Utilities across the nation have changed the way they operate to comply with Federal requirements designed to provide open access to the interconnected transmission grid to all potential buyers and sellers of bulk electricity. Western made these changes, too. We are developing a plan to voluntarily comply with the Federal Energy Regulatory Commission requirements (FERC Order No. 889/18 CFR 37.4) to separate our power marketing and transmission functions. Under this rule, transmission owners must not favor any entity's efforts to market power, even if the marketing is being done by a different function in the same company.
The goal of the functional separation is to prevent the use of inside information to gain market advantage. To comply, Western is making transmission availability and price information accessible to all market participants, both Western marketing staff and others, at the same time through a web-based information system on the Internet. Transmission providers use this Open Access Same-Time Information System, or OASIS, is used by transmission providers to post the availability of transmission services and provide other information as required by FERC. Under these new operating procedures, Western will restrict internal access to transmission information.
We filed Standards of Conduct for power marketing and transmission employees with FERC to fully implement Western's Open Access Tariff. They include:
Western operates four of 150 control areas within the three power grids in the United States and Canada. Western operates three of 30 control areas within the Western Interconnection. These three control areas are called the WAUM-West, or Western Area Upper Missouri-West, operated by our Upper Great Plains Region; the WALC, or Western Area Lower Colorado, which our Desert Southwest Region operates; and WACM, or Western Area Colorado Missouri, which our Rocky Mountain Region operates. Western's Sierra Nevada Region operates as a contract-based, sub-control area within the Sacramento Municipal Utility District control area.
Western's Upper Great Plains Region also operates a control area in the Eastern Interconnection, or eastern grid, called the Western Area Upper Missouri-East, or the WAUM-East.
Balancing supply and demand
Dispatchers must match resources (generation) to demand and delivery schedules. They must monitor and maintain system voltage. On an hourly basis, real-time dispatchers validate delivery schedules with each of the other scheduling entities. They also validate these schedules at the end of the day. In addition, they work to verify that delivery schedules for customers are balanced. They manage real-time e-tags—which document the scheduling of energy from an energy supplier and the reservation to transmit that energy—and they assist Automatic Generation Control dispatchers with energy purchases and sales for Area Control Error requirements.
They must also follow procedures and protocols for the regional reliability councils: the North American Electric Reliability Council and Western Electricity Coordinating Council.
Preventing service interruptions
Supply and demand must be perfectly in balance. Even small imbalances can cause voltage levels to swing significantly. To prevent damage, the grid is designed so that whenever unacceptable fluctuations in voltage levels or frequencies begin to occur at any point in the system (due to lines de-energizing), the generation in the area will immediately shut down. When shutdowns occur at the powerplants, the connections to adjoining areas are designed to automatically isolate the area where the imbalance occurs from the rest of the grid. So power that had been flowing over the line that failed automatically shifts to other, adjacent lines, reducing the risk of interrupting service to end-use customers or overloading lines.
The United States does not have one national power grid, but rather three separate grids—a Western grid, an Eastern grid and one in Texas, managed by the Electric Reliability Council of Texas. The electric system in the western United States —called the Western Interconnection—operates independently from the electric system in the eastern United States. Western operates primarily in the Western grid and owns and maintains more than 10 percent of the transmission lines in the Western Electricity Coordinating Council area.
Western also operates a control area (Western Area-Upper Missouri East) in the eastern grid, which is called the Eastern Interconnection. Western owns and maintains more than 30 percent of the transmission line mileage in the Mid-Continent Area Power Pool area within the Eastern Interconnection.
Direct Current ties
There are six DC ties connecting the Western Interconnection and the Eastern Interconnection in the United States and one additional DC tie in Canada. Western is associated with four of them. Western owns and operates the Virginia Smith (Sidney, Neb.) DC tie; owns 60 percent of the Miles City DC (Mont.) tie and operates it; and operates the David A. Hamil DC Tie Stegall (Neb.) DC tie (owned by Tri-State Generation and Transmission Cooperative.) Western also operates the back-to-back DC Converter Station project in Rapid City, S.D., owned by Basin Electric Power Cooperative and Black Hills Power and Light. The station can transfer up to 200 MW or power between the Western Electricity Coordinating Council in the Western Interconnection and the Mid-Continent Area Power Pool in the Eastern Interconnection. The other two U.S. ties are Public Service Company of New Mexico 's Blackwater N.M., DC tie and the El Paso Electric and Texas-New Mexico Power Company's Artesia, N.M., DC tie. In May 2005, Xcel Energy commercialized the latest High-voltage DC, or HVDC, tie in Lamar, Colo. This provided up to 210 megawatts of capacity between its operating companies of Southwestern Public Service in the Southwest Power Pool and Public Service Company of Colorado.