Trivia: Join points between AC and DC

[A Challenge]

Inspired by this question in the Railway General Knowledge Quiz

I am looking for points where AC and DC join, to the point (to set a reference) where it is possible to (even if it not long enough to do without stopping) swap a lets say dual voltage loco from one to the other without needing a diesel loco to pull it along or there being coasting needed.

• Fawkham Jn (Ebbsfleet)
• Ashford International
• Acton Central
• Shepherds Bush (Shepherds Bush to Mitre Bridge Junction)
• Farringdon/City Thameslink
• Drayton Park
• Watford Junction (11 Chains of the Down Fast)
• London Euston to Camden Junction
• Liverpool South Parkway (E end of Hunts Cross Chord) to Hunts Cross

 

[jopsuk]

as well as Fawkham Junction, which is out of use, there's the actual link to the North Kent, with the changeover in platforms 5/6 at Ebbsfleet.
There's an AC-DC link from the Watford DC to the North london Line at Primrose Hill

 

[A Challenge]

I beleive that is actually mentioned now you say that - Willesden Junction Low Level to Willesden Suburban Junction, with the link line being AC only I believe?

 

[87015]

Fairly sure Watford has gone, no connection from Dc to down fast anymore.

"Shepherds Bush" should read North Pole Jn.

Willesden Low Level is DC only, the Ac/DC is on the New Lines there. Over at Primrose Hill the AC/DC section is basically just through the old station for a changeover point (well from Primrose Hill Jn if you want every last chain!)

 

[sjoh]

Reading?

 

[A0wen]

Is there anything on the NLL / ELL between Highbury & Islington and Dalston?

 

[A Challenge]

Reading?

There is nothing there it seems, as it is only into P4-6 DC and P7-15 AC, the joins are neither.

Is there anything on the NLL / ELL between Highbury & Islington and Dalston?

I think there is something there, though not quite what!

 

[pdeaves]

Fairly sure Watford has gone, no connection from Dc to down fast anymore.

According to the sectional appendix, there is still a connection to, and DC electrification on, the down fast line. "Officially" it is still there, whatever it looks like on the ground!

 

[87015]

Is there anything on the NLL / ELL between Highbury & Islington and Dalston?

There is, sort of. It's never been juiced up let alone signed into use.

 

[bramling]

Inspired by this question in the Railway General Knowledge Quiz

I am looking for points where AC and DC join, to the point (to set a reference) where it is possible to (even if it not long enough to do without stopping) swap a lets say dual voltage loco from one to the other without needing a diesel loco to pull it along or there being coasting needed.

• Fawkham Jn (Ebbsfleet)
• Ashford International
• Acton Central
• Shepherds Bush (Shepherds Bush to Mitre Bridge Junction)
• Farringdon/City Thameslink
• Drayton Park
• Watford Junction (11 Chains of the Down Fast)
• London Euston to Camden Junction
• Liverpool South Parkway (E end of Hunts Cross Chord) to Hunts Cross

Can add Dollands Moor yard to this, plus Continental Junction.

 

[pdeaves]

Oh yes, Ashford, Selhurst, Three Bridges and New Cross depots have a bit of OLE in an otherwise DC area. No idea if the actual sidings have the DC rail under the wires or not.

The Asfordby test track has both 3/4 rail and OLE in places.

What about Willesden depot? Does that have 3rd rail and OLE?

 

[rebmcr]

Oh yes, Ashford, Selhurst, Three Bridges and New Cross depots have a bit of OLE in an otherwise DC area.

For testing/prepping dual-voltage stock?

 

[Taunton]

There is, sort of. It's never been juiced up let alone signed into use.

The Dalston to Stratford section was DC only when first electrified in the 1980s, and run with Southern 2-car trains between Richmond and Stratford, later through to North Woolwich, but suffered from considerable "stray currents", which is like a "short-circuit-light" (other definitions by professional electrical engineers would be appreciated), which among other things impacted the Victoria Line signalling where it passes beneath at Highbury. They were difficult to overcome, and given that 25Kv was being installed soon after for North London freights, the changeover was made, and the service converted to dual voltage units, which changed voltage I think 4 times on the journey for a while. Much of the DC east of Acton Central was later removed, the final bit when Stratford to North Woolwich was mostly transferred to the DLR, but for a while it was DC all the way.

 

[edwin_m]

Stray current is where the return current, that should go back to the substation through the rails, leaks out and travels through the earth instead. This is always going to happen to some extent because the rails are never perfectly insulated especially when wet. It can cause problems to signalling systems but the most common effect is corrosion to metal items in the ground due to electrolytic effects. This is only a problem with DC as the reversal of the current in AC cancels out any effect. Possible problems include corrosion of metal gas pipes that run parallel to the railway, with obvious risk of consequences, and damage to the bases of metal OLE poles in dual electrified areas. Stray current is the main reason why DC railways try to isolate themselves from the earth as much as possible, whereas AC railways generally have their rails bonded to earth.

