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Bethel to Norwalk Transmission Line Fiber Optic System

This ambitious project was undertaken to save Connecticut consumers millions of dollars in congestion costs while making the regional transmission grid more reliable, secure and efficient. Sertex furnished and installed approximately 44 miles of underground fiber optic cable used for relay and protection of a newly installed 345-kV electric transmission line. The system included connections at seven substations along the route. The fast-track project schedule required Sertex to complete the system within a narrow time frame to support in-service testing and ensure the overall project schedule was met.

The new 345-kV line includes 8.5 miles of new overhead construction and 11.8 miles of 345-kV underground cables. Northeast Utilities (NU) specified 345-kV high pressure fluid-filled (HPFF) cable systems for the majority of the underground portion of the route of the new 345-kV line, and 2.1 miles of 345-kV cross-linked polyethylene (XLPE) cables. At Plumtree Substation in Bethel, NU specified a state-of-the-art 345-kV outdoor gas-insulated substation (GIS), because the space for expansion was severely constrained by adjacent wetlands.

At the Norwalk Substation, we installed an indoor 345-kV GIS system, autotransformers, three underground 115-kV line sections, a fourth 115-kV switchyard bay, and a 345-kV line terminal structure. In addition, 345-kV line transition stations were constructed in the towns of Bethel, Redding and Wilton at points where the 345-kV line transitions from overhead to underground construction.