No different to birds sitting on live lines, they have to earth it when swapping from the helicopter to the lines I believe, it’s a good watch on YouTube
How do they earth 'it'? The cables are hung on insulators, so the pylon structure cannot carry current unless an insulator fails or a connection is made between the cable and the structure. I somehow reckon there would be a bit of a bang if the structure became live. Does the helicopter drop a cable to ground? But when the painters did the pylons here a couple of years ago, the cables were still live. They had safety lines draped everywhere hanging from the structure, some quite near to the cables.......I assume the safety lines were non-conductive. I have seen plenty of birds sitting on the pylons, but never one sitting on the 400,000 volt cables here. One year, a hot air balloon came bloody close to landing on the cables......the 'pilot' was panicking because it seemed he was either low or had run out of gas for the burner.......he was most certainly chucking ballast off the basket. I reckon the basket was within 50 feet of the highest cables.
Helicopters charge themselves with static so have to ground before landing, if you see a search and rescue man going to pick up a person from a boat, for instance, he will normally be dunked in the sea first to discharge the static charge. Like birds, if you only touch one line then you are theoretically fine. I still don't fancy trying it out
Helicopter and man would be fine standing or connecting to cable as long as they did not touch earth or the other cable. Four sets of lines are 3 phase and earth
Grounding is bad as that is when you get the 400,000 volts providing a current. The difficulty, as I understand it, with HV work is keeping an adequate 'safe' air gap (distance) between the different potentials. Don't try this in the fog!
I thought 3 phase was balanced so you don't need an earth - certainly not of the same gauge cable as the phases.
The insulator length will provide the answer to the safe distance.......if the insulators are 4.0m, the cables are 400,000 volts and the safe distance is 24 feet (although in some circumstances it can vary).
I believe that it is to ground the static generated by the helicopter, albeit your new reference would be 400Kv... And the works are typically carried out live..... not sure i't like to be in the helicopter if it shorts out two phases!
Typically hollow with fibre optics running along it...... some of the first high speed internet connections were done this way... see GLOBAL CROSSING.
I was at a site near Scunthorpe (Ohh the romance of travel) and it was feeding onto 400kV via a bloody great sub, which I got into under flase pretences (that's another story) Anyway when I was there they were doing live line washing, guy had a pressure washer a BIG FEK OFF pressure washer. This thing was designed to pulse jets of water, he was insulated up and nobody was standing too close to him either. Anyway switched on said jetwasher and off he went and blasted the insualtors and such, water was definately getting onto the live lines. He lived!!! The voltage means nothing it's the potential diifference that will kill you. For instance if a line does develop a fault and earths through a pylon, it can kill the coos. This is because as the electrikery leaks to earth from its point source (said pylon) it doesn't ground immediatley due to earth resistance. So this field eminates from the pylon in a rough circle with less votlage as the radius increase. Problem for coos are the poor souls legs are quite far apart and the gap between develops enough potential difference across the ground and electrocutes them So when near a pylon take baby steps wouldn't wany anybody getting roasted
