The following video clip is from the IMAX movie, Striaght Up: Helicopters in Action. It is of a worker who works on high voltage (750k voltsish) wires, while they're live. The commentary is interesting, but I thought it was fascinating how the whole basic system works. He flies in on a helicopter (so he's not touching the ground). First, he needs to bring himself and the helicopter up to the voltage potential of the uninsulated wires, and the biggest issue to that is controlling the arcing. If you watch closely, he has a rod, which is attached to the 'chopper by a cable. He holds it out, and the wires arc across the air to it as the pilot brings them in, close. The technician then makes contact with the rod, which lets him clip on a lead and temporarily connect the helicopter on the wires. He then carefully transfers his gear, climbs over to the wires, clips his rod to the wires, places the rod on the helicopter platform, and unclips the lead. Finally, he holds the rod out away from him as the helicopter departs, followed by a giant arc of electricity.
It's obvious watching it how consciously pre-thought every single move is. One minor lapse in judgement, one quick loss in focus, and you briefly have 750,000 volts going through you - as you're being blasted by the power off your platform and plummeting several stories to the ground. As long as you keep aware of what you're doing, though, it's perfectly safe!