 

[Taunton]

I wonder how street tramways, with DC vehicles and rails actually in the street, and right on top of gas pipes, manage to avoid this.

The most extraordinary account of this I read was in San Francisco, where at Stanford University in the 1960s a biology experiment to measure small electric currents in plants was being wrecked by some stray current source. They felt it was man-made because it only happened in working hours, not overnight or at weekends. It was traced to the BART system, 1000v 3rd rail DC, which had just started test daytime runs of the trains, but was FIVE MILES away from the experiment.

 

[The Planner]

According to the sectional appendix, there is still a connection to, and DC electrification on, the down fast line. "Officially" it is still there, whatever it looks like on the ground!

As 87015 says, I'm also pretty sure the DC got taken out as part of Watford resignalling.

 

[Boodiggy]

As 87015 says, I'm also pretty sure the DC got taken out as part of Watford resignalling.

The crossover is still there, although points clipped in normal and no moves have been made since the completion of the Watford works...
Connection in to the tip siding was removed though.

 

[edwin_m]

I wonder how street tramways, with DC vehicles and rails actually in the street, and right on top of gas pipes, manage to avoid this.

I suspect it was just treated as "one of those things", especially as the municipality generally owned both the tramway and the utilities. That was certainly what they told me when I asked the question of one of the German tramway operators fifteen or so years back. Of course for the modern light rail revival in the UK the pipes are now owned by privatised utilities so there is every chance of the lawyers getting involved if something goes wrong.

The most extraordinary account of this I read was in San Francisco, where at Stanford University in the 1960s a biology experiment to measure small electric currents in plants was being wrecked by some stray current source. They felt it was man-made because it only happened in working hours, not overnight or at weekends. It was traced to the BART system, 1000v 3rd rail DC, which had just started test daytime runs of the trains, but was FIVE MILES away from the experiment.

Oddly enough someone asked me on Friday whether I could do some estimates of whether a tram could coast through a dead section on a future UK route without losing too much speed. The reason is EMC issues with a nearby facility.

 

[snowball]

Oddly enough someone asked me on Friday whether I could do some estimates of whether a tram could coast through a dead section on a future UK route without losing too much speed. The reason is EMC issues with a nearby facility.

You may not be able to say who and where you were asked about, but the Metrolink Trafford Park line, now under construction, underwent a route amendment while still at the planning stage because of possible EMC effects on a nearby company.

 

[SpacePhoenix]

Looking at a few pictures of Dollands Moor might have at least one track with both 3rd rail and OLE. I've no idea if the 3rd rail is used (or has ever been used)

 

[pdeaves]

For testing/prepping dual-voltage stock?

Yes, exactly.

 

[GW43125]

There is nothing there it seems, as it is only into P4-6 DC and P7-15 AC, the joins are neither.

Didn't they put some DC on the diveunder and into some of the RL platforms or have I made that up?

 

[swt_passenger]

Didn't they put some DC on the diveunder and into some of the RL platforms or have I made that up?

The DfT announced at one stage that steel sleepers were being installed on the relief side to make it easier to subsequently continue third rail into platforms 13-15. After much ridicule it turned out they had installed the usual concrete sleepers used on the DC network, ie pre-fitted with threaded inserts to install insulators.

Subsequently there has been no news of any future dual electrification. I doubt it will ever be thought about until the North Downs ever gets electrified.

 

[Taunton]

One that disappeared was Manchester Piccadilly, when the Woodhead 1500v DC overhead was in use up to the 1980s, where the lowest numbered platforms were DC and the remainder 25Kv AC. On the approach the different systems side-by-side were hung from the same gantries. There were a couple of crossovers across the layout, unelectrified, for use of diesels.

 

[jamesbwxm]

Oddly enough someone asked me on Friday whether I could do some estimates of whether a tram could coast through a dead section on a future UK route without losing too much speed. The reason is EMC issues with a nearby facility.

I'm not at liberty to say where except that it's not in the UK but I'm currently dealing with an expensive scientific instrument involving highly precise magnetic fields being shifted every time a tram goes over the underground lab facility. It was certainly a headscratcher to begin with.

 

[edwin_m]

The DfT announced at one stage that steel sleepers were being installed on the relief side to make it easier to subsequently continue third rail into platforms 13-15. After much ridicule it turned out they had installed the usual concrete sleepers used on the DC network, ie pre-fitted with threaded inserts to install insulators.

Subsequently there has been no news of any future dual electrification. I doubt it will ever be thought about until the North Downs ever gets electrified.

The cause of the ridicule being, I presume, the fact that steel sleepers are forbidden on third rail lines.