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ITC Transmission was founded in 1999 as International Transmission Co., a subsidiary of Detroit Edison (since renamed DTE Energy Electric Company, itself a subsidiary of DTE Energy), charged in the ownership, operation and maintenance of Detroit Edison's transmission system. In 2003, DTE sold the subsidiary to ITC Holdings Corp. In 2004, ITC Transmission became the first, fully independent electricity transmission company in the United States following the 2003 transfer of ownership from DTE Energy to ITC Transmission’s parent company, ITC Holdings Corp. ITC Transmission owns a fully regulated, high-voltage system that transmits electricity to local electricity distribution facilities. ITC Holdings Corp. (NYSE: ITC) became a publicly traded company in 2005 and is headquartered in Novi, Michigan. Today it owns transmission systems in several states under a unique independent business model.    
- 1 Electric grid systems of ITC Holdings Corp.
- 2 References
- 3 External link
Electric grid systems of ITC Holdings Corp.
The ITC Michigan system, covering much of Michigan's Lower Peninsula, is composed of transmission systems formerly owned by Consumers Energy and Detroit Edison.
The original ITC Transmission system
The original ITC Transmission system serves areas of southeastern Michigan and the Thumb region served by DTE Electric.
Largely overlapping DTE Electric's area, and launched on March 1, 2003, ITC's transmission line voltages are 345,000 volts, 230,000 volts, 138,000 volts, and 120,000 volts.
ITC has three 345 kV interconnections with First Energy Corporation in Ohio, via that company's Toledo Edison subsidiary (Bayshore-Monroe line, Majestic-Monroe-Allen Junction line, and the Majestic-Lemoyne line). Though owned by ITC these lines reside on towers designed and previously owned by Consumers, as they pass through part of their service area in southern Monroe and southeastern Lenawee Counties.
Currently, ITC Transmission is building a new 345 kV line, the "Michigan Thumb Loop", to strengthen the transmission grid in the Thumb Region to serve as a backbone for the interconnection of new generation sources in the area, including wind farms. This project is being built with steel tubular pylons in a double-circuit arrangement. This is scheduled for completion by 2015. 
ITC Transmission has 2,800 circuit miles of transmission lines, with 17,700 transmission pylons, and 171 stations and substations.  The system has 230 kV lines that cover the Metro Detroit area including Shelby Township in Macomb County where two meet at the Jewell Substation. The recognizable transmission line in the area is the so-called "Edison Corridor": two double-circuit 345 kV lines (portions of it become single circuit) and two 120 kV lines with one heading toward the northeast starting from the Bismark Substation to the Lenox Substation. This corridor extends 20 miles (32 km) through Warren from the Stephens Substation and through Sterling Heights and Utica, and finally Shelby and Washington Townships. ITC Transmission has spent approximately $1.2 billion in capital investments in rebuilding electric infrastructure in the metro-Detroit area since 2003. According to the 2012 SGS Statistical Services Transmission Reliability Benchmark Study, ITC Transmission was also ranked in the top 10% of electric utilities in terms of operational performance based on sustained outage performance data.
Michigan Electric Transmission Company (METC)
In October 2006, ITC Holdings Corp. completed the acquisition of METC, or Michigan Electric Transmission Company. Largely overlapping Consumers Energy's area, METC system uses line voltages of 345,000, 230,000 and 138,000 volts. Consumers retained its radial 138 kV lines. METC installed a 230 kV line running from Traverse City northeast to Kalkaska, Michigan particularly made of steel poles with three insulators or conductors, which was the first 230 kV transmission line in its system known as the Keystone to Clearwater 230 kV Line. Though the line was constructed for 230 kV operation, it remains operating at 138 kV until further upgrades are completed. METC has four 345 kV interconnections with American Electric Power, via AEP's Indiana Michigan Power division: Palisades-Cook #1, Palisades-Cook #2, Argenta-Robinson Park and Argenta-Twin Branch. METC has six other 138kV interconnections with other utilities: one 138kV interconnection each with Northern Indiana Public Service Company (Barton-Batavia line) and Alpena Power Company; two with the Cloverland Electric Cooperative (on former Edison Sault Electric Company facilities) in the eastern part of Michigan's Upper Peninsula (McGulpin-Straits #1 and McGulpin-Straits #2; these lines are submerged under the Straits of Mackinac); and two 138 kV interconnections with the Lansing Board of Water & Light (Davis-Oneida line and the Davis-Enterprise line). METC also completed capital projects including the 138 kV rebuild project near East Tawas, and the 138 kV Oakland-Tihart line.
