Thameslink - power changeover question

[Alex TM]

Hi folks,

 

This week I had the opportunity to make several trips on the Thameslink network, with all journeys going without a hitch.  One questions did arise:

 

     where do the units switch from overhead lines to third rail pick-up?

 

As a follow-up, I also wondered how the changeover was done as there seemed to be no loss of power nor was there any unduly long wait at any station to drop the pantograph or check the electrical supply?

Any information will be gratefully received.

 

Thanks and regards,

 

Alex.

[chris p bacon]

IIRC it's done at Farringdon when the units are stationary. The shoe is on the 3rd rail as the pan is dropped.

[DY444]

1 hour ago, chris p bacon said:

IIRC it's done at Farringdon when the units are stationary. The shoe is on the 3rd rail as the pan is dropped.

 

It's done at Farringdon southbound but at City Thameslink northbound. 

[bécasse]

It used to be done at Farringdon in both directions but as DY444 says it is now done at City Thameslink NB.

 

Doing it while stationary at a station is a doddle, prior to the inauguration of HS1 Eurostar's 373s used to do it in the vicinity of Dollands Moor at full line speed.

[The Stationmaster]

1 hour ago, bécasse said:

It used to be done at Farringdon in both directions but as DY444 says it is now done at City Thameslink NB.

 

Doing it while stationary at a station is a doddle, prior to the inauguration of HS1 Eurostar's 373s used to do it in the vicinity of Dollands Moor at full line speed.

Occasionally resulting in some 'interesting' collisions between the pantograph and certain items of infrastructure.  I think there might still be evidence of such a collison on the footbridge at Sandling which was definitely the result of a rather different sort of attempted changeover.  It used to cause considerable hilarity at North Pole Eurostar depot where the control room gave an excellent view of EMUs stopping to changeover from overhead to 3rd rail on the West London Line where there was plenty of room to coast down North Pole bank and the overhead extended most of the way to the Westway overbridge. (which was also hit by  Eurostar Class 373 pan on one occasion but that had nothing to do with a changeover - in that case the ECS had left the depot on the wrong system)

 

Changeover on the run at line speed  is a standard feature of continental operation - including going onto/off the LGVs in France - and of course in some instances at national borders where the two rail systems are using different voltages etc

[DY444]

17 hours ago, bécasse said:

Doing it while stationary at a station is a doddle, prior to the inauguration of HS1 Eurostar's 373s used to do it in the vicinity of Dollands Moor at full line speed.

 

.. and after that for a while on the spur between Fawkham Jn and the first stage of HS1.  Another tricky location iirc especially for London bound trains with a steep downhill gradient on HS1 before the speed restriction onto the spur, a relatively short changeover zone, and a good chance of a red at the signal protecting Fawkham Jn.   I recall one Eurostar driver telling me the order of business was get it slowed down, get the pan down sharpish and worry about the rest afterwards.

[St. Simon]

17 hours ago, bécasse said:

It used to be done at Farringdon in both directions but as DY444 says it is now done at City Thameslink NB.

 

Doing it while stationary at a station is a doddle, prior to the inauguration of HS1 Eurostar's 373s used to do it in the vicinity of Dollands Moor at full line speed.

 

I assume now the PCO is handled by the Automatically via the Level 2 ETCS Packet 39 or 44.

 

Simon

[phil-b259]

3 minutes ago, St. Simon said:

 

I assume now the PCO is handled by the Automatically via the Level 2 ETCS Packet 39 or 44.

 

Simon

 

Yes - but due to issues with driver training the number of trains actually using ECTS/ATO (as opposed to drivers using the lineside signalling that is still present throughout) can be as low as 30% and this is particularly true when service disruption occurs.

 

Even on a good day the number of ECTS /ATO run trains only gets to the 70-80% mark

[phil-b259]

18 hours ago, bécasse said:

It used to be done at Farringdon in both directions but as DY444 says it is now done at City Thameslink NB.

 

Doing it while stationary at a station is a doddle, prior to the inauguration of HS1 Eurostar's 373s used to do it in the vicinity of Dollands Moor at full line speed.

 

To be fair, on a urban train service it makes perfect sense to do the changeover while calling at a station as opposed to doing it at speed. It also gives the opportunity for the train to be easily recovered if the changeover is defective  or simply gives time for the driver to try and fix the issue without the train sitting in the middle of nowhere with passengers far more likley to get restless on urban trains than on longer InterCity trips.

