Duquesne Light Company on June 19 filed with the Pennsylvania Public Utility Commission a letter of notification for approval to upgrade an existing 138-kV ring bus scheme at the Montour substation in Robinson Township, Allegheny County, Pa., to a breaker-and-a-half bus scheme.
The company also said that it would upgrade associated structures, including new breakers, disconnects, relays, and control cables.
The project’s purpose is to enhance the reliability of the 138-kV transmission system and increase the reliability to 23-kV assets by modernizing the existing electrical infrastructure. The company added that the project is needed to enhance operability of the Montour substation, which was built in the mid-1950s. The upgrade to a breaker-and-a-half scheme under the proposed project allows Duquesne Light to isolate and/or remove any breaker for maintenance purposes without interrupting supply to the other circuits or transformers, the company said.
The company noted that the project – which involves relocating a total of about 0.49 miles of three separate transmission lines – also locates all of the control wiring in one new modernized control house to enhance efficiency of operations and maintenance at the substation.
The company said that the project would be executed in three phases:
* Phase I would reroute the Montour-Findlay (Z-45) 138-kV transmission line using temporary wood poles to enter the substation at an alternate location. This phase requires about four weeks of construction and must be completed in October
* Phase II prepares for reconfiguring the Crescent-Montour (Z-24) and Brunot Island-Montour (Z-44) 138-kV transmission lines by rerouting the Z-44 138-kV transmission line to enter the substation at an alternate location. This phase also includes installing temporary wood poles and three permanent monopoles to relocate the Z-24 138-kV transmission line such that it would enter the Montour substation at an alternative location. Those three permanent monopoles would also support the relocation of the Z-44 138-kV transmission line. Temporary wood poles would be used to allow the Z-44 138-kV transmission line to enter the substation at a temporary location until the project is completed. This phase requires about five weeks of construction and must be completed between October 2018 and September 2019
* Phase III transitions the Z-44 and Z-45 138-kV transmission lines from their temporary wood poles to their permanent monopoles. This phase requires about four weeks of construction and must be completed between March 1, 2020, and May 31, 2020
Further describing the project, the company noted that upgrading the ring bus scheme to a breaker-and-a-half scheme requires the company to expand the substation’s footprint, and consequently, relocate existing transmission lines entirely within the company’s existing fee interest. To relocate the existing lines, temporary transmission lines would be installed, Duquesne Light said, adding that the temporary lines would not extend outside of the company’s existing footprint. The temporary service lines are anticipated to be about 0.34 miles long, and would stay in place for nine to 19 months, the company noted.
The project affects about 0.49 total miles of existing transmission line: 0.19 miles of the Z-24 line; 0.19 miles of the Z-44 line; and 0.11 miles of the Z-45 line. The company added that upon completion, the final total length of all transmission lines would be decreased by about 0.06 miles.
The proposed substation reconfiguration and transmission line reroute eliminates one transmission tower, the company said, adding that it anticipates adding about five monopoles and 10 temporary wood poles over the course of the project.
Consistent with the reconfiguration, the company said that it proposes to build a new control house with new relay and control panels, replace the breakers, and upgrade and/or replace associated structures, disconnects, relays, control cables, and other associated facilities.
Among other things, the company said that it estimates the project would cost about $15.6m.