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 October 09, 2023, of generation requests in the 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 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 September 2023), 14 new generators have gone into service and five uprates or replacements to existing generators have been completed, totaling approximately 2050 MW. These generators are included in Table PR-26.
Table PR-26: Generator Requests From Past Ten Years Now In-Service
| Date | Requests on-line | Megawatts |
|---|---|---|
| 3/4/2016 | J382 (RockGen Increase) | 48.3 |
| 4/27/2016 | J241 (Twin Falls Hydro uprate) | 3.7 |
| 5/1/2017 | J384 (Christiana uprate) | 21 |
| 5/8/2017 | J557 (Garden Corners solar) | 0.9 |
| 11/4/2017 | J395 (Quilt Block Wind Farm) | 98 |
| 3/31/2019 | J703 (Kuester) | 131.7 |
| 3/31/2019 | J704 (Mihm) | 56.5 |
| 10/28/2019 | J831 (Port Washington uprate) | 40 |
| 5/14/2020 | J390 & J760 (West Riverside) | 732 |
| 11/2/2020 | J886 (Two Creek Solar) | 150 |
| 9/13/2021 | J505 (Point Beach Solar Energy Center) | 100 |
| 12/1/2021 | J870 Badger Hollow 1 | 150 |
| 1/7/2022 | J928 Garden Wind | 80 |
| 6/2/2022 | J1183 Garden Solar II | 1.35 |
| 10/17/2022 | J864 Bear Creek | 50 |
| 1/20/2023 | J1188 N Rock Solar | 50 |
| 1/20/2023 | J986 Wood County Solar | 150 |
| 4/4/2023 | J855 Red Barn | 92 |
| 7/27/2023 | R1010 Weston RICE | 133 |
| Total | 2048 |
Table PR-27 lists the proposed generators in the generation queue for our service territory as of October 09, 2023, 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 12.87 GW. Of this proposed capacity, natural gas fired units reflect 8.4 percent, wind 8.5 percent, solar 50.5 percent, storage 28.5 percent, and hybrid 4.1 percent (see Figure PR-10). The hybrid units are combination of storage with wind or solar. Of the proposed capacity, 39 percent is in Zone 1, 4 percent is in Zone 2, 32 percent is in Zone 3, 18 percent is in Zone 4, and 6 percent is in Zone 5.
[table “35” not found /][table “37” not found /]
[table “38” not found /]
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 39 percent (~5,036 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.
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. Furthermore, the new lines included MISO Long Range Transmission plan (LRTP) Tranche 1 will significantly strengthen this area.
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.
[table “28” not found /]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.
[table “29” not found /]Zone 3
In Zone 3, about 32 percent (~4161 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. Furthermore, the new line, terminating at Columbia 345-kV Substation, included MISO Long Range Transmission plan (LRTP) Tranche 1 will significantly strengthen the area.
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.
[table “31” not found /]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 from 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
| Request | Size (MW) | Type | County, State | Status |
|---|---|---|---|---|
| J505 | 99 | Solar | Manitowoc County, WI | In Service |
| J886 | 150 | Solar | Manitowoc County, WI | In Service |
| J1101 | 20 | Storage | Manitowoc County, WI | In Construction |
| J1153 | 150 | Solar | Sheboygan County, WI | In Construction |
| J1171 | 100 | Solar | Dodge County, WI | In Construction |
| J1253 | 100 | Solar | Fond du Lac, WI | In Construction |
| R1014 | 100.8 | Storage | Sheboygan, WI | In Construction |
| R1015 | 303.5 | Storage | Sheboygan, WI | In Construction |
Zone 5
With 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 Commonwealth Edison (ComEd) 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.
| Request | Size | Type | County, State | Status |
|---|---|---|---|---|
| J831 | 40 | Gas | Ozaukee County, WI | In Service |
| J878 | 200 | Solar | Kenosha County, WI | In Construction |
| J1316 | 50 | Storage | Kenosha County, WI | In Construction |
| S1005 | 60 | Storage | Kenosha County, WI | In Construction |