Generation interconnections

The size and location of new or expanded power plants can have significant impacts on the transmission system. These impacts are evaluated in MISO Definitive Planning Phase (DPP) process.  Information on the status, as of September 12, 2022, 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 footprint, 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 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. Additionally, 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 (2013 through 2022), nine new generators have gone into service and four uprates to existing generators have been completed, totaling approximately 1675 MW. These generators are included in Table PR-26. 

Table PR-26: Generator Requests From Past Ten Years Now In-Service

DateRequests on-lineMegawatts
3/4/2016J382 (RockGen Increase)48.3
4/27/2016J241 (Twin Falls Hydro uprate)3.7
5/1/2017J384 (Christiana uprate)21
5/8/2017J557 (Garden Corners solar)0.9
11/4/2017J395 (Quilt Block Wind Farm)98
3/31/2019J703 (Kuester)131.7
3/31/2019J704 (Mihm)56.5
10/28/2019J831 (Port Washington uprate)40
5/14/2020J390 & J760 (West Riverside)732
11/2/2020J886 (Two Creek Solar)150
9/13/2021J505 (Point Beach Solar Energy Center)100
12/1/2021J870 Badger Hollow 1150
1/7/2022J928 Garden Wind80

Table PR-27 lists the proposed generators in the generation queue for our service territory as of September 12, 2022 who have not yet signed the Generator Interconnection Agreement (GIA)It is important to keep in mind that the status of queued projects changes 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 11.3 GW. Of this proposed capacity, natural gas fired units reflect 0.1 percent, wind 8.2 percent, solar 62.4 percent, storage 25.8 percent, and hybrid 3.5 percent (see Figure PR-10). The hybrid units are combination of storage with wind or solar. Of the proposed capacity, 25.5 percent is in Zone 1, 3.8 percent is in Zone 2, 45.6 percent is in Zone 3, 20.6 percent is in Zone 4, and 4.4 percent is in Zone 5. 

Table PR-27: Proposed Projects Active in the Generation Queue as of September 12, 2022

ZoneQueue #CountyProject capacity (MW)Interconnection voltage (kV)Generator technology and fuel
1J1937Portage75345 Storage
1J1938Portage150345 Solar
2J1251Marquette, Mich.100138Solar
2J1750Marquette, Mich.149.7345Solar
2J1803Houghton, Mich.1.669Wind
2J1814Dickinson, Mich.22.5 138Solar
2J1817Houghton, Mich.2069Wind
2J2029Marquette, Mich.62.5138Solar
2J2316Dickinson, Mich.77.5138Solar
3J1773Iowa, Lafayette300345Wind
3J1781Iowa, Lafayette300345Wind
4J1253Fond du Lac100345Solar
4J1513Waupaca 300345Solar
4J1716Fond du Lac100345Solar
4J1994Fond du Lac97.088138Solar
Grand Total11,287

Table PR-28: Requests Previously in the Generation Queue Which Have been Withdrawn/Removed between June 1, 2019 and September 1, 2020

ZoneQueue #CountyProject Capacity (MW)Interconnection Voltage (kV)Generator Technology and FuelDeveloper Projected Commercial Operation DateDate Withdrawn
1J1719Waushara100138SolarSeptember 2023July 2021
1J2303Waushara100138SolarNovember 2024November 2021
1 Total200
2J849Delta125138SolarApril 2022April 2022
2J1244Houghton38.469WindSeptember 2021March 2022
2J1370Chippewa5069GasMarch 2021March 2022
2 Total213.4
3J1345Dodge2569StorageOctober 2021March 2022
3J1512Lafayette98.9138WindSeptember 2023July 2021
3J1720Columbia99138SolarMay 2024July 2021
3J1740Walworth100138SolarFebruary 2024July 2021
3J1928Grant100345StorageOctober 2025October 2021
3 Total422.9
4 Total0
5 Total0
Grand Total836.3

Table PR-29: Active Projects in the Generator Queue in Construction or Awaiting Construction as of September 21, 2021

ZoneQueue #CountyProject capacity (MW)Interconnection Voltage (kV)Generator technology and fuel
4J1101Manitowoc 20138Storage
Grand Total2,804
Includes projects with signed GIA.

Link to publicly posted MISO generation queue

Implications of generation development

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, 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

In Zone 1, about 25.5 percent (~2900 MW, Table PR-27) of the proposed generation is located near the 345-kV 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. In addition, the combination of proposed local generation in Wood and Portage Counties and generation west of ATC in Wisconsin and Minnesota, may be a driver for an additional 345-kV tie to the west if all the generation goes through. 

