High wire act over Indian Arm
Two 230 kilovolt transmission lines stretch high above Indian Arm inlet in the Lower Mainland for over a kilometre. So how do you go about maintaining the transmission line when it’s inaccessible by land or water? Use a helicopter!
An innovative work method has been developed by BC Hydro in collaboration with Blackcomb Helicopters and Manitoba Hydro that uses helicopters and one-person carts to enable power-line technicians to access and work on the lines. This week, the “vibration dampers” needed to be replaced on the lines. The dampers are weights that dissipate wind energy along the span. Without these devices, the conductors can vibrate enough to cause the lattice steel towers to collapse.
The first step is for the power-line technicians to scale the transmission tower and await the chopper as they rest on the tower bridge 85 feet above the ground. Using a long line, the helicopter delivers the cart to the technicians who clip it to the line. Next trip, the helicopter delivers a ladder that the technicians use to climb down safely into the buggy. The cart rides the line like a cable car.
The transmission lines dip like a letter “u” over the water. At the lowest part, the lines are about 160 feet above the water. For the downward slope of the line, the technicians are able to pull themselves along using pulleys and do their work replacing the dampers every 150 feet. But for the upward slope, the grade is too great so the helicopter comes to the rescue. The helicopter drops a long line to the technician in the cart, the technician clips the line to the cart and the helicopter gently pulls the cart back up to the slope to the transmission tower.
The cart and the rider are like birds on a wire. In this case, the work was done on de-energized lines. But even when the lines are energized, the work is done with a safety-first approach. A number of safety and procedural protocols are used including a safety boat carefully watching the work from below and a safety officer watching from the tower. All technicians go through extensive training prior to doing the work.