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Old February 17th 16, 09:28 AM posted to uk.transport.london
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Default Last class 378 goes 5 car

On Wed, 17 Feb 2016 08:37:58 -0000 (UTC)
Recliner wrote:
Basil Jet wrote:
On 2016\02\17 01:39, wrote:
In article ,
() wrote:

In article

-septembe
r.org,
(Recliner) wrote:

wrote:

Reading the rest of the article, it's a pity they don't make use
of the dual system capability to use overhead AC on the Euston
approaches and simplify the layout there by chucking out the DC
electrification when the changes ahead of HS2 are implemented. I
was amazed to see they're keeping the dual voltage tracks through
those changes.

Yes, it is strange. Perhaps there isn't a suitable voltage change point
on the Euston approach?

I note there are tunnels north of Euston which are only
DC-electrified, just before the dual-electrified section starts.
Maybe they are the problem? Can't the 378s switch while on the move?

That's the bored pair of Primrose Hill tunnels. I suppose they are too tight
for 25KV overhead electrification?


The DC service is presumably DC because it shares track with the
Bakerloo, not because of any clearance issues. Did the adjacent tunnels
have to be enlarged for the catenary?


It doesn't share those tunnels with the Bakerloo, and with dual voltage new
trains, one assumes the non-shared LO tracks into Euston could be 25kV.


Why bother switching over to 25Kv for the last mile if there's a perfectly
good 3rd rail that can be used? It just makes the trip operationally more
complex and the AC kit is an extra point of failure.

--
Spud



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Old February 17th 16, 03:44 PM posted to uk.transport.london
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Default Last class 378 goes 5 car

In article , d () wrote:

On Wed, 17 Feb 2016 08:37:58 -0000 (UTC)
Recliner wrote:
Basil Jet wrote:
On 2016\02\17 01:39,
wrote:
In article ,
() wrote:

In article

-septembe
r.org,
(Recliner) wrote:

wrote:

Reading the rest of the article, it's a pity they don't make use
of the dual system capability to use overhead AC on the Euston
approaches and simplify the layout there by chucking out the DC
electrification when the changes ahead of HS2 are implemented. I
was amazed to see they're keeping the dual voltage tracks through
those changes.

Yes, it is strange. Perhaps there isn't a suitable voltage change
point on the Euston approach?

I note there are tunnels north of Euston which are only
DC-electrified, just before the dual-electrified section starts.
Maybe they are the problem? Can't the 378s switch while on the move?

That's the bored pair of Primrose Hill tunnels. I suppose they are too
tight for 25KV overhead electrification?

The DC service is presumably DC because it shares track with the
Bakerloo, not because of any clearance issues. Did the adjacent tunnels
have to be enlarged for the catenary?


It doesn't share those tunnels with the Bakerloo, and with dual voltage
new trains, one assumes the non-shared LO tracks into Euston could be
25kV.


Why bother switching over to 25Kv for the last mile if there's a perfectly
good 3rd rail that can be used? It just makes the trip operationally more
complex and the AC kit is an extra point of failure.


Because having to have two electrification systems in the Euston throat is a
considerable complication, particularly for the signalling. So it's likely
to lead to more failures.

--
Colin Rosenstiel
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Old February 17th 16, 03:49 PM posted to uk.transport.london
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Default Last class 378 goes 5 car

On Wed, 17 Feb 2016 09:44:42 -0600
wrote:
Because having to have two electrification systems in the Euston throat is a
considerable complication, particularly for the signalling. So it's likely
to lead to more failures.


So is there a high level of signal failures in that area?

--
Spud


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Old February 18th 16, 11:08 AM posted to uk.transport.london
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Posts: 240
Default Last class 378 goes 5 car

In message , Basil Jet
wrote:
The DC service is presumably DC because it shares track with the
Bakerloo, not because of any clearance issues. Did the adjacent tunnels
have to be enlarged for the catenary?


It was built as a DC route because it shared trains with the Bakerloo,
decades before AC electrification came near Euston.

It is quite possible that, since steam wasn't expected to use the lines,
the tunnels were built to a tighter loading gauge. But I don't have data
conveniently available to me.

(You could do a FoIA request on the clearance.)

--
Clive D.W. Feather | Home:
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