C." It also shows there is limited capacity between the California/Desert Southwest and Intermountain regions. Limited capacity means there is limited access to both diverse renewable resources and to diverse load areas. However, adding the 3,000 MW DC line system and 1,500 MW AC line system of the TWE Project vastly expands the ability to directly and efficiently exchange resources between regions.

Cost-effectiveness

The Western Electricity Coordinating Council (WECC) is the primary entity responsible for coordinating and promoting bulk electric system reliability in the Western Interconnection. In 2010, WECC initiated a Regional Transmission Expansion Planning process that was funded in part by the U.S. Department of Energy. The first report was WECC's 10-Year Regional Transmission Plan, issued in 2011.

The 10-Year Plan showed that, with Wyoming's exceptionally high-quality wind, the TWE Project will provide the most cost-effective remote renewable energy resource alternative in the Western Interconnection.

The 10-Year Plan's economic results were consistent with previous studies by Western Electric Industry Leaders and National Grid that underscored the economic benefits of tapping Wyoming's high-capacity wind energy.

In 2014, the economic benefits of investing in new direct current transmission between California and Wyoming were confirmed in a study conducted by the DOE's National Renewable Energy Lab. The study found that the economic benefit of such a transmission line is likely to outweigh the costs, with benefit-to-cost ratios ranging from 1.6 to 3.6. Utilities typically consider a new transmission line project as a worthwhile economic investment if the benefit-to-cost ratio is 1.1 to 1.2.

Planning coordination

In addition to WECC, there are sub-regional planning groups that exist throughout the western U.S. As an interstate transmission system proposed to cross Wyoming, Colorado, Utah and Nevada, the TWE Project will interconnect multiple sub-regions. Therefore, in alignment with the importance of coordinating with these groups, TransWest has participated within the planning efforts of these sub-regions for several years as well.

System reliability

The TWE Project will be one of the largest transmission elements within the WECC system. It will up to quadruple the transmission capacity that currently exists between the California ISO and the PacifiCorp balancing areas.

The WECC Rating Process is designed to ensure that transmission projects are properly integrated into the existing transmission grid to enhance the overall reliability of the grid. This process for the TWE Project as a DC-only configuration was initiated in 2008, and this process for the TWE Project with a DC and AC configuration was initiated in 2018. TransWest is a WECC member.