PSE&G line crews use a specialized helicopter platform to work on energized power lines.
Linemen often scale transmission towers or climb inside of an aerial bucket to repair or replace power lines in the Northeast. Because of treacherous terrain or extreme weather conditions, however, it's sometimes impossible for field crews to drive their vehicles to their work destinations.
Five years ago, Public Service Electric & Gas (PSE&G; Newark, New Jersey) began conceptualizing a specialized platform for a helicopter. The one platform that was available at that time was under patent protection and could only be used by one utility, so PSE&G began developing a safe work platform that could be used by the entire utility industry and was available to all linemen.
After securing an experimental certificate, PSE&G met with the director of the Occupational Safety and Health Administration (OSHA) to brainstorm a solution. In addition, utility employees met with Roger Coffman, a professor of aeronautic engineering at George Washington University. The professor challenged his students to devise the ultimate helicopter platform, and at the completion of the project, PSE&G was able to select from five different designs.
Devising the Design
The product development process took several years. After performing the physical aerodynamic testing, PSE&G took the platform to the high-voltage lab at the Electric Power Research Institute (EPRI; Palo Alto, California) for electrical testing. If the entire platform was energized at 500,000 V, PSE&G didn't want the voltage to affect the helicopter operation.
After ensuring the platform's safety, PSE&G came up with three different sized platforms, which can be mounted to the belly of the utility's helicopter. Each platform has a specific intended function for inspections, live line work or ground shield work.
Linemen can use the inspection platform outside of the helicopter with line inspection cameras and patrol equipment. They also can work on energized conductors on the conductor platform or move the wire away from the structure on the ground shield platform.
To protect both the helicopter pilot and the linemen, PSE&G designed the platforms so there is a weight and balance system. As the linemen and their equipment load up one side of the platform, a computer system counterbalances the weight with a 4-to-1 ratio. This allows the helicopter pilot to reduce the amount of gross load on the platform and enables the linemen to perform more work with less fuel usage.
In some cases, the linemen will ride inside the helicopter with the pilot. If the field crew only has to travel a short distance to the work location, however, the pilot will load the linemen and their tools on to the work platform at the airport. Using an off-landing permit, the pilot will then fly the linemen to the designated pole or structure, and the linemen will stay on the platform until they land back on the ground at the airport.
Protection from Electrocution
In addition to wearing harnesses, the linemen also don metal mesh suits called Faraday suits to protect them from electrocution. These metal jumpsuits work on the Faraday Principle by allowing electricity to flow around the suit instead of through it and the person inside.
The Faraday cage keeps the lineman at the same potential as the line conductor. As the helicopter flies in close proximity to the energized line, the lineman uses a bonding wand to pick up the static charge of the current. The lineman then transfers it from the outer structure of the helicopter so that he or she, the pilot and the aircraft are all energized at the same potential, which ranges between 138,000 V to 500,000 V.
The principle works similarly to a bird sitting on an electric wire. As long as the linemen aren't connected to the ground, the electricity can't complete the circuit. Oftentimes, it's safer for the lineman to be in the helicopter than an aerial lift because there is no path to the ground. By bonding everything to the air frame and taking that initial arcing surge of about 400 A, nothing will burn up in the helicopter, and it will be safe to use.
Since even a small amount of current flow can be lethal to a lineman, PSE&G developed a bus bar. This bar is folded into the helicopter, which features an aluminum floor. Because everything is energized at the same potential, there is no risk of electrocution while the linemen are working on the energized lines from the helicopter platform.
Before allowing the linemen to perform energized work in the helicopter, PSE&G first requires them to train on land. Apprentices spend about three years doing non-energized work, and then they move to live work out in the field. At the completion of their seven-and-a-half-year training program, they can then specialize in aerial live line work.
Improving the Quality of Inspections
After training the linemen to perform the aerial live line work, the utility then allows them to use the helicopter to repair and maintain remote lines. Oftentimes, PSE&G's lines cut through meadows or marshes. While it can be challenging for field crews to access these lines with traditional equipment like aerial bucket trucks, the usage of the company's helicopter helps them to easily reach their intended destination.
In addition to using the helicopter to help to repair and maintain the transmission lines, the linemen often use the helicopters for routine line inspections, tree surveys and right-of-way surveys.
To properly document the condition of the line, structures and vegetation in PSE&G's service territory, the company worked with Tyler Camera Mount, a California firm that specializes in mounting equipment for helicopters. Tyler Camera Mount has worked with Hollywood film studios to attach cameras to helicopters for movie shoots.
By patrolling the service territory from the air rather than by land, PSE&G is able to increase its efficiency ten-fold. The linemen also are able to conduct higher-quality inspections, because they are able to see more from the helicopter platform than they would if they were inside of the aircraft.
However, as with any field practice, safety is always a top priority for the linemen whether they're doing a line inspection or repairing a damaged line. Before the linemen ever step onto the platform, they're already wearing a full-body harness. That way, they are protected from falling from the platform while the helicopter is in flight. PSE&G also modified the platform to include a foot rest so their feet no longer dangle below the skids.
Working Hot to Improve Reliability
PSE&G strives to have its transmission grid at 100% at all times. Whenever the utility has to take a line out for maintenance and alter the power flow of the grid, the company tries to continue to work with the lines energized so it creates less havoc on the system.
Prior to investing in the helicopter, all of the utility's hot work was land-based through insulating ladders and hot sticks. Now that the utility has a helicopter, PSE&G has enough equipment in its tool bag to handle any energized job that is out there. Each piece of equipment — ladders, hot sticks and even helicopters — have their limitations, but by having access to all three of them, the linemen can maintain the system energized at all times.
Many companies are offering helicopter services to electric utility companies, but after conducting a financial analysis, PSE&G determined that it was advantageous to own its own helicopter. That way, the linemen can have access to the helicopter at a moment's notice, and the field crews are able to increase their productivity.
By helping to invent the platform and investing in its own helicopter, PSE&G is able to boost the productivity of its field workforce during line maintenance and inspection patrol missions. For PSE&G, the helicopter is another tool that the linemen can use to get their job done safely and securely.
Tom Verdecchio (firstname.lastname@example.org) is a senior live line coordinator for PSE&G and has been with the company for 39 years.
Joseph Fitzgerald is the manager of transmission construction and maintenance and has been with the company for 42 years.