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 June 1, 2012, of ATC’s portion of the Midwest Independent System Operator 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.

Per the Midwest ISO Revised Attachment X process, a generator interconnection study is usually performed in three stages: Interconnection Feasibility Study (Application Review Phase), Interconnection System Impact Study (System Planning and Analysis and/or Definitive Planning Phase), and an Interconnection Facilities Study (Definitive Planning Phase)

The Interconnection Feasibility Study includes a determination of thermal overload or voltage level impacts created by the new generator. This study process is performed by MISO approximately five to six times per calendar year and provides a qualitative screen of the affected facilities, indicating if there is ample capacity on the system to support the new interconnection. Depending on the results of the study, the request may either enter into the Definitive Planning Phase (DPP), System Planning and Analysis Phase (SPA) or Customer Not Ready Phase of the System Impact study.

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 Midwest ISO deliverability methodology, which determines whether a new generator is deliverable to the Midwest ISO 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 the Midwest ISO’s Module E Resource Adequacy procedures.

The Interconnection Facilities Study is conducted in the DPP process phase to specify and estimate the time and cost of the equipment, engineering, procurement and construction of the 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. These necessary changes to the transmission system are why we include in our Assessment models those proposed generators for which interconnection studies have been completed.

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 Generation Queue

Since ATC’s inception, twenty new generators have gone into service and four up rates to existing generators have been completed, totaling approximately 6000 MW. These generators are shown in Table PR-26.

Table PR-26

DateRequests on-lineMegawatts
6/14/01IC006 (Eden/Little Badger)31
2001G074 (Combined Locks)53
6/1/03G111 (Pulliam CT)85
6/1/03G148 (Petenwell/Big Pond)19.5
3/19/04G165 & G383 (Kewaunee uprate)43
6/1/04G225 (Kaukauna CT)60
6/15/04G035 & G072 (Riverside)655
5/1/05G096 & G160 (West Campus)150
6/1/05G044 (Fox Energy)602
6/2/05G103 (Sheboygan)370
7/1605, 9/1/06, 6/1/08G014 & G093 (Port Washington)
G510 (Port Washington increase)
4/1/07G240 (Manitowoc)54
5/07, 6/09G550 (Concord uprate)24
4/30/08G353 & G354 (Blue Sky Green Field)145
3/31/08G368 (Forward)129
6/26/08G144 (Weston Unit 4)550
12/11/08G507 & G507B (Cedar Ridge)68
3/16/09G338 (Butler Ridge)54
12/29/09, 1/12/11G051 (Oak Creek Units 1 and 2)1300
6/1/11G588 (Marshfield CT)59.7
6/22/11G833 & J023 (Point Beach Unit 2 uprate)59
12/31/11G706 & H012 (Glacier Hills)249
12/31/11G834/J022 (Point Beach)59
3/30/12J060 (Garden Wind)29
Former Generator Requests Now In-Service

Table PR-27 lists the proposed generators in the generation queue for our service territory as of June 1, 2012. 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 the queue is 902.2 MW. Of that proposed capacity, wind units reflect nearly 100 percent; less than 1 percent is comprised of hydro generation (see Figure PR-10). Of this generation, 0 percent in Zone 1, 28 percent in Zone 2, 39 percent is proposed in Zone 3, 33 percent in Zone 4, and 0 percent in Zone 5. Table PR-29 lists the required network upgrades associated with the generators shown in Table PR-27 with a signed Interconnection Agreement.

Table PR-27

ZoneQueue #CountyProject capacityInterconnection voltageGenerator technology and fuelDeveloper projected in-service date
1Total0 MW
2J061Delta70 MW138 kVwind turbine12/2013
2J066Chippewa60 MW69 kVwind turbine8/2011
2J119Chippewa61.2 MW69 kVwind turbine7/2012
2J147Chippewa60 MW69 kVwind turbine12/2013
2J241Dickinson4 MW69 kVhydro9/2015
2Total255.2 MW
3J084Grant50 MW69 kVwind turbine12/2015
3J109Lafayette99 MW138 kVwind turbine12/2012
3J134Dane150 MW138 kVwind turbine6/2013
3J217Columbia50 MW138 kVwind turbine12/2012
3Total349 MW
4G590Calumet98 MW138 kVwind turbine12/2010
4J094Manitowoc and Kewaunee200 MW138 or 345 kVwind turbine9/2012
4Total298 MW
5Total0 MW
Proposed Projects Active in the Generation Queue as of July 1, 2012

1. Suspended = Interconnection Agreement has been suspended by the customer.
2. TBD = Customer has lifted suspension and the new in-service date is to be determined.