 

On the GN trains change over while calling at Drayton Park while on the NLL the changeover is done at Acton Central.

 

In an ideal world the WLL changeover would be done at Shepherds Bush but the height of the Westway bridge precludes this.

[009 micro modeller]

18 hours ago, bécasse said:

It used to be done at Farringdon in both directions but as DY444 says it is now done at City Thameslink NB.

I thought this might be the case. I had wondered (while commuting on it) why there seemed to be an overlap but had wondered if it might just be a dead section in case the pantograph fails to drop, like on the line to Moorgate. There are visible signs on the southbound platform at Farringdon advising that it is the changeover point.

 

Is there a specific reason why the northbound changeover is at City Thameslink?

Edited September 26, 2022 by 009 micro modeller

[The Stationmaster]

58 minutes ago, DY444 said:

 

.. and after that for a while on the spur between Fawkham Jn and the first stage of HS1.  Another tricky location iirc especially for London bound trains with a steep downhill gradient on HS1 before the speed restriction onto the spur, a relatively short changeover zone, and a good chance of a red at the signal protecting Fawkham Jn.   I recall one Eurostar driver telling me the order of business was get it slowed down, get the pan down sharpish and worry about the rest afterwards.

Yes - quite a few potential problems emerged at the various CTRL boundaries with other signalling systems when we doing the SPAD Risk assessments for them.  One assessment however descended into total farce and that was at the transition from TVM to the originally intended lineside signalling coming out of the tunnel/covered way over the ECML.  on the set of drawings that were considered for the SPAD risk assessment there was a neutral section on the rising gradient out of the tunnel at very close to the spot where the Driver would get first sight of the first lineside signal.   So the electrification engineers were called in to ascertain if the neutral section could be moved and quite where the project had dug them up from was a mystery because they immediately started talking about the position of the APC magnets in relation to the site of the first AWS magnet.  That got them lots of blank, or down right astonished, looks as everybody was amazed to hear that APC magnets would be involved so some serious questions were asked.  It then turned out that these two 'electrification engineers' hadn't got the first idea about the electrification on CTRL and, it gradually emerged, there was no reason for this phantom neutral section anyway, problem resolved.

 

All the changeovers, but particularly the short ones such as those at Ashford and Fawkham,  involve(d) quite a high Driver workload with varying potential levels of risk of something not be done in the correct order or not being done at all.  Interestingly that doesn't seem to have been the situation with the changeover from CTRL to 3rd rall (and change of signalling system) at Continental Jcn.  The risk assessment for there identified the potential for two failures in 100 years of running but only one of the two that occurred reflected the consequences of a slow/late changeover and the pan of an inbound train hit the signal gantry at the entrance to Saltwood Tunnel.

 

The other was definitely way off anybody's thought processes as it occurred with an inbound train at the other (i.e. inland) end of Saltwood Tunnel where, having correctly changed over from overhead to 3rd rail approaching Continental Jcn,  an SNCF Driver then raised the pan after leaving the tunnel and it hit the footbridge at Sandling.

[John M Upton]

Mind you, a few Thameslink's, particularly in the Class 319 era did manage to set off southbound from Farringdon with the pantograph still up, until it reached the first low overhead structure....

Edited September 26, 2022 by John M Upton

[Tom Burnham]

16 hours ago, 009 micro modeller said:

I thought this might be the case. I had wondered (while commuting on it) why there seemed to be an overlap but had wondered if it might just be a dead section in case the pantograph fails to drop, like on the line to Moorgate. There are visible signs on the southbound platform at Farringdon advising that it is the changeover point.

 

Is there a specific reason why the northbound changeover is at City Thameslink?

Am I right in thinking that there are or were some stabling sidings in the darkness just north of City Thameslink?  Never used much I believe but perhaps they would have allowed a third rail only unit to be got out of the way if it had been signalled on to Thameslink rather than the terminal platforms at Blackfriars in the early days.

[Edwin_m]

31 minutes ago, Tom Burnham said:

Am I right in thinking that there are or were some stabling sidings in the darkness just north of City Thameslink?  Never used much I believe but perhaps they would have allowed a third rail only unit to be got out of the way if it had been signalled on to Thameslink rather than the terminal platforms at Blackfriars in the early days.

Smithfield Sidings, but they are only long enough for an 8-car unit.  

 

I seem to recall the reason for the overlap of systems between City Thameslink and Farringdon was so the train would attempt to change systems at the first of those stations, but if that failed it could continue to the other one, and reverse out via the crossovers in between.  

