Electrification over flat crossings

[Aictos]

One for those more versed in the workings of both 3rd rail and OHL but if both routes are electrified on both systems, how are they setup?

I would have thought with 3rd rail you have gaps over the flat crossing but how would it work with OHL?

I know Newark flat crossing has OHL but that is only on one route which is the ECML not the Lincoln to Nottingham route so how would they have OHL for this location if both routes were electrified at OHL?

 

[Bald Rick]

To my knowledge there aren’t any ‘flat’ crossings like Newark on the NR network electrified at AC.

However there are plenty of diamond crossing with big angles. These work with very carefully positioned (registered) contact wire, or in older installations in low speed layouts one wire is simply immediately above the other and the profile of the pantograph head does the job.

 

[Aictos]

To my knowledge there aren’t any ‘flat’ crossings like Newark on the NR network electrified at AC.

However there are plenty of diamond crossing with big angles. These work with very carefully positioned (registered) contact wire, or in older installations in low speed layouts one wire is simply immediately above the other and the profile of the pantograph head does the job.

But would it be possible to electrify a flat crossing such as Newark at some point in the future if the business case stacked up?

 

[Ken H]

but at a junction you also have to keep the lined electrically separated.
I tried to find a pic, but I mean component in the contact wire, with a v. sort if looks like <-
There is a ceramic insulator separating the v from the 'hyphen'
What is this called and anyone got a pic?

In the example at Newark, I assume the Newark castle line would have a neutral section each side of the ECML. The circuit breaker on the train, which would be open because of the APC magnets, would mean it would not be drawing current as it went over the crossing. The brief time the pan was connected to the ECML, the circuit breaker would be open so no current could be drawn. ECML trains would draw current over the crossing.
I think the rails would need to be electrically isolated over the crossing too.

 

[Aictos]

but at a junction you also have to keep the lined electrically separated.
I tried to find a pic, but I mean component in the contact wire, with a v. sort if looks like <-
There is a ceramic insulator separating the v from the 'hyphen'
What is this called and anyone got a pic?

In the example at Newark, I assume the Newark castle line would have a neutral section each side of the ECML. The circuit breaker on the train, which would be open because of the APC magnets, would mean it would not be drawing current as it went over the crossing. The brief time the pan was connected to the ECML, the circuit breaker would be open so no current could be drawn. ECML trains would draw current over the crossing.
I think the rails would need to be electrically isolated over the crossing too.

This is why I’ve spent the entire weekend mulling over if it’s possible or not.

 

[Bald Rick]

but at a junction you also have to keep the lined electrically separated.

They don’t have to be, and often aren’t.

A neutral section (separating 2 electrical feeds) isn’t the same as a section insulator (separating individual stretches of track from the same feed)

 

[59CosG95]

but at a junction you also have to keep the lined electrically separated.
I tried to find a pic, but I mean component in the contact wire, with a v. sort if looks like <-
There is a ceramic insulator separating the v from the 'hyphen'
What is this called and anyone got a pic?

In the example at Newark, I assume the Newark castle line would have a neutral section each side of the ECML. The circuit breaker on the train, which would be open because of the APC magnets, would mean it would not be drawing current as it went over the crossing. The brief time the pan was connected to the ECML, the circuit breaker would be open so no current could be drawn. ECML trains would draw current over the crossing.
I think the rails would need to be electrically isolated over the crossing too.

Something like this, perchance?

This is a Section Insulator, usually used at crossovers to keep wire runs electrically separate for sectioning purposes.
A more modern version:


It might be feasible to have 4 SIs (2 per track) either side of the ECML, but you'd have to squeeze another two in on each Newark Castle-Lincoln track between the two ECML tracks, and probably have to add new structures in to support the SIs (as they're really quite heavy!). All this might make such a wiring scheme for that line completely untenable with the current track configuration, and I'll bet that NR would want to grade-separate the two lines before they electrify it (if, of course, they ever do).

 

[Bald Rick]

But would it be possible to electrify a flat crossing such as Newark at some point in the future if the business case stacked up?

Yes, definitely. It would quite likely to be electrified with conductor bar, other wise maintaining tension could be quite complex.

There used to be a flat crossing in Melbourne, which had both lines electrified. One was the local commuter lines and the other was the tram; the former 1500v D.C. the latter 750! All done with wires and lots of in line insulators.

It’s not there now as the tram now goes over a new bridge (with the road it was on).

 

[civ-eng-jim]

To my knowledge there aren’t any ‘flat’ crossings like Newark on the NR network electrified at AC.

However there are plenty of diamond crossing with big angles. These work with very carefully positioned (registered) contact wire, or in older installations in low speed layouts one wire is simply immediately above the other and the profile of the pantograph head does the job.

If I understand the arrangement correctly, a cross contact bar works for crossings where there is an angle but going to the extreme of a right angle interface, the pantograph on the higher wire would clobber the lower wire.

Newark has an angle of 44.6 degrees, but I'm not sure at what angle the cross contact bar would be for the pantograph to start hitting the lower wire rather than smoothly transitioning as you described .

 

[Ken H]

Something like this, perchance?
View attachment 68328
This is a Section Insulator, usually used at crossovers to keep wire runs electrically separate for sectioning purposes.
A more modern version:
View attachment 68329

It might be feasible to have 4 SIs (2 per track) either side of the ECML, but you'd have to squeeze another two in on each Newark Castle-Lincoln track between the two ECML tracks, and probably have to add new structures in to support the SIs (as they're really quite heavy!). All this might make such a wiring scheme for that line completely untenable with the current track configuration, and I'll bet that NR would want to grade-separate the two lines before they electrify it (if, of course, they ever do).

