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ComEd To Expand 765 kV Wilton Center Substation Near Joliet, Illinois

Dec. 14, 2023
The expansion will support five wind farms and two solar farms to produce about 2,450 MW of renewable energy for the ComEd transmission system and the PJM energy market.

ComEd has announced an expansion of its 765 kV Wilton Center substation, a critical infrastructure investment that will enable the largest cluster of utility-scale onshore wind and solar projects interconnected to the Illinois electric grid to date and in the PJM energy market. The substation expansion is expected to be complete and proposed wind farms are expected to be operational in late 2026.

The Wilton Center substation, constructed in 1968 and located near Joliet, Illinois, supports ComEd’s highest voltage transmission lines of 765 kV, which are used for long-distance power transmission as they minimize the amount of power lost as electricity flows from one location to the next. The Wilton Center substation yard is approximately 1 million square feet and will expand by about 50% when construction is complete. Design engineering began in September, and work will include installation of new circuit breakers, transformers, relay switches, network data and control systems.

“The Wilton Center substation has been providing energy to our state and many others for over half a century, and with this expansion it will expand that capacity with fossil fuel-free power that will propel our grid into the future,” said Governor JB Pritzker. “The wind and solar farms supported by this substation expansion are another step in Illinois’ clean energy journey, a journey I’ve been grateful to undertake with ComEd.”

When complete, the substation expansion will support five wind farms and two solar farms with the capacity to produce a total of up to 2,450 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 ConnectGen, which will be the largest wind interconnection in northern Illinois and largest onshore wind project in the PJM territory. The project also includes 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 project that will also include 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.

The largest wind farm currently operating in Illinois is the 396 MW Twin Groves Wind Farm in McLean County. ComEd has 13 active wind projects underway in either construction or study phase, representing 3,120 MW of potential wind generation. Over the past 20 years, ComEd has interconnected more than 4,500 MW of wind generation to its transmission system. As of Nov. 1, 2023, distributed energy resources on the ComEd system, including residential, commercial, and industrial rooftop solar and community solar, increased by 148MW, representing about a 33% annualized growth rate.

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