[009 micro modeller]

3 minutes ago, Edwin_m said:

I seem to recall the reason for the overlap of systems between City Thameslink and Farringdon was so the train would attempt to change systems at the first of those stations, but if that failed it could continue to the other one, and reverse out via the crossovers in between.  

But is there any reason for now routinely doing the northbound changeover at City Thameslink?

[Tom Burnham]

Thanks. 8 cars would have been OK in the early days of Thameslink as the Holborn/Blackfriars section of the SE Division had 8-car trains even after the CX/Cannon Street lines went to 10.

[Wickham Green too]

20 minutes ago, 009 micro modeller said:

But is there any reason for now routinely doing the northbound changeover at City Thameslink?

er .... 'cos its the 'first of those stations' p'raps ??!?

[009 micro modeller]

21 minutes ago, Tom Burnham said:

Thanks. 8 cars would have been OK in the early days of Thameslink as the Holborn/Blackfriars section of the SE Division had 8-car trains even after the CX/Cannon Street lines went to 10.

Some trains through the core are still 8 coaches although a lot are 12 now.

[phil-b259]

38 minutes ago, 009 micro modeller said:

But is there any reason for now routinely doing the northbound changeover at City Thameslink?

 

If its an 8 car unit it can go into Smithfield sidings.

 

If its a 12 car unit it can go forward to Faringdon and swap lines before returning still under 3rd rail power. Remember with Thameslinks high frequency if a train has a problem then the driver simply swapping ends at City or Farringdon won't work as there will usually be a queue of trains behind

[phil-b259]

15 minutes ago, 009 micro modeller said:

Some trains through the core are still 8 coaches although a lot are 12 now.

 

All trains routed via Elephant & Castle (thats those on the Wimbledon loop and Shortlands) can only be 8 cars due to short platform lengths.

 

If you do see a 12 cart on this route it will be a (slow) non-stop diversion away from London Bridge via Streatham Common and Herne Hill

[009 micro modeller]

19 minutes ago, phil-b259 said:

 

All trains routed via Elephant & Castle (thats those on the Wimbledon loop and Shortlands) can only be 8 cars due to short platform lengths.

 

If you do see a 12 cart on this route it will be a (slow) non-stop diversion away from London Bridge via Streatham Common and Herne Hill

Likewise, the peak hours only Welwyn Garden to Sevenoaks services are 8 cars, because not all the Great Northern platforms they call at are long enough for 12.

[keefer]

The use of 12-car trains for Thameslink etc. was what did for the Widened Lines from Farringdon-Moorgate.

There wasn't room to extend the Southbound platform enough at the North end, so they had to extend the south end - right over the crossovers to Moorgate.

Farringdon is interesting as in modern times there were:

1) line to Moorgate open, line via Snow Hill abandoned.

2) both lines open

3) line to Moorgate abandoned, line via Snow Hill open.

http://www.abandonedstations.org.uk/WidenedLines.html

Edited September 27, 2022 by keefer

[009 micro modeller]

48 minutes ago, keefer said:

The use of 12-car trains for Thameslink etc. was what did for the Widened Lines from Farringdon-Moorgate.

There wasn't room to extend the Southbound platform enough at the North end, so they had to extend the south end - right over the crossovers to Moorgate.

Farringdon is interesting as in modern times there were:

1) line to Moorgate open, line via Snow Hill abandoned.

2) both lines open

3) line to Moorgate abandoned, line via Snow Hill open.

http://www.abandonedstations.org.uk/WidenedLines.html

Had the Thameslink line to Moorgate remained open a bit longer, it would have become (at least technically) possible once again to operate a train from the Great Northern lines to Moorgate via the Widened Lines (as opposed to via the deep level Northern City Line, as is done nowadays).

[Michael Hodgson]

2 hours ago, 009 micro modeller said:

Had the Thameslink line to Moorgate remained open a bit longer, it would have become (at least technically) possible once again to operate a train from the Great Northern lines to Moorgate via the Widened Lines (as opposed to via the deep level Northern City Line, as is done nowadays).

Yes, but that route to Moorgate is also important, as it not only serves stations on the ex-tube line, but also provides interchange with the North London lines.

[009 micro modeller]

3 minutes ago, Michael Hodgson said:

Yes, but that route to Moorgate is also important, as it not only serves stations on the ex-tube line, but also provides interchange with the North London lines.

I know, I was just thinking about it as a point of interest. The Northern City Line also has its own very interesting history.