Generation interconnections

The size and location of new or expanded power plants can have significant impacts on the transmission system. These impacts can range from very positive (adding voltage support in a weak area of the system) to very negative (aggravating loading problems and/or causing generator instability). Information on the status, as of September 1, 2020, of generation requests in the American Transmission Co. (ATC) portion of the MISO generation interconnection queue is provided in this section. There continues to be significant activity in ATC’s portion of this queue, ranging from newly proposed generation projects to cancellation of previously proposed generation projects. 

There are two key aspects in determining the total impacts a proposed new generator may have on the transmission system: 

  • impacts of interconnecting the new generator to the transmission system and 
  • impacts of using the transmission system to deliver power from the new generator. 

As described in MISO’s Attachment X process, a generator interconnection study is usually performed in three phases which are all within the Definitive Planning Phase (DPP): an Interconnection System Impact Study (Phase 1, 2 and 3), and an Interconnection Customer Interconnection Facilities Study (Phase 2 and 3). The Network Upgrade Facilities Study begins after the System Impact Study is completed in Phase 3. 

The Interconnection System Impact Study includes a determination of whether the proposed generator and other nearby generators will remain connected to the system under various disturbance situations, such as line trips and equipment failures and includes a fault duty analysis to determine whether existing system equipment can accommodate the increased short circuit fault duty caused by the new generator. Finally, the System Impact Study will identify solutions for any thermal, stability or fault duty deficiencies. 

Delivery impacts are assessed during the DPP portion of the interconnection study process using the MISO deliverability methodology, which determines whether the output of a new generator is deliverable to the MISO energy market and to what percent if not wholly deliverable. Whatever portion of the new generator that is deliverable may then be used as a Network Resource by Network Customers through MISO’s Module E Resource Adequacy procedures. 

The Interconnection Customer Interconnection Facilities Study is conducted in Phase 2 and 3.  It specifies and estimates the time and cost of the equipment, engineering, procurement, and construction of the interconnection facility upgrades identified in the earlier interconnection studies. 

The Network Upgrade Facilities Study is conducted after Phase 3. It specifies and estimates the time and cost of the equipment, engineering, procurement and construction of the network system upgrades identified in the earlier interconnection studies. 

The results of the interconnection studies are needed to develop a comprehensive picture of the transmission facilities that will be required for a proposed generator. Only transmission facilities that result from generators with a signed Interconnection Agreement are included in the 10-Year Assessment models. 

The first portion of this section provides the status of the generation queue within our service territory. The second portion of this section describes the transmission system additions associated with various proposed generation projects for which final interconnection studies have been completed. The third portion of this section describes some of the implications associated with interconnecting generation at various locations within our service territory. 

ATC Portion of MISO Generation Queue

Over the last ten years, nine new generators have gone into service and six uprates to existing generators have been completed, totaling approximately 2,900 MW. These generators are included in Table PR-26. 

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Table PR-27 lists the proposed generators in the generation queue for our service territory as of September 1, 2020. It is important to keep in mind that the status of queued projects changes fairly often as projects enter and withdraw from the queue, sign generator interconnection agreements and start construction. This table lists each proposed generation project and summarizes them by zone and MW amount. These proposed projects also are shown by approximate location in Figure PR-9.

As shown, the total capacity of proposed generators in this portion of the queue is roughly 8,625 MW. Of this proposed capacity, natural gas fired units reflect 4.4 percent, wind units reflect 14.7 percent, solar 77.2 percent, and storage is 3.7 percent (see Figure PR-10). Of the proposed capacity, 19.1 percent is in Zone 1, 6.9 percent is in Zone 2, 57.3 percent is in Zone 3, 15.0 percent is in Zone 4, and 1.7 percent is in Zone 5. Table PR-29 lists the required network upgrades associated with generators with a signed Interconnection Agreement. 

Table PR-27: Proposed Projects Active in the Generation Queue as of September 1, 2020

ZoneQueue #CountyProject capacity (MW)Interconnection voltage (kV)Generator technology and fuelDeveloper projected in-service date
1J1253Fond du Lac100138Solar8/1/2021
2J1183Delta, Mich.1.35138Solar1/31/2019
2J1244Houghton, Mich.38.469Wind9/15/2021
2J1251Marquette, Mich.100138Solar10/30/2022
2J1252Marquette, Mich.20138Storage10/30/2022
2J1370Chippewa, Mich.5069Natural gas - simple cycle3/1/2021
2J1750Marquette, Mich.149.7345Solar8/1/2023
2J1762Iron, Mich.22.569Solar9/15/2023
2J1792Houghton, Mich.22.569Solar9/15/2023
2J1803Houghton, Mich.1.669Wind9/15/2021
2J1809Houghton, Mich.62.5138Solar8/15/2023
2J1814Dickinson, Mich.22.5 138Solar9/15/2023
2J1817Houghton, Mich.4069Wind9/15/2021
2J1823Houghton, Mich.62.569Solar9/15/2023
3J1773Iowa, Lafayette300345Wind4/15/2024
3J1781Iowa, Lafayette300345Wind4/15/2024
3J1838Dane320138Natural Gas - Combined Cycle2/12/2025
3J1843Dane12138Natural Gas - Simple Cycle3/15/2023
4J1513Waupaca 300345Solar10//1/2023
4J1716Fond du Lac100345Solar8/1/2022
Grand Total8624.65
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Table PR-29: Required Upgrades for Active Projects in the Generator Queue in Construction as of September 1, 2020