Table PR-29

ZoneQueue #CountyProject capacityUpgrades
2J061Delta70 MW-Indian Lake-Hiawatha 138kV line energization.
-Mackinac HVDC Converter Station.
2J066Chippewa60 MW-New 69kV Interconnection Substation.
-Mackinac HVDC Converter Station.
-Pine River-Straits 69kV line rebuild
3J084Grant50 MW-New 69 kV Interconnection Substation.
-Communication Upgrades at Hillside and Nelson Dewey 69 kV Substations.
4G590Calumet98 MW-Expansion of Tecumseh Road Substation for Interconnection Substation.
-Thermal Upgrades at Melissa Substation.
Required Upgrades for Active Projects in the Generator Queue with a Signed Interconnection Agreement as of July 1, 2012

The developer’s projected in-service date listed in Table PR-27 is the last official commercial operation in-service date provided by the developer for that request. Under the Midwest ISO’s former Attachment X procedures, a developer may suspend their Interconnection Agreement which may delay the project and were not required to update their official in-service date as part of this suspension.

The following request has been suspended:

  • G590 – 98 MW wind farm, Line 971K91 in Calumet County, Wisconsin

Generation interconnection requests previously in the generation queue, which have been cancelled or removed from the queue since July 1, 2011 (because the developer withdrew the request or missed contractual milestones), are summarized in Table PR-28.

Table PR-28

ZoneQueue #CountySizeVoltageTypeIn-service date
3G282Lafayette99 MW138 kVwind turbine12/2010
3G749Lafayette50 MW69 kVwind turbine11/2012
3J116Dane999 MW345 kVwind turbine9/2013
4G427Fond du Lac98 MW345 kVwind turbine10/2013
4G611/G927Calumet100.5 MW138 kVwind turbine11/2012 suspended
Requests Previously in the Generation Queue Which Have been Withdrawn/Removed between July 1, 2011 and July 1, 2012

Link to publicly posted generation queue

Implications of generation development

Availability of fuel, water and transmission interconnections are among the key aspects to be considered when sighting 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 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 in the vicinity of 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 (>100 MW) 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 new 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 (up to 50 MW, 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 theLoopwould 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 new 345-kV lines which make up the GCMW corridor (GardnerPark– Highway 22, Morgan – Highway 22, and Highway 22 – Werner West). These additional lines significantly strengthen the Weston area, bringing much needed support to the area for both stability and thermal considerations for the new Weston 4 facility. A new generating facility was studied interconnecting 50 MW of biomass generation to the 115 kV transmission system located near the Weston substation. This study proved that properly sited generation of 50 MW or less can be accommodated to the transmission system in the area with minimal network upgrades. While the evaluation of new generation in this area is limited to this one study, it is possible that the GCMW corridor has the potential to support additional small to medium size generation development depending on actual physical location of the facility.

The infrastructure in the southern portion of Zone 1 consists of five 138-kV lines and several 69-kV lines. Only smaller generation projects (typically <25 MW) could be accommodated with minimal transmission reinforcements. The existing infrastructure in this portion of Zone 1 is not suitable for significant generation development.

The following table lists Zone 1 generator studies completed in the last five years.

Zone 1 Generator Studies

RequestSizeTypeCounty, StateStatus
G58855/60 MWCombustion TurbineWood County, WIIn-service
J04050 MWBiomassMarathon County, WIOut of Queue
Zone 1 generation studies completed in the last 5 years

Zone 2

We have completed studies of twelve generation interconnection requests for the Zone 2 area. Even though the first six requests are no longer active in the queue, they have helped us build a base of knowledge similar to what we have in other zones relating to likely generation interconnection impacts.

ATC has seen substantial interest in siting wind turbine generators in the Upper Peninsula of Michigan. One of the major challenges wind farms proposed for 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, substantial transmission upgrades area may be required to accommodate these proposed plants. The completion of the Northern Umbrella Plan, however, will result in a much more robust 138-kV network at Plains Substation that could accommodate medium sized generation in the future at or near Plains.

It is likely that given the scarcity of 138-kV infrastructure in the Upper Peninsula there are very few locations in Zone 2 that are ideal candidates for significant generation development. Generation studies have indicated substantial re-enforcements are required to accommodate small to medium size generation development throughout the Upper Peninsula. 

There are areas in Zone 2, such as on the western end of theUpper Peninsula, which are or will be in need of transmission reinforcements where smaller generation projects could be beneficial in terms of deferring transmission expenditures. The allowable capacity of such generation would depend on the location. However, other potential impacts (stability, fault duties) would need to be evaluated on a location-by-location basis.

