Why do high voltage transmission line workers need a Faraday cage suit? In this video the high voltage transmission line workers are wearing a Faraday cage suit. Why is this needed?
Without the Faraday cage, the resistance of the human would be very high compared to the transmission line, so practically no current would flow through the worker (i.e. the reason why birds don't get zapped).
With the cage, some current would probably flow through it, but still nothing should go through the worker. The only purpose of the cage that I could think of is that when the man touches (or is near, rather) something (e.g. a tree, or the helicopter) at a different potential than him, the current would go through the cage instead of him. Is this a reason and is it the only one?
A clearer question: why a Faraday suit and not an insulating suit?
 A: My brother-in-law faced this EXACT problem, as he worked on high tension lines.  There is a corona discharge from these lines due to the very high voltages involved.  From experience, the linemen learned that this corona discharge is injurious to internal organs.  To prevent injury, the linemen wear the Faraday cage suit, because such a suit keeps the electric charge on the outside of it (the charge on conductors resides on the outside surface), which prevents any corona discharge effects from entering their body.
High voltage lines come in triplets for a different reason than mentioned below.  Electric generating companies generate 3-phase power, as this is supposed to be more efficient to generate, and I expect that such a power generation practice results in more acceptable mechanical loads on the generators.  Each phase carries AC current, and each phase is 120 degrees out of phase with the other two lines in the triplet.  This means that even though each line in the triplet may carry 100,000 volts rms current, it is easily possible to short one line against the other if two of these lines touch each other or are connected by a conductor.
A: The electric field around high voltage transmission lines (or "high tension" lines) is extremely high, and can be close to the breakdown threshold of air. That's why the highest voltage lines use multiple (often three) parallel conductors, to increase the effective conductor radius and reduce the peak electric field.
Now, introduce a human into that field, and you're going to get conduction. The current won't be high, because the capacitance of an isolated body isn't large, but think of getting a spark off of a door knob, but on a continuous basis, and at a probably higher voltage. At the least it wouldn't be fun, and at the most it would be painful, possibly disabling, and even harmful.
So, comfort and safety dictate that they wear conductive suits.
