You could get a charge out of that. High voltage insanity!

What's happening is due to the extraordinarily large voltage, the electricity can jump through the air, as the 'circuit breakers' (giant switches) begin to separate. As this happens the arc (the white lightning) heats the air it jumps through, turning it into a hot plasma, which allows for more electricity to pass through it, so as they gap becomes larger, it still jumps the gap. As the plasma is hotter than the surrounding air, and therefore less dense, it rises, and the path of least resistance begins to be longer and longer, and eventually the arc breaks. Smaller examples of this can occur in your main switchboard, and some circuit breakers in industrial setting have what are called arc chutes, which effectively break up the arc faster.