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

Zone 2 Generator Studies

RequestSizeTypeCounty, StateStatus
G567-568165 or 300 MWCoalDelta County, MIOut of Queue
G58319 MWBiomassOntonagon County, MIOut of Queue
G750201 MWWindMarquette County, MIOut of Queue
G799120 MWWindHoughton County, MIOut of Queue
G93729 MWWindDelta County, MIOut of Queue
J03950 MWBiomassDelta County, MIOut of Queue
J06029 MWWindDelta County, MIIn Queue
J06170 MWWindDelta County, MIIn Queue
J06660 MWWindChippewa County, MIIn Queue
J07826 MWBiomassMarquette County, MIOut of Queue
J11961.2 MWWindChippewa County, MIIn Queue
J14760 MWWindChippewa County, MIIn Queue
Zone 2 generation studies completed in the last 5 years

Zone 3

In Zone 3, generation has been proposed in various locations, but over half have been in the southern-most counties in Zone 3. 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 (< 100 MW) 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.

Zone 3 Generator Studies

RequestSizeTypeCounty, StateStatus
G28299 MWWindLafayette County, WIIn Queue
G36680 MWWindColumbia County, WIOut of Queue
G527280 MWCoalGrant County, WIOut of Queue
G546100 MWWindWalworth County, WIOut of Queue
G55024 MWSimple cycleJefferson County, WIIn Service
G553280 MWCoalColumbia County, WIOut of Queue
G70699 MWWindColumbia County, WIIn Queue
G72499 MWWindDane County, WIOut of Queue
G74799 MWWindRock County, WIOut of Queue
G74950 MWWindLafayette County, WIIn Queue
G793100 MWWindRock County, WIOut of Queue
G901600 MWWindWinnebago County, WIOut of Queue
G902600 MWWindWinnebago County, WIOut of Queue
G95349.5 MWWindGrant County, WIOut of Queue
G95449.5 MWWindGrant County, WIOut of Queue
H012150 MWWindColumbia County, WIIn Queue
H02448 MWWindColumbia County, WIOut of Queue
J08450 MWWindGrant County, WIIn Queue
J134150 MWWindDane County, WIIn Queue
J21750 MWWindColumbia County, WIIn Queue
Zone 3 generation studies completed in the last 5 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, however, it is unlikely that new generation in Zone 4 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 inDoorCounty, provided such generation is small-scale (< 50 MW) 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 inDoorCountyis projected to precipitate the need for reinforcements in the future. Small-scale generation potentially could defer certain of these reinforcements.

One area in Zone 4 that cannot accommodate any additional generation without significant transmission reinforcements is the area around thePointBeachand Kewaunee nuclear plants. In this area, existing transmission lines have little excess capacity and the existing generation requests have demonstrated that large scale transmission projects are needed for even modest increases in existing generation capacity. As the system evolves, stability margins at those plants may become a concern even with the transmission improvements. Siting of additional generation in the area will require extensive studies to ensure that system reliability will continue to be met for the existing generators in the area.

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

Zone 4 Generator Studies

RequestSizeTypeCounty, StateStatus
G42798 MWWindFond du Lac County, WIIn Queue
G50768 MWWindFond du Lac County, WIIn Service
G59098 MWWindCalumet County, WIIn Queue
G61199 MWWindCalumet County, WIIn Queue
G773150 MWWindBrown County, WIOut of Queue
G833/J02359 MWNuclearManitowoc County, WIIn Service
G834/J02259 MWNuclearManitowoc County, WIIn Queue
G9271.5 MWWindCalumet County, WIIn Queue
G987400 MWWindBrown County, WIOut of Queue
J094200 MWWindManitowoc County, WIIn Queue
Zone 4 generation studies completed in the last 5 years

Zone 5

Two major generation additions have been completed for Zone 5. The first addition is at Port Washington Power Plant, which was completed in June of 2008. In order to accommodate the two blocks of generation at Port Washington, the two Port Washington–Rangeline 138-kV lines and the three Port Washington–Saukville 138-kV lines were rebuilt in 2005 and the Saukville–Pleasant Valley–Arthur Road–St. Lawrence 138-kV line was rebuilt in 2007 at a cost of approximately $10 million.

The other site for new generation is the Oak Creek Power Plant. The PSCW approved two new units at the Oak Creek Power Plant, with the first unit having gone into service in December of 2009 and the second unit achieving commercial service 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 345-kV 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.

No Zone 5 generator studies have been completed in the last five years.