Guys go up in a cherry picker and get a first hand experience with high voltage.
An explanation from Reddit:
To expand: these guys are using what is essentially a wearable Faraday cage – it uses a conductive thread. When they get close to the cable, the high voltage in the cable is enough to bridge the air gap between the gloves and the cable. The electricity wants to do this because the suit is connected to the ground, and electricity wants to flow to ground. The air, being a terrible conductor, is superheated through ionisation, giving off the sparks. There is no way for the people to get electrocuted since the electricity will flow through the easiest path, which is through the air, to the glove, down the suit, down a cable into the ground. The electricity has no reason to bother the humans inside the suit because that would just be too much work.