Studies and Reports > 2009 MN Biennial Report > NE Planning Zone > Needs: 6.3.14 Nugget-Hoyt Lakes

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6.3.14 Nugget-Hoyt Lakes

Tracking Number: 2009-NE-N1

Utility: Minnesota Power

Inadequacy. Mesabi Nugget Delaware, LLC is in the process of constructing a 1.5 millon ton/year iron nugget plant on the west side of the Cliffs-Erie facility site. Mesabi Nugget Phase I is expected to become operational during the fourth quarter of 2009. To serve this approximately 25 MW load, MP recently constructed a radial tap off the Hoyt Lakes to Laskin 138 kV MP Line #43 (43L). This approximately two mile radial 138 kV line terminates at the Skibo 138/13.8 Substation and was placed in service in early 2009. Phase II of the Mesabi Nugget project is expected to increase the company’s peak demand to approximately 50 MW. As part of this expansion, MP is evaluating methods to improve the reliability and security of service to Mesabi Nugget.

A map of the area is shown on the following page.

Alternatives. Alternatives include doing nothing, looping the #43L line into the Skibo Substation, and constructing a 138 kV transmission line between the Skibo Substation and the Hoyt Lakes Substation.

Analysis. In order to provide redundancy and improve the reliability and security of the high voltage transmission service to Mesabi Nugget, Minnesota Power is in the process of evaluating alternatives to provide a second 138 kV source to the Skibo Substation. The alternative of constructing approximately 2.5 miles of 138 kV transmission to loop the #43L line to the Skibo Substation is the least cost option. This alternative would provide two 138 kV sources to the Mesabi Nugget site, one from the Laskin Substation and one from the Hoyt Lakes Substation. The alternative of constructing approximately three miles of new 138 kV line between the Skibo and Hoyt Lakes substations would be significantly more costly because it would also involve modifications at the Hoyt Lake Substation. However, this alternative would provide additional regional benefits. Minnesota Power is in the process of determining if the benefits associated with the higher cost alternative are justified. As part of either alternative, Mesabi Nugget would add a second 138/13.8 kV transformer at the Skibo Substation.

Due to the size and operating characteristics of large industrial loads, distributed generation is typically not a viable alternative for improving reliability for these types of loads. For example, small generators are not capable of providing the in-rush current and reactive power required to start large electric motors. Mesabi Nugget’s load includes large electric motors, so distributed generation is not a viable alternative to improve reliability and security of service to the site

Schedule. The project in service date is currently estimated to be no sooner than late 2010. However, this project’s need and in service date are dependent on Mesabi Nugget’s expansion schedule. Electric supply requirements and timing will be adjusted as required to meet Mesabi Nugget’s electric requirements. A new transmission line would likely not require a Certificate of Need since it would be under ten miles in length, although a route permit from local government or the PUC would be required.

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