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. 

Three Zone 1 generator projects went in service or are in construction in the last five years. 

Zone 1 Generators In Construction or In Service

RequestSizeTypeCounty, StateStatus
J100299SolarWaushara County, Wis.In Construction
J732527.8Natural Gas - Combined CycleDouglas County, Wis.In Construction
J986150SolarWood County, Wis.In Construction
R1010115Natural GasMarathon County, Wis.In Construction
Zone 1 generators in construction or in service in the last 5 years.

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 generators. Since the Upper Peninsula transmission grid was primarily designed to serve local load, transmission upgrades may be required to accommodate these proposed plants.  

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 through the DPP process.  

The following table lists Zone 2 generator projects in service or in construction in the last five years. 

Zone 2 Generators In Construction or In Service

RequestSize (MW)TypeCounty, StateStatus
J5570.9SolarDelta County, Mich.In Service
J703131.7GasMarquette County, Mich.In Service
J70456.5GasBaraga County, Mich.In Service
J92880WindDelta County, Mich.In Service
J11831.4SolarDelta County, Mich.In Service
Zone 2 generators in construction or in service in the last five years.

Zone 3

In Zone 3, about 45 percent (~5000 MW, Table PR-27) of the active generation in the queue is at various locations throughout the zone. In recent cycles, there are more proposals in Dane and Columbia Counties and along the planned Cardinal-Hickory Creek Transmission Line Project corridor (especially in Iowa and Grant Counties). 

Along with the planned Cardinal-Hickory Creek Transmission Line Project, completion of the Badger Coulee Transmission Line Project and generation retirements seem to be the major drivers for new generator developments in those locations. 

Similarly, the southeast portion of Zone 3 continues to be an attractive location for siting generation. However, generation studies completed in the southwest corner of the state have demonstrated that siting 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 projects in service or in construction in the last five years. 

Zone 3 Generators In Construction or In Service

RequestSize (MW)TypeCounty, StateStatus
J38421GasDane County, Wis.In Service
J390/J760746.8GasRock County, Wis.In Service
J39598WindLafayette County, Wis.In Service
J100050SolarGrant County, Wis.In Construction
J100350SolarDodge County, Wis.In Construction
J1042180SolarWalworth County, Wis.In Construction
J115499.9WindMarathon County, Wis.In Construction
J118850SolarRock County, Wis.In Construction
J818149SolarJefferson County, Wis.In Construction
J850250SolarRock County, Wis.In Construction
J855100WindIowa County, Wis.In Construction
J86449.9SolarRichland County, Wis.In Construction
J870200SolarIowa County, Wis.150 MW In Service
J871100SolarIowa County, Wis.In Construction
J947200SolarGrant County, Wis.In Construction
Zone 3 generators in construction or in service in the last five years

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, it is unlikely that new generation will significantly alter the need for the major transmission reinforcements contemplated in that zone. In recent generation studies, more stress on the 138-kV path from North Appleton to South Fond Du Lac is observed and may need substantial reinforcements if the new generation projects move forward. This path is located west of Lake Winnebago and is parallel to 345-kV form North Appleton to South Fond Du Lac. 

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 some of these reinforcements. 

The following table lists Zone 4 generator projects in service or in construction in the last five years. 

Zone 4 Generators In Construction or In Service

RequestSize (MW)TypeCounty, StateStatus
J50599SolarManitowoc County, Wis.In Service
J886150SolarManitowoc County, Wis.In Service
J110120StorageManitowoc County, Wis.In Construction
J1153150SolarSheboygan County, Wis.In Construction
J1171100SolarDodge County, Wis.In Construction
Zone 4 generators in construction or in service in the last five years.

Zone 5

With the proposed development of Paris 345-kV Substation, Kenosha County is expected to get some reinforcement to the local transmission capacity and that may make it attractive for new generators to locate there. In the MISO and PJM generation studies, there seems to be a possible need for an additional 345-kV tie line between ATC and Common Wealth Eddison or local 345-kV reinforcement to handle regional flows driven by new generation and retirements. 

The following table lists Zone 5 generator projects in service or in construction in the last five years. 

RequestSizeTypeCounty, StateStatus
J83140GasOzaukee County, Wis.In Service
J878200SolarKenosha County, Wis.In Construction
S100560StorageKenosha County, Wis.In Construction