Transmission & Distribution

We invest in transmission and distribution upgrades and new construction to meet customers’ needs, maintain system reliability, and enable renewable resource additions. We're a leader in the CapX2020 initiative, a regional transmission effort in the upper Midwest by 10 utilities. We also were involved in three Midcontinent Independent System Operator, Inc. (MISO), multivalue transmission projects (MVPs). These projects reliably and economically enable regional public policy needs, provide multiple types of regional economic value, or provide a combination of both regional reliability and economic value.

As part of capital spending from 2020 to 2024, we expect to spend approximately $170 million on regional transmission projects and $157 million on distribution projects.

Miles in Operation

Transmission Lines
  2017 2018 2019
345 kV 729.0 729.0 890.8
230 kV 494.0 494.0 496.7
115 kV 878.8 886.0 915.9
69 kV 209.5 209.5 209.5
41.6 kV 3,763.5 3774.6 3781.0
Distribution Lines
24 kV and below  2,655.0*  2,664.6* 5778.8

*2017 and 2018 distribution values exclude distribution attached to transmission structures and distribution inside city limits.

Our studies indicate that Otter Tail Power Company’s transmission and distribution losses as a percentage of our total energy is approximately 10.35%, which has been slightly rising over time due to an increase in load creating more losses on our lower voltage transmission system and distribution facilities. 

Regional Transmission Development Enabling Renewable Resources

We are an owner in three MVPs that have been energized within the last five years. These projects include:

  1. Brookings County-Hampton Transmission Line, a 250-mile, 345-kV line from Brookings County, South Dakota to Hampton, Minnesota energized on March 26, 2015;
  2. Big Stone South-Brookings County (BSSB) Transmission Line, a 70-mile, 345-kV line from Big Stone South, South Dakota to Brookings County, South Dakota energized on September 8, 2017; and
  3. Big Stone South-Ellendale (BSSE) Transmission Line, a 163-mile, 345-kV line from Big Stone South, South Dakota to Ellendale, North Dakota energized on February 5, 2019.

Representing just over $1 billion in total transmission investment, these projects have added a significant amount of transmission system capacity to enable renewable resource additions within our region. As of the end of 2019, these three MVPs, in conjunction with the fourteen other MVPs across MISO, have enabled over 2200 MW of new generation projects within North Dakota and South Dakota that are either in-service, under construction, or committed through existing interconnection agreements with another 900 MW of additional generation currently under study through MISO’s interconnection process.

We have completed the construction of three major 345-kV switching stations along the Ellendale, North Dakota – Big Stone South, South Dakota – Brookings, South Dakota corridor during 2020 to allow for the reliable interconnection of over 1.1 gigawatts (GW) of new generation projects. These will not only interconnect low-cost generation resources onto the grid, but also allow for the strengthening of our existing transmission system throughout our service territory.

In addition to the new 345-kV transmission lines and switching stations, we are also in the process of performing upgrades to several of our existing transmission lines as a result of new renewables being added in our region. Within the past year, we have replaced numerous structures along the 230-kV system from Ellendale, North Dakota to Wahpeton, North Dakota. We have plans to reconductor the Ellendale, North Dakota – Oakes, North Dakota 230-kV line and the Oakes, North Dakota – Forman, North Dakota 230-kV line and replace structures to achieve increased clearances at higher loading levels. These upgrades will not only enhance transmission system capacity for additional regional generation, but will also improve transmission system reliability for customers within the region.

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