Thats just the thing I meant. Thanks.

But it has a socking great insulator in it, so it must be keeping bits of the overhead electrically isolated.

 

[59CosG95]

Yes, definitely. It would quite likely to be electrified with conductor bar, other wise maintaining tension could be quite complex.

There used to be a flat crossing in Melbourne, which had both lines electrified. One was the local commuter lines and the other was the tram; the former 1500v D.C. the latter 750! All done with wires and lots of in line insulators.

It’s not there now as the tram now goes over a new bridge (with the road it was on).

I believe that was at Kooyong (although Garry Keenor's Overhead Electrification for Railways book states that the tram voltage was 600V DC). It may well have been possible to insulate a single tramway contact wire between two C&C wire runs, but doing it with 2 C&C wire runs crossing 2 C&C wire runs (of which the latter pair runs at 125mph), combined with our hugely restrictive loading gauge, makes it a very painful position indeed.

 

[59CosG95]

Thats just the thing I meant. Thanks.

But it has a socking great insulator in it, so it must be keeping bits of the overhead electrically isolated.

Happy to help! Some of them have a more in-line glass-fibre Rod insulator instead, which is a bit more discreet, but that tends to be reflected in the price.

 

[Bald Rick]

A

I believe that was at Kooyong (although Garry Keenor's Overhead Electrification for Railways book states that the tram voltage was 600V DC). It may well have been possible to insulate a single tramway contact wire between two C&C wire runs, but doing it with 2 C&C wire runs crossing 2 C&C wire runs (of which the latter pair runs at 125mph), combined with our hugely restrictive loading gauge, makes it a very painful position indeed.

The Melbourne crossing was 2 tracks crossing two tracks, I have a picture somewhere. It may well be 600V, my mistake.

Agreed it would be difficult for high speed, hence I think conductor bar would be the answer. (And the ECML is 100mph across the flat crossing, not that it makes much difference!)

Edit: the Melbourne one I was thinking of is Burke Road, Gardiner. However there is another one still in use at Glen Huntly. You can see it on google street view.

 

[edwin_m]

Any rail enthusiast who happens to be in Rome should at least take a look at Porta Maggiore. There is a "tram roundabout" with a narrow gauge line across the middle which appears to be electrified on a different voltage. As far as I could tell the overhead line at the crossing was isolated and switched to the correct voltage depending on what was approaching. Plus a Roman aqueduct passing over the whole lot.

 

[ComUtoR]

To my knowledge there aren’t any ‘flat’ crossings like Newark on the NR network electrified at AC.

However there are plenty of diamond crossing with big angles.

What is a 'flat crossing' compared to a 'diamond crossing' ? (cheers in advance as always)

I'm under the wires all the time going across junctions and crossovers etc. Going into and out of Cricklewood means your constantly crossing over sets of points.

 

[Ken H]

On a double track railway, can you connect the 2 tracks cantenery electrically, or must they be insulated from each other?

if they must be insulated from each other, then how would a double junction be organised in the knitting?

 

[pdeaves]

What is a 'flat crossing' compared to a 'diamond crossing' ? (cheers in advance as always)

Flat crossing is akin to a level crossing, but with two railways rather than one railway and one road. Diamond crossing is likely smaller/nicer angles as it is used as part of normal 'points and crossings' arrangements to get the train from one side of the formation to the other and that type of thing.
Or something a bit like that!

 

[Ploughman]

Would some sort of dish or flat cone made of an insulating material and attached to each wire run provide a solution?
With the Pantograph running off the wire across the dish and back on to the wire run.
The dish allowing the pantograph to run on and off in any direction and any angle.

 

[Edders23]

surely a heavier duty version of the above in a cross shape would work but probably with the whole crossing area neutral. It must be possible if complicated pointwork can be wired a flat crossing should be wireable

 

[Dave_Cardboard]

I bow to the wisdom of those who know what they are talking about, but for such as relatively short running distance (whatever direction) would it "not be worth the hassle" of arranging the necessary switching gear to electrically energise the crossing for the respective line as required and instead just have the whole thing neutral...? Thence all that needs to be "taken care of" is the challenges of mechanically conveying the pantograph from one side to the other.

 

[Bald Rick]

It is absolutely not a problem electrically. It is exactly the same principle as any diamond crossing of which there are countless examples on the network. It is straightforward to keep everything segregated (if that is actually required, which is unlikely)

The issue is the pantograph. The pan head, in contact with the contact wire, needs to cross another two contact wires almost at right angles. Therefore the other contact wires must be at exactly the same height, which means they must be connected. Tensioning this arrangement conventionally is impossible - if the wire moved longitudinally (for any reason, but typically temperature), then it would pull the ‘perpendicular’ contact wires out of registration.

Therefore some arrangement is necessary that fixes the wires firmly in position, and the best way to do that is with conductor bar. The crossing itself, and a short distance either side on all approaches would be one section, isolated from the normal sections by in line section insulators.

 

[edwin_m]

Is there anywhere overseas where electrified lines cross each other with trains on at least one allowed a reasonable speed? In the Rome example I gave, I doubt anything gets above 10km/h.

 

[pdeaves]

As a matter of side interest, the Dublin tram system has two 'one track crossing two tracks' flat crossings in the city centre.

 

[Bald Rick]

Is there anywhere overseas where electrified lines cross each other with trains on at least one allowed a reasonable speed? In the