What they were doing: no fucking idea, but that thing there is the equivalent of a HUGE light switch. (They were rerouting power or something).
Why that happens: when it first seperated, the current differences between the two contacts and the high voltage were enough to overcome the insulation properties of the air, so it arced. It continued arcing due to those above mentioned causes and becuase when electricity arcs through the air, it oxidizes the air and creates ozone.
The ozone cunducts electricity better than air so the electricity conintued to arc through the ozone. But, ozone is lighter than air (that's why it's all in the atmosphere) and so it began to float upwards. The electricity followed becuase even though it was a further path to travel, it still had less resistance than the air.
This continued until the ozone dissapated enough and/or the voltage couldn't handle the long distance.
Or at least I think. It's been a few years seen physics classes.
500kV Line Opened Under Load
Linear Mode
