The Wisconsin Public Service Commission in a Sept. 27 order approved a September 2011 application from Northern States Power Co.-Wisconsin (NSPW) to construct new 161-kV and 69-kV electric transmission facilities.
This project, known as the Stone Lake-Couderay Transmission Project, includes the construction of a new 161-kV transmission line between the existing Stone Lake Substation near Stone Lake, Wisc., and a new substation to be located near Radisson, Wisc. The project also includes reconstruction of an existing 69-kV line between the two substations. The project would be 21 to 33 miles long and would cost between $28.5m and $35.3m, depending on the final route chosen.
The local area in which the proposed project is located is bounded generally by Duluth, Minn., Eau Claire, Wisc., Bergland, Mich., and Wausau, Wisc. The transmission system in the area provides primarily local load-serving functions. The project focuses on the area between the Stone Lake Substation and the existing Osprey Substation located northeast of Ladysmith, Wisc.
In 2008, NSPW completed a load-serving study of the transmission system in the area, the commission noted in the approval order. NSPW found that the modeling results show that the project is needed to address thermal overloads and low voltage conditions resulting from expected load growth in the area after 2012 under N-1 contingency conditions. These N-1 conditions were identified as a loss of either the existing Stone Lake-Stone Lake Pump or the existing Big Falls-Whitetail 69-kV lines. Under these contingencies, NSPW told the commission that the maximum load that could be served in the Stone Lake-Osprey area would be 31 MW and 33 MW, respectively. In every year since 2004, the peak load in the Stone Lake-Osprey area has exceeded 31 MW, reaching a maximum of 37.5 MW in 2011.
NSPW’s modeling shows that after the proposed project is in service, the transmission system between Stone Lake and Osprey will be able to serve more than 50 MW of load. Load growth that would exceed this level likely will not be surpassed until other planned transmission system upgrades in the area are in service.
Enbridge Energy to add load in this area
NSPW said that Enbridge Energy, which operates a liquid petroleum pipeline in the area, intends to upgrade its facilities and add significant load to the existing 69-kV system in 2012 in the Stone Lake-Osprey area.
In addition, NSPW stated that the existing Stone Lake-Couderay-Trails End-Big Falls 69-kV line is, for the most part, about 50 years old. Major refurbishment work is required in the near future to ensure its reliable operation. NSPW said that adding a 161-kV circuit while reconstructing the 69-kV circuit will strengthen the transmission system serving the area.
NSPW told the commission that generation is not a reasonable alternative to the proposed project to serve the affected area. The nearest generation sources include the approximately 70-MW Bay Front plant, which is fired by a combination of fuels including wood waste, coal, and natural gas, and about 125 MW of existing hydroelectric facilities.
Because the generation source would have to be located in the Stone Lake-Osprey area to address the identified need, the Bay Front capacity cannot alleviate facility overloading resulting from an outage of the 69 kV Stone Lake-Stone Lake Pump or 69 kV Whitetail-Big Falls lines, the utility said. Because of their intermittent nature, NSPW determined that hydroelectric facilities are not an acceptable alternative to the proposed project. In addition, because the existing 69-kV Stone Lake-Couderay line must be rebuilt, the cost of adding other types of generation into the area would be greater than the cost of the proposed project.
NSPW intends to begin substation construction during the second quarter of 2013 and transmission line construction during the fourth quarter of that year. It anticipates that the project will be placed in service during the fourth quarter of 2014, the commission noted in the Sept. 27 order.
Bay Front a key to grid support while new transmission added
Incidentally, NSPW, which is a subsidiary of Xcel Energy (NYSE: XEL), plans to install a baghouse and activated carbon injection equipment to reduce emissions from boilers #1 and #2 at the Bay Front plant. NSPW applied Sept. 12 at the Wisconsin commission for a Certificate of Authority on this $18.5m project. These new controls would reduce particulate matter and mercury emissions and ensure NSPW achieves compliance with new U.S. Environmental Protection Agency rules.
In addition to ensuring NSPW meets EPA requirements, the installation of the baghouse and activated carbon injection systems will allow the plant to continue to provide needed transmission voltage and system support in northern Wisconsin, NSPW told the commission. The Bay Front plant, at its current rated and operating capacities, is needed to ensure transmission reliability for at least the next five to nine years, which is through the current expected life of the plant. It is unlikely that the Midwest ISO will allow the retirement of these boilers until the reliability concerns in the area are resolved or until other factors are addressed, including potential load growth expectations, the utility said.
While the current life expectancy of the Bay Front plant is through 2021, the company said it is in the process of planning for a 15-year life extension, through 2036.
NSPW is getting commission approval for $90m to $140m in transmission upgrades that will address some of the reliability issues, the utility said in the Bay Front application. These upgrades will also help meet North American Electric Reliability Corp. (NERC) standards if any of the boilers at Bay Front were to be retired. An additional $80m to $100m of long-term transmission investments will be needed, however, if load growth expectations continue to increase and to further ensure compliance with NERC standards if boilers #1 and #2 are retired, or more generally, if the Bay Front plant is retired, the company added.
These transmission projects could be constructed as early as 2018. However, logistic and work force constraints mean it is unlikely that all of the necessary projects could be built until the early to mid-2020s, the utility said.