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Colin Rosenstiel · February 15th 08, 11:41 PM posted to uk.transport.london

In article
,
(Andy) wrote:

On Feb 15, 8:09*pm, (Colin Rosenstiel) wrote:
In article

,

(John B) wrote:
On 15 Feb, 13:59, (Colin Rosenstiel) wrote:
How do they cope with 6-car 313 trains on the GN then?

The power supply on the GN can cope with them. The power supply

on the DC lines can't (according to a recent thread).

But the GN has DC lines from Drayton Park to Moorgate. The trains
are limited to 30 MPH (series only) but I thought that was
because of the tunnels, not the power supply.

It's not that DC is inherently incapable (see: 12-car Desiros on
SWT, which draw more than 2x the power of a 6-car 313), it's that
the specific actual DC power system, substations, cabling, etc that

was installed on the North London Railway in 1916, even with
whatever upgrading it's received since, is not capable. The system
installed in the GN in the mid-1970s was much more powerful...

[see also: electric trains north of Cambridge or between Leeds and
Skipton. 25kV AC is perfectly capable of handling TGVs and massive
freight trains, but the systems installed in the 1980s can only
handle a couple of EMU...]

But the power supply North of Queen's Park could handle 1680HP
1938TS. So why not a mere 6 cars of class 313?

I think that there might be some mixing of problems here. I think that
the North London line is the route limited to 3 car 313s, this was
electrified before the DC lines even existed (in 1916). The closure of
Broad Street and extension to North Woolwich was done on the cheap and
I think this was the part with supply problems. With the closure
beyond Stratford and the electrification of the new platforms there
with AC, I think that any restriction will disappear, as most of the
route will then be AC electrified. The DC Lines from Euston don't have
such the restriction, as they were a busier railway, designed to cope
with the Bakerloo stock all the way to Watford. However, there may
still be a problem of peak current drawn and things may have changed
with any re-equiping of the power supply.

The makes more sense. There is no reason why the power supply shortage
shouldn't apply to AC as well (see North of Milton on the line to King's
Lynn) but it's less likely to be a problem in an urban area where
National Grid feeds aren't so hard to find.

--
Colin Rosenstiel