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transmission issues in pnw
Transmission in the Pacific Northwest
The Bonneville Power Administration is the largest transmission provider in the Pacific Northwest, though significant transmission is owned by others such as Puget Sound Energy, Pacific Power, and Idaho Power. All transmission systems in the Northwest are constrained in various locations – that is, they can carry no more power at certain times of the day and year. This map schematically shows Bonneville’s transmission constraints.
PacificCorp maps its system using a “bubble approach” where resources inside a given area are considered to have less of a transmission impact than when they need to be transmitted from one bubble to another. This graph shows Pacific’s “bubbles.”
Thus, all else being equal, a new renewable resource should be sited so that the power is delivered to a load on the same side of a transmission constraint or inside the same “bubble.” In some cases, a project can be sized and sited so that it is twinned with a particular load (retail customer). This type of arrangement is often termed distributed generation.
The same approach can be taken at the utility’s distribution (lower voltage) level. Within a utility’s system, there are often constraints at the distribution level. The value of a renewable project can be enhanced by siting a renewable so that it minimizes distribution
constraints.
In some cases, strategic siting can not only minimize transmission or distribution costs, but can actually enhance the system. Transmission and distribution constraints are usually directional – that is, the system is only constrained if the power is flowing from one direction to the other (say west to east in the Bonneville system). Building new generation near the load it is intended to serve would decrease constraint, if that load is currently drawing power from a constrained line. If the developer finds itself in a situation to be able to relieve a constraint, the price should be adjusted accordingly to reflect that additional benefit of the project.
For more discussion of interconnection issues and transmission costs, click here.
