Tuesday, May 10, 2011

Hydro Stringing

Hydro One is in the process of putting in a new tower line (The new transmission line is an approximately 180-kilometre, double-circuit 500 kilovolt (kV) transmission line, extending from the Bruce Power Facility in Kincardine to Hydro One's Milton Switching Station), and now that the towers are up, it was time to start the process of stringing the wires. Just like a simple pole stringing, they workers start with a small rope, which the pull through the pulleys, and as they go, the attach progeressively larger lines, until the final size is pulled into place. Since this line crosses HWY 401 (just east of James Snow Parkway), the Hydro contractor (Valard) brought in an experienced helicopter pilot to fly the rope across the highway. This is a complicated job, with specialized equipment. The firs step involved a pulley like system, called a traveller. Each phase ( basically each wire, and there were 8) had a traveller. On each of these was an arm sticking out (it's the yellow part in the picture), which would guide the rope into place. The helicopter is then equiped with a Johnny Ball, which hangs from the cargo hook at the bottom of the chopper, and hangs down below. The pull rope is attached to the this. Then the helicopter flys slightly past the tower, and using the weight of the Ball, he lowers the line down to the arm of the traveller. Once it hits the arm, it slides down into the pulley, and a one way lock closes. You can see that in the video, as the rope descends from the top left side of the frame.

With the rope locked in place, the helicopter slides sideways to the next tower, and repeats the process. You can see some of the 8 travellers in the picture below. Watching this process, I had to say that the helicopter pilot made it look easy! And when you see what he was dealing with, you quickly realize it was anything but easy! In fact, the previous pilot decided he couldn't do the work, so the contractor brought in a specialist. Now, since all this was happenig over the 401, it required the OPP to run what was known as a rolling blockade. Three cars, were located at the on ramps just east and west of James Snow. As the chopper got closer to the HWY, they then pulled out and slowed traffic down to 5 Km/hr. You can just see them start the process here. Then, both east and westbound traffic were held back, creating a car free highway.

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