Niagara Mohawk Power d/b/a National Grid USA is proposing to increase ground clearances of the conductors at 12 locations on the T1260 Gardenville-Dunkirk #141 115-kV transmission line where clearances are substandard relative to the National Electrical Safety Code (NESC).
Timely completion of the work is essential to mitigate potential impacts to customer reliability and public safety, the company added in its Part 102 Report filed with New York state regulators on Jan. 29.
National Grid also noted that it has not yet completed its assessment to determine which locations are actually substandard, nor has it completed a final plan to mitigate those that are, but because of the time-sensitive nature of the project, it is submitting the report based on preliminary information.
The company noted that it anticipates that the number of locations where clearances must be increased will remain the same or decrease as its assessment is finalized. The assessment is scheduled to be finalized on March 27.
The approximately 45-mile line is located between the old Gardenville substation in West Seneca, N.Y., and the Dunkirk substation in Dunkirk, N.Y., and traverses the towns of West Seneca, Lackawanna, Hamburg, Village of Angola, Town of Brant, and the Village of Farnham in Erie County, N.Y., and the Village of Silver Creek and towns of Hanover, Sheridan and Dunkirk in Chautauqua County, N.Y.
The line, which was built in the 1930s, is carried, along with the Gardenville-Dunkirk #142 115-kV line on double circuit flexible steel structures, square based lattice towers and some single/double wood pole structures.
The project is needed to provide for public safety and system reliability by conforming clearances to the NESC, the company added, noting that line has been identified as having 12 locations where work is required to increase clearance of the conductors above the ground. There are also six tap lines from the line to the substations.
It should be noted, National Grid added, that separate from this project, a more extensive refurbishment of the #141 and #142 lines is planned within the next three years, as well as a conductor clearance review of the #142 line. The refurbishment scope includes replacing deteriorated structures, foundations, tower members, insulators, shieldwire and other hardware on those lines.
Two of the three new intermediate structures proposed for installation under the project are being installed to correct the immediate conductor clearance problems, but those two locations will be studied in greater detail under the upcoming asset refurbishment project and both structures are expected to be temporary until the asset refurbishment project is completed.
The majority of the project activities will take place within the existing managed right-of-way (ROW), which is a combination of fee and easement property rights currently held by National Grid, the company added. However, the proposed location of temporary new structure 320A is within CSX Railroad ROW and a licensing agreement application as well as associated fee has been submitted to CSX. Permission to build is pending CSX internal review, the company added.
National Grid said there are no long-term impacts on agricultural land associated as a result of the project. All work in agricultural areas will be conducted under best management practices in order to minimize the impact to such lands and will be restored to existing contours.
Among other things, National Grid noted that an advantage-disadvantage analysis has been developed for the project. Such an analysis provides a framework by which the features or facts that support one or another mode of construction can be identified clearly, specifically underground versus overhead construction of a transmission line.
Placing a short section of an overhead transmission line underground is often referred to as installing a “dip” in the line, the company said, adding that the cost for installing a dip in a small portion of the #141 line between two structures would cost between $3m and $4.6m, depending on the route selected. That would represent a significant increase in cost over the proposed overhead project, estimated to be about $0.1m per pole installation or replacement, and would introduce significant operating disadvantages to the transmission system.
Major operational issues associated with a short dip include lengthy outage repair times, the company added.
National Grid is a subsidiary of National Grid plc.