Following a detailed aerial inspection by Haverfield Aviation, Public Service of New Hampshire (PSNH) determined there was a need for maintenance on a stretch of line across the Piscataqua River from Portsmouth, New Hampshire, U.S., to South Eliot, Maine, U.S. The utility concluded that although the lines were in good shape (having been installed in the early 1970s), age and wear of numerous components had created possible safety hazards.
Dubbed the Schiller Project, the plan required the replacement of insulators on two 350-ft (107-m) towers and vibration dampers on 1,750 ft (533 m) of line energized with 345 kV.
Completing the project through the conventional method of ground-based crews climbing the towers would have been time-consuming and labor-intensive. Factoring in the additional complexities involved with de-energizing the line and supplying alternative sources of electricity for customers during the work resulted in a project completion estimate of one to four months, depending on factors such as weather.
However, a proposal from Haverfield Aviation, using the company's live-line maintenance product and its Specialized Services Team, determined that the project could be completed more quickly and at a fraction of the cost using aerial services.
“Haverfield crews were in here doing live-line work. The benefit that brings is that we don't have to send crews up there to do the mechanical work, which would be very, very tedious and labor-intensive by going up there with ladders and ropes,” said Gary Booth, project leader for PSNH.
The helicopter takes the crew and equipment right to the top of the structure, so they are right there where the work needs to be done, thus reducing the time it takes to accomplish the work.
The intricacies of the double-circuit line, single wire with a double-insulator string posed several challenges. A specialized aerial spacer cart and a uniquely engineered winch to run through sheave blocks were fabricated specifically for the project. A helicopter was used to “long line” a two-man crew and the specialized equipment to the towers where the insulators were replaced. The spacer cart was used to trolley along the line to replace the dampeners.
Originally estimated to take eight to 10 days, the project was completed in five days at a cost savings of approximately 35% compared to conventional methods.
To view a video of the aerial work, visit www.haverfield.com.