PPL’s (NYSE:PPL) PPL Electric Utilities on April 19 filed with the Pennsylvania Public Utility Commission a letter of notification to request approval to rebuild an approximately 6.4-mile section of existing double-circuit, 138-kV transmission line, which, the company said, would help ensure reasonably continuous and reliable service to customers located in Monroe County.
The line is located between a structure located just south of the PPL Electric Gilbert 138-12-kV substation located in Polk Township, Monroe County, and a structure located at the junction with the de-energized Little Gap 69-kV Transmission Tap to the PPL Electric Little Gap 69/12-kV substation located in Eldred Township, Monroe County (Gilbert-Little Gap Tap #1 and #2 138 kV Transmission Line).
The proposed project is needed to provide safe and reliable service into the future, the company added, noting that the existing transmission structures have reached an age and condition that the facilities must be replaced.
The company noted that the project is part of its Asset Optimization Strategy and involves rebuilding the lines to meet all current design and lightning protection standards.
Discussing the project’s need, the company said that the double-circuit Siegfried-Jackson #1 and #2 138-kV Transmission Line extends about 25 miles between the Siegfried 230/138/69-kV substation located in Whitehall Township, Northampton County, and the Jackson 138/69-kV substation located in Jackson Township, Monroe County. The entire double-circuit Siegfried-Jackson #1 and #2 138-kV Transmission Line serves these five 138/12-kV distribution substations, which serve a significant number of customers in Monroe County: Blue Mountain, Gilbert, Effort Mountain, McMichaels, and Appenzell.
The company also said that the double-circuit Gilbert-Little Gap Tap #1 and #2 1388-kV Transmission Line is a segment of the Siegfried-Jackson #1 and #2 138-kV Transmission Line that extends about 6.4 miles from the third structure south of the Gilbert 138/12-kV substation to its junction with the de-energized Little Gap 69-kV Transmission Tap. That portion of the transmission line primarily consists of 70 wood poles built around 1974 and 13 steel structures.
PPL Electric added that as part of its Asset Optimization Strategy, it has analyzed the double-circuit Gilbert-Little Gap Tap #1 and #2 138-kV Transmission Line and concluded that eight of the 13 steel structures have reached the end of their reliable service life. The company said that it has also determined that eight of the 13 steel structures need to be replaced in order to avoid engineering issues such as uplift, or the need to install additional mid-span poles, where no presently exist today, due to differences in structure height. The company noted that uplift occurs when an adjacent pole is higher, causing a force in the upward direction on either the pole or the conductor assemblies.
In addition, most of the “cellon treated” wood poles on the double-circuit Gilbert-Little Gap Tap #1 and #2 138-kV Transmission Line have reached the end of their reliable service life. The company added that since the installation of cellon treated wood poles in the 1970s, it has been discovered that cellon treated wood poles – which were discontinued in the 1980s – are susceptible to advanced aging through internal wood rot, insect infestation, and ultimately pole failure.
To resolve those issues with the aging facilities, PPL Electric said that it proposes to rebuild the 6.4-mile, double-circuit Gilbert-Little Gap Tap #1 and #2 138-kV Transmission Line, which would be rebuilt for double circuit, 138-kV operation. The 70 wood poles would be replaced with new steel monopoles, the company said, adding that a new dual optical ground wire (OPGW) would be installed along the 6.4-mile segment to provide lightning protection for the transmission lines and provide a communication path between the Gilbert 138-12-kV and Little Gap 69-12-kV substations.
PPL Electric said that it determined that no additional right of way (ROW) is required for the proposed rebuild of the double-circuit Jackson-Gilbert #1 and #2 138-kV Transmission Line, and as a result, the proposed project would be rebuilt entirely within the existing ROW.
Noting that the existing outdated structures range from about 45 feet to 105 feet in height, the company said that the new structures for the rebuilt Gilbert-Little Gilbert Tap #1 and #2 138-kV Transmission Line would have an average height of about 95 feet. However, impacts are anticipated to be minimal because average structure height is increasing by only about 10 feet and all new structures are anticipated to be placed within about 10 feet of the existing structures, the company said.
Among other things, the company said that while the proposed project would span seven wetlands and four streams, it is anticipated that the project would have no impacts on streams or wetlands because the entire project would be built within the existing ROW, and the new tower structures would be located to avoid impacts to wetland and streams.
The total estimated cost to design and build the project is $5.9m, the company said.
Subject to the commission’s approval, project construction is scheduled to begin in July to support an in-service date of July 2019, the company said.