by Jen Neville
If your job is to maintain transmission lines, then what would you do when you have to replace insulators and spacer dampers on a line that crosses steep mountains and extends down into orchard-filled valleys? What if there is only limited time to take lines out of service for repair, as the continuous flow of power is expected to remain uninterrupted.
During the past four years, Sierra Nevada’s line crews have been perfecting the solution to this complex question: using live-line and de-energized maintenance techniques with a helicopter. “It all started in baby steps,” explained SN Foreman III Brian Adams. “Our first project was a fiber optic project. We used the helicopter to fly material to the guys so they could clip in the new overhead fiber optic ground wire. But our linemen still had to climb the towers.” That was the pilot effort in 2009. Since then, Western’s SN crews have completed extensive training and developed a new maintenance program with its own manual to integrate helicopters as another tool for getting the job done.
This summer, with the program fully integrated, linemen grabbed a ride in the helicopter to work from the long line to perform mid-span work or land on a tower to perform work there. “We are going to be performing our first-ever 230-kilovolt insulator change out hot with a helicopter,” said SN lineman Ryan Mumma.
Here is a glimpse into the projects this integrated process has helped or will help in California this summer:
|Replace spacer dampers (about 80 line miles total)
Olinda-to-Tracy 500-kV line
Captain Jack-to-Olinda 500-kV line
|Routine maintenance to ensure space between conductor phases is retained.
||Fly lineman and spacer cart to line using long-line method. Lineman situates spacer cart on line and gets in. Change out spacers. When switching to a new line span, helicopter picks up and moves the spacer cart and lineman to the next section. (Energized line)|
|Replace insulators (more than 900)
Olinda-to-Tracy 500-kV line (de-energized)
Trinity-to-Carr 230-kV line (energized)
Malin-to-Round Mountain 230-kV line (de-energized)
|Old porcelain insulators are passed their life span or are showing cracks from wear and weather.
||Fly linemen to structures. Unhook and carry off old insulator string using helicopter and long-line and bare-hand methods and then fly in new insulator string for installation. (One line energized, two others de-energized)|
|Install 280 goat head peaks
||Cottonwood-to-Roseville 230-kV line
||Support needed fiber optics.
||Fly linemen to the top of the structure. Pick up and fly goat peak to be bolted on top of the structure. (Energized line)|
|Replace 66 marker balls
||Captain Jack-to-Olinda 500-kV line
||Worn by weather and in poor condition.
||Use long-line chair, two linemen are suspended in midair carrying the new marker ball. Install new marker ball on the line. Remove old marker ball and carry it back to landing space. (Energized line)|
Helicopter work supports safety, knees
The new procedures for using a helicopter for maintenance work have helped meet constrains for environment and outage scheduling, but the biggest benefit is its support for employee safety. “Safety is rule number one,” said Adams. With proper training and strong, safe procedures in place, using a helicopter can be a physical aid on the job. “Using the helicopter for transport decreases fatigue since linemen don’t have to climb every tower; and fatigue increases the likelihood of slips, trips and falls,” said Adams. “It’s less strenuous on [linemen] than climbing. It saves their backs, saves their knees, and it’s an effective way to get the work done in a safe and timely manner. Plus, they like flying on the helicopter.”
In addition to safety, helicopter support leads to:
Reduced impact on environment
The diverse terrain and land use in California means more strict cultural and biological restrictions. Western’s environment folks work hard to proactively coordinate with landowners and Maintenance staff to clear the areas that will be temporarily disturbed by Western’s trucks and work efforts. Using the helicopter lessened the impact on the environment and on Environmental staff because crews do not have to drive out to each structure with big pieces of equipment. “We determine a landing zone that Environment clears for us, and that’s where we work on the ground, just in that zone,” said Adams.
There are still projects that SN crews do from the ground. “It’s what works best for that situation,” said Adams. “The helicopter is another tool in the tool belt. If it’s only one span, we might use the truck. However, if it’s work along the entire line, it makes more sense to use the helicopter.”
Work faster, reduce costs
Incorporating the helicopter has sped up the pace of SN’s projects, allowing them to get several done this summer.
For example, the fiber optic from Cottonwood to Roseville to add goat head peaks (tops to the towers), took one helicopter and 12 people three weeks to install 280 goat peaks. Using a conventional method would have required the line crews to drive to every tower, set up the crane and staging area and climb to the top each time—a job that likely would have taken three months.
In the case of changing out marker balls on the Captain Jack-to-Olinda line, using the helicopter procedure reduced the replacement cost to one fourth of the traditional process. Suspending the linemen as they replace the marker balls mid-air, rather than unclipping the static wire, pulling it to the nearest structure and then letting it back out while hanging new marker balls on the line, meant a two-day $20,000 project rather than a two-week $60,000.
For the space dampener replacements, Adams said they can get about nine spans on a line completed in one day compared to just two or three spans not using the helicopter.
The new processes of using a helicopter for maintenance has seen a few changes in the last three years, but Adams assures that the manual is a living document, meant to provide procedural guidance to continue maintaining the safety of employees and the health of the transmission system in the most cost-effective and efficient way possible.