ZoneQueue #CountyProject capacity (MW)Upgrades
1J732Douglas527.8New 345 kV "Superior" Substation; Scel Stone Lake 345/161 kV, Transformer Replacement
1J821Marathon99.9New 115 kV "Zenith" Substation
2J849Delta, MI125Grounding Grid
2J928Delta, MI80CT Replacement, Grounding Grid
3J850Rock250New 138 kV "North Creek" Substation; Bristol - Elkhorn 138 kV, Uprate; North Lake Geneva Tap - Burlington 138 kV, Uprate; Bass Creek - Townline Rd. 138 kV, Reconductor; New "East Paris" 345 kV Substation; New East Paris/Paris 345/138 kV Transformer
3J864Richland49.9Highland - Eden 69 kV, Uprate
3J870Iowa200New 138 kV "Highland Substation"; Highland - Eden 69 kV, Uprate; Highland - Spring Green 69 kV, Uprate; Eden - Lands End 69 kV, loop into Highland
3J871Iowa100New 138 kV "Highland Substation"; Highland - Eden 69 kV, Uprate; Highland - Spring Green 69 kV, Uprate; Highland - Eden - Lands End 69 kV, loop into the Highland
3J855Iowa100New 138-kV "Ebenezer" Substation
3J818Jefferson149Concord - Cooney 138 kV, Reconductor
3J947Grant200New 138 kV "Tennyson" Substation, Hillman SS, upgrade 138/69 kV transformer, uprate, Rock River SS, bus switch upgrade
3J584Green60New 69 kV "Jordan Rd" Substation
3J807Lafayette41.1North Monroe - Bass Creek 138 kV, uprate, Darlington - North Monroe uprate, Rock River SS bus switch upgrade, Elkhorn - North Lake Geneva 138 kV uprate, Hillman SS upgrade transformer, Rock River SS terminal upgrade
3J819Lafayette99.9North Monroe - Bass Creek 138 kV uprate, Darlington - North Monroe uprate, Rock River SS bus switch upgrade, Elkhorn - North Lake Geneva 138 kV uprate, Hillman SS upgrade transformer, Rock River SS terminal upgrade, South Monroe - Browntown (Y-155) 69 kV rebuild
4J505Manitowoc 99New 138 kV "Apollo" Substation
5J878Kenosha200New "East Paris" 345 kV Substation; New East Paris/Paris 345/138 kV

Link to publicly posted MISO generation queue

Implications of generation development

Availability of fuel, water, land and transmission interconnections are among the key aspects to be considered when siting generation. 

From a transmission perspective, the ability of the transmission system to accommodate new generation is a function of stability, power flow and short circuit analyses. For certain generation technologies, harmonics, fast control interactions and voltage fluctuations may need to be considered as well. In most instances, new generation will require certain transmission system reinforcements to interconnect and deliver the generation output. In a few specific instances, new generation can be beneficial to the transmission system, perhaps even deferring or eliminating the need for transmission reinforcements that would be necessary absent the new generation. The ability of generation to defer or eliminate the need for transmission reinforcements also can be a function of the generation location, number of generators, and/or expected generator capacity factor. 

In this section, a general zone-by-zone evaluation of the likelihood of needing or deferring transmission reinforcements for various generator locations is provided. The purpose of these evaluations is to provide a cursory indication to the generation market of the likely magnitude of the impact and the transmission reinforcements that would likely be needed by general location. 

Zone 1

Within Zone 1, generation has been proposed in various locations, and most of the proposals have involved generation located near the 345kV infrastructure. Based on studies that we have conducted for proposed generation interconnections to date some transmission reinforcements are likely to be required for any significant generation development. The extent and nature of the reinforcements largely would be a function of where the power from the generation is to be delivered. 

The reliability of the northern portion of Zone 1, the Rhinelander Loop, has been significantly improved with the completion of the Cranberry to Conover 115 kV line and the Conover to Plains 138 kV conversion. While no new generator requests have been studied for this area, the addition of the Rhinelander Loop improvement projects may be able to support small-sized (depending on location) generation development, provided generator stability can be maintained, and provided it can be located in the northern portion of the Loop. Whether this generation would be cost-effective as a transmission-deferral mechanism would depend on a number of factors. The need for additional stability and thermal reinforcements in and outside of the Loop would be a function of where the new generation is sited and where the power is to be delivered. These improvements will be required to ensure that NERC reliability standards are continuously being met and that the security of the Rhinelander loop is not compromised. 

