Derby Junction to Ansonia 115-kV Transmission Line Rebuild Project

Derby Junction to Ansonia 115-kV Transmission Line Rebuild Project


About the project:

United Illuminating is Rebuilding the existing transmission lines within the 4.1-mile corridor between Derby Junction in Shelton, spanning the Housatonic River, and crossing portions of Derby and Ansonia, ending at the existing Ansonia Substation. The transmission lines presently consist of 34 double circuit lattice-type structures and 7 monopole structures. UI proposes to replace these structures with new double circuit steel monopoles to improve the reliability of the electric transmission system for customers in Connecticut and New England.

The existing transmission line structures were originally built in the early 1920s. Over the years, the transmission lines have been upgraded several times in response to increasing demand for electricity. Detailed engineering analyses and field inspections have determined that the lines now must be completely rebuilt to assure the continuation of reliable electric service.


Project Scope:

  • UI proposes to rebuild the transmission lines between Derby Junction and Ansonia Substation. These upgrades will require the following:
  • Perform engineering and environmental surveys along the transmission corridor
  • Prepare the corridor for construction (involving vegetation clearing and grading as necessary)
  • Construct approximately 40 new steel monopoles, along with new conductors, insulators, and hardware
  • Remove all existing transmission structures
  • Restore (regrade, seed) the areas affected by construction


Estimated Timetable (subject to change):

  • Permitting Approvals: 1st Quarter 2023
  • Construction: 2nd Quarter 2023
  • Completion/In-Service Date: 4th Quarter 2024


FAQs (upcoming)

Fact Sheet


If you have any questions regarding this project please call 888.848.3697 and reference the Derby Junction to Ansonia 115-kV Transmission Line Rebuild Project. A representative will return your call within three (3) business days. You may also email questions to


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