The physics of an underwater DC line

 In the old company, we had a lot of fun one year looking at the possibility of a big high-voltage line under Lake Erie, from the old Nanticoke coal plant to the US.  That plan will probably be revived when they invade us, and suck out all our resources.

Anyway, lots of fun with geophysics, but it was the line people and not me who did it.  They found a lot of deep trenches and no idea on how that happened.  Luckily, it was a 70's winter and they zoomed by one day when Lake Erie was frozen over.  The ice was forming big pressure ridges, like plate tectonics, but a million times faster.  There were subduction zones, and the ice went down 60 ft.  The whole lake is only that deep.

So, we had to give up on that.  But the interesting thing before the final kabosh, was looking into a DC line.  That's mainly to do with burying the line, and the thermal behaviour.  An AC line interacts with the ground, and blows all the energy.  That's why those lines are so far up towers.  Even then, they blow for long distances.

If you want to push a decent amount of energy down the underwater line, it has to be DC.  That's so wonderful except for the horrible side effects.  Once the line is charged up to speed, it carries a huge momentum with the electrons.  Think of the full zooming 401 without brakes in the cars.

This is all fine, until something happens, like the line gets cut by the Russians.  You have to drain the energy, and it is outrageous.  We found we needed grounding mats the size of Toronto, and even then, all the cows would be killed.  Imagine people!  

So, for these lines in the world, you need to be in the middle of nowhere, and construct huge grounding mats.  Can't put this underwater, or fried swimmers everywhere.  No way you can terminate a DC line in Toronto, and even Darlington is a question.  We could just fill the giant St. Marys cement quarry with copper, and have one end.

In general, the concept of a DC line to the centre of Toronto would make a fine disaster movie.  

ps the other great idea is the tunnel under the 401.  Look at Thailand where they had the nerve to build over a working passenger train line.  Did that work out well?