The transmission infrastructure in the central portion of Zone 1 includes three 345 kV lines (Gardner Park – Highway 22, Morgan – Highway 22, and Highway 22 – Werner West). These lines significantly strengthen the Weston area, bringing much needed support to the area for both stability and thermal considerations. 

The infrastructure in the southern portion of Zone 1 consists of several 69 kV and 138 kV lines. The existing infrastructure in this portion of Zone 1 is not suitable for significant generation development. 

Two Zone 1 generator studies have been completed in the last five years. 

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Zone 2

ATC has seen substantial interest in siting generators in the Upper Peninsula of Michigan. One of the major challenges proposed generation in the Upper Peninsula will face is the limited transmission infrastructure to interconnect and deliver the energy produced by these power plants. Since the Upper Peninsula transmission grid was primarily designed to serve local load, transmission upgrades may be required to accommodate these proposed plants. Completion of the Northern Umbrella Plan and the ATC Energy Collaborative-Michigan projects have improved this infrastructure. ATC is also working with MISO and particularly our Michigan stakeholders to identify appropriate solutions to potential generation retirements. 

There are areas in Zone 2, which currently or will eventually need transmission reinforcements where smaller generation projects could be beneficial in terms of deferring transmission expenditures. The allowable capacity and potential impacts of such generation would depend on location. Impacts like thermal, stability and fault duties would need to be evaluated.  

The following table lists Zone 2 generator studies completed in the last five years. 

Zone 2 Generator Studies

RequestSize (MW)TypeCounty, StateStatus
J394327GasMarquette County, Mich.Out of Queue
J5570.9SolarDelta County, Mich.In Service
J703131.7GasMarquette County, Mich.In Service
J70456.5GasBaraga County, Mich.In Service
J711130WindBaraga County, Mich.Out of Queue
J849125SolarDelta County, Mich.In Construction
J92880WindDelta County, Mich.In Construction
Zone 2 generation studies completed in the last 5 years

Zone 3

In Zone 3, generation has been proposed in various locations. Generation could be beneficial in a few areas depending on the capacity of such generation and the exact location. 

Even with the on-going reinforcement plans for Dane County, smaller-scale generation in certain locations could be beneficial to improving the voltage profile in the area and potentially deferring transmission reinforcements. Stability analysis would need to be conducted to ensure stable operation of such generation. 

Similarly, the southeast portion of Zone 3 is heavily loaded and will require transmission reinforcements in the future to ensure reliable operation. Small-scale generation in certain locations could be beneficial to changing power flow patterns and improving the voltage profile in the area. Generation studies completed in the southwest corner of the state have demonstrated that sighting large amounts of generation in rural areas may require substantial upgrades to the transmission system to ensure reliable operation. 

The following table lists Zone 3 generator studies completed in the last five years. 

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Zone 4

Generation has been proposed in various locations in Zone 4. Generation could be beneficial in a few areas depending on the capacity of such generation and exact location. Given the nature of the issues in Zone 4, however, it is unlikely that new generation will significantly alter the need for the major transmission reinforcements contemplated in that zone. 

One area where generation could defer the need for transmission reinforcements is in Door County, provided such generation is small-scale and appropriately located. Currently, the northern portion of the county is served radially, and electric service is subject to interruption for the loss of the single 69 kV line serving the area. The voltage profile in Door County is projected to precipitate the need for reinforcements in the future. Small-scale generation potentially could defer certain of these reinforcements. 

The following table lists Zone 4 generator studies completed in the last five years. 

Zone 4 Generator Studies

RequestSize (MW)TypeCounty, StateStatus
J293475Natural GasOutagamie County, Wis.Out of Queue
J50599SolarManitowoc County, Wis.In Construction
J886150SolarManitowoc County, Wis.In Construction
Zone 4 generation studies completed in the last 5 years

Zone 5

One major generation addition has been completed within the last ten years for Zone 5. The site of this generation is the Oak Creek Power Plant. The first unit achieved Commercial Operation in December of 2009 and the second unit achieved Commercial Operation in January of 2011. 

Studies of other proposed generation projects that are no longer in the generation queue indicate that additional generation in certain areas of Zone 5 would pose stability problems. In particular, larger-scale generation interconnecting to the 345kV network could pose stability issues. 

Smaller-scale generation in certain locations in Washington and Waukesha counties potentially could be accommodated without the need for transmission reinforcements if located appropriately. 

One Zone generator study has been completed in the last five years. 

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