METC includes 5,600 circuit miles of transmission lines, with 36,900 transmission towers and poles and 98 stations and substations across the majority of Michigan’s lower peninsula.  According to the 2012 SGS Statistical Services Transmission Reliability Benchmark Study, METC was ranked among the top 10% of electric utilities in terms of operational performance based on sustained outage performance data.
Interconnections between ITC Transmission and METC
There are four 345 kV interconnections between the ITC and METC systems to the west of DTE Electric's service area (Majestic-Tompkins line, Majestic-Battle Creek-Oneida line, Jewell-Thetford line, and the Pontiac-Hampton line), plus five 120/138 kV interconnections (the Custer-Whiting line, Genoa-Latson line, Hemphill-Hunters Creek line, Washtenaw-Lark-Blackstone line and the Atlanta-Thetford-Karn line). In addition, the Michigan Thumb Loop line that runs within the DTE service area will interconnect with Consumers / METC's Pontiac-Hampton line at a new substation in Tuscola County, northeast of Frankenmuth.
ITC Midwest LLC has transmission systems in portions of Iowa, Minnesota, Illinois and Missouri. This subsidiary was created on December 20, 2007 with ITC's acquisition of Interstate Power and Light Company's transmission system.  ITC Midwest owns and operates 6,600 circuit miles of transmission lines with 262 stations and substations.  Since 2008, ITC Midwest has completed 16 new generator interconnects, adding approximately 2,137 megawatts of wind energy production capacity to the grid. This additional amount is more than the total installed wind capacity that existed in Iowa in 2007.
ITC Great Plains
ITC Great Plains, a transmission-only utility, is a subsidiary of ITC Grid Development, LLC, which in turn is wholly owned by ITC Holdings Corp. ITC Great Plains became an independent transmission company member of the Southwest Power Pool (SPP) in September 2006. It is the only ITC Holdings operating company with a “greenfield” business model that is not predicated on acquiring other companies’ systems. ITC Great Plains has current operations in Kansas and Oklahoma.  
ITC Great Plains owns approximately 190 miles of transmission lines, with approximately 1,168 transmission towers and poles and 5 stations and substations. 
ITC Grid Development
Established in 2006, ITC Grid Development was created to explore new investment opportunities in the nation's transmission grid. This subsidiary is focused on partnering with local entities and utilities to improve electric reliability through infrastructure improvements and a creation of a regional transmission grid.
- Burr, M. T. (2010, Sept. 01). ITC Holdings: Riding the Wires. Retrieved from http://www.fortnightly.com/fortnightly/2010/09/itc-holdings-riding-wires?page=0,0
- Burr, M. T. (2005, July 01). Trancos reborn: Recent attrition raises the question. Retrieved from http://www.fortnightly.com/fortnightly/2005/07/transcos-reborn?page=0,8
- Equipment upgrades and preventive maintenance improve performance and reduce sf6 emissions. (2008, June 01). Retrieved from http://www.epa.gov/electricpower-sf6/documents/itc_casestudy.pdf
- Lum, R. (2013, Feb. 18). ITC Great Plains homes in on 3 SPP states for transmission investment - president. Retrieved from http://transmissionhub.com/2013/02/18/itc-great-plains-homes-in-on-3-spp-states-for-tran
- Dombek, C. (2013, Oct. 03). First phase of Michigan Thumb Loop project enters service. Retrieved from http://transmissionhub.com/pages/article_print.php?aid=2013/10/03/first-phase-of-michigan-thumb-loop-project-enters
- ITC Holdings corp. form 10-K, Filing Date: 2013-03-01. (2013, March 01). Retrieved from http://pdf.secdatabase.com/1373/0001445305-13-000406.pdf
- Federal Energy Regulatory Commission order granting in part and denying in part rate incentives, conditionally accepting tariff revisions, and establishing hearing and settlement procedures. (2009, March 16). Retrieved from http://www.ferc.gov/EventCalendar/Files/20090316185328-ER09-548-000.pdf