TOPIC:

I guess you will have seen something like this many times, kawboy.

We have 2 separate electrical grids in Ontario. The old original grid surrounding the "Greater Horse Shoe area" which is basically the area surrounding the west end of Lake Ontario and surrounding southern Ontario and that power grid is a 230Kv grid. The rest of Ontario when developed is a 500KV grid. There is and interconnecting switchyard with transformers. Pickering Nuclear was designed to supply the 230KV grid while the Darlington and Tiverton Nuclear plants supply the 500KV grid.

Each of the running units of each power plant has its own switchyard to connect/disconnect from the grid. Those 3 disconnecting switches are one for each Phase and each disconnect has an air supply of 2,000 psi air that is discharged as the switch is opened to "blow out" the arc and minimize the contact surface damage to the switches.
It can be quite the site when witnessed at night but worse than the sight of it happening is the sound as it happens when the Switchyard Air Supply blows out the arc. I had my back to a switchyard one day when there was a sudden shutdown of one of the running units and the switches blew off. I was maybe 25-30 years of age and at the time, I thought I had a heart attack. There was no announcement over the PA, nothing. It didn't sound anything like what you see on the video. It was more like a 4" cannon going off. Imagine a 2000psi burst going off through a 1-1/2" pipe for one second.

Very interesting.  I imagine it is quite a thrill to witness the switches operating, though probably not good for the eyesight if looking at the arc.  I wonder if the contacts ever actually  ‘weld’ themselves together when closing.
I might have imagined it, but I thought high voltage switches were usually immersed in oil.

Sorry, i can't answer that question. Back in 1986, Ontario Hydro was broken up into 5 different business entities. Ontario Power Generation severed off from Ontario Hydro taking all of the hydraulic, coal fired, gas fired and nuclear generating stations under its wing. Ontario Power Generation Nuclear was spun off of OPG as a separate business entity (which I was part of)  Hydro One became the "transmission division" and maintained the hydro lines, The Independent Electrical System Operator monitored the output power  and operated the switchyards. New Horizons was created and it was responsible for all computer associated Information Technologies. The Electrical Safety Authority took over all of the electrical safety and inspections.

So the switchyards were maintained by Hydro One and we in OPG (N) had nothing to do with the switches, so I can't tell you what was involved in servicing those switches although  Hydro One service trucks were at the plant servicing switchyard gear during unit outages which was 4 outages a year of anywhere between 6 weeks to 18 weeks in length per outage.

I was near the hi-tension lines of Diablo Canyon when an idiot drove a PettyBone crane into the lines.  Scared the crap outta me... The sounds of the crackling, the sounds of all 4 tires bursting, the smell of rubber, ionized air... and the look on the operators face who someone lived... 
 

The smell of burning flesh?