UI seeks permission to energize 115-kV transmission line upgrade project in Connecticut

United Illuminating (UI), in a Feb. 24 petition filed with the Connecticut Public Utilities Regulatory Authority (PURA), requested that PURA approve the manner and method of construction and provide permission to energize a 115-kV transmission line upgrade project.

The project consists of five interrelated segments and is located entirely within or directly adjacent to portions of the Metro-North Railroad (Metro-North) corridor that traverses the municipalities of Milford, Stratford and Bridgeport in Connecticut, the company said.

To date, four of the five project segments have been approved by the Connecticut Siting Council, and UI will submit the fifth segment for approval during 1Q17, the company said.

The project segments are:

  • The Milford 115-kV Transmission Line Upgrade Project
  • The estimated $22.3m Housatonic River Crossing
  • The estimated $1.9m Milvon Substation Take-Off Structure Replacement
  • The estimated $66.3m Baird Substation to Congress Substation
  • The estimated $69.1m Housatonic River Crossing to Baird Substation – UI expects to file with the council on or around March 31

Further discussing the 115-kV transmission line upgrade project, UI said that the transmission facilities that it would replace are supported on steel columns that are attached to Metro-North’s lattice catenary structures. Originally built in the early 1900s, some of the structures that make up Metro-North’s catenary system are more than 100 years old, UI said.

UI said that it began attaching its facilities to the Metro-North structures in the 1940s, and that it must now upgrade and replace those facilities in order to conform to code requirements, as well as to mitigate risks to the reliability of UI’s bulk transmission system.

UI would erect new steel structures and new conductors, and thereafter would de-energize the existing conductors and remove them from the Metro-North catenaries. The new structures would consist of galvanized tubular steel monopoles either within the Metro-North corridor or directly adjacent thereto, UI said.

The 115-kV transmission line sections are about six linear miles long, and constitute about 12 circuit miles, the company said. The lines consist of two three-phase circuits, with one circuit located on the northern edge of the Metro-North right of way, and the other one located on the southern edge. UI also noted that there are three electrical conductors per circuit – one conductor per phase – plus one fiber optic cable per circuit.

UI noted that it contracted with various suppliers and service providers for the project: General Cable Technologies of Highland Heights, Ky., supplied the 115-kV conductor; Prysmian S.p.A., of Milan, Italy, supplied the fiber optic cable; and M.D. Henry Co., of Pelham, Ala., supplied the steel structures. UI also said that McPhee Electric of Farmington, Ct., and Aldridge Electric of Libertyville, Ky., are its contractors tasked with performing substantially all of the construction.

The general sequence of events during construction is as such:

  • UI acquires the necessary property right as applicable
  • Aldridge would excavate and pour the foundations
  • McPhee would erect the steel structures and install the three-phase 115-kV conductor and fiber optic cable and tension the conductors
  • UI would de-energize the existing conductor and energize the new conductor
  • McPhee would remove the old conductors from the Metro-North catenaries

That sequence, UI added, is designed to maintain the reliability of the transmission system and minimize the necessity of planned outages.

The company said that following receipt of council approval, it started construction on certain portions of the project in the areas of Milford and Stratford. UI said that it plans to begin construction on the balance of the project on or around September 2018, and the company is scheduled to complete construction on or around April 2020, as well as to energize the entire project shortly thereafter.

Among other things, UI said that according to the construction schedule for the project segments, the Housatonic River Crossing is anticipated to be in service in August; the Baird Substation to Congress Substation is anticipated to be in service in March 2019; and the Housatonic River Crossing to Baird Substation is anticipated to be in service in April 2020.

UI is a subsidiary of AVANGRID (NYSE:AGR).

About Corina Rivera-Linares 3286 Articles
Corina Rivera-Linares was TransmissionHub’s chief editor until August 2021, as well as part of the team that established TransmissionHub in 2011. Before joining TransmissionHub, Corina covered renewable energy and environmental issues, as well as transmission, generation, regulation, legislation and ISO/RTO matters at SNL Financial from 2005 to 2011. She has also covered such topics as health, politics, and education for weekly newspapers and national magazines.