On Mon, 18 Apr 2016 16:37:40 -0000 (UTC), bob
wrote:

Recliner wrote:
Charles Ellson wrote:
On Sun, 17 Apr 2016 18:29:31 -0500, Christopher A. Lee
wrote:

On Sun, 17 Apr 2016 20:56:35 -0000 (UTC), Recliner
wrote:


What's wrong with just using 3rd rail beyond Amersham,

More expensive, obsolete, less efficient and it's heading toward 25kV
territory.

Much *cheaper*, surely? Less efficient, yes, but why should it matter that
it's headed towards 25kV territory?

The high cost of DC 3rd rail comes from the need for more complex and far
more frequent substations. You can get a lot of 25 kV line covered from a
single feed.

Robin

Yes, but you have to weigh the cost of that with the cost of raising
bridges and tunnels, and the disruption while doing this.