ComEd Livens Expanded High Voltage Substation at Wilton Center, Built to Enable Largest Cluster of Wind and Solar Projects in Illinois
Output from wind and solar farms to create up to 2,450 MW of clean energy
ComEd today announced it has livened an expansion of its 765 kilovolt (765 kV) Wilton Center substation in southern Will County. The substation expansion is a necessary upgrade to enable the largest cluster of utility-scale onshore wind and solar projects to be interconnected to the ComEd grid and in the PJM energy market starting in 2026.
"The livening of the Wilton Center expansion project marks a major milestone," said ComEd President and CEO Gil Quiniones. "The expansion will enable ComEd to deliver more than 2,000 megawatts of new renewable generation through our transmission system to meet growing demands for electricity among residential and business customers. What's more, interconnecting large volumes of renewable energy in the PJM zone helps us put downward pressure on rising energy costs."
The expansion increased the Wilton Center substation yard by 50% to 1.5 million square feet. The massive project was able to minimize environmental impact by reusing approximately 80,000 tons of topsoil from the site and using approximately 90,000 tons of on-site clay for the earthwork requirements, eliminating the need to export soil from or import it to the site and avoiding costly hauling of soil in and out of the project. New equipment includes 765kV circuit breakers, current and voltage transformers for instrumentation, disconnect switches, surge arresters, and extensive protection and control upgrades. A new detention pond was built to hold 2.8 million gallons of stormwater.
The Wilton Center substation, constructed in 1968 and located near Joliet, Ill., supports ComEd's highest voltage transmission lines of 765 kV, which are advantageous for moving large amounts of power over long distances as they minimize the amount of power lost as electricity flows from one location to the next. It is estimated that less than 1% of all existing transmission lines in the United States are built for this highest voltage level.
After an additional minor upgrade to the Wilton Center substation planned for the second quarter of 2026, ComEd's transmission system will have the capacity necessary for five wind farms and two solar farms to output a total of up to 2,450 megawatts (MW) of renewable energy for the ComEd transmission system and the PJM energy market, which includes all or parts of 13 states and the District of Columbia. The wind and solar farms to be supported by the expanded Wilton Center substation include:
- Heritage Prairie, a wind farm with up to 850 MW of generation capacity in western Kankakee County and northeastern Livingston County, developed by Pattern Energy and Repsol, which will be the largest wind interconnection in northern Illinois and largest onshore wind project in the PJM territory. The project includes an expansion of 300 MW of solar generation.
- Two wind farms developed by Panther Grove Wind Energy, each producing 400 MW of wind energy, one each in Livingston County and Woodford County.
- Lower Crossing Wind Farm in Kankakee County, which will produce 200 MW of wind energy and is being developed by owner Cordelio Power.
- Osagrove Flats Wind Farm in LaSalle County, a 150 MW wind project with a planned expansion of 150 MW of solar. It is being developed by Avangrid, Inc., whose Illinois projects include the 100 MW Midland Windfarm in Henry County, which was connected in November to the ComEd transmission system.
ComEd crews and Lindblad Construction led the construction work on the Wilton Center expansion while Burns & McDonnell served as ComEd's engineer for preliminary and final design and construction support.
ComEd is a unit of Chicago-based Exelon Corporation (NASDAQ:EXC), a Fortune 200 company and one of the nation's largest utility companies, serving more than 10.7 million electricity and natural gas customers. ComEd powers the lives of more than 4.2 million customers across northern Illinois, or 70 percent of the state's population. For more information, visit ComEd.com and connect with the company on Facebook, Instagram, LinkedIn, X and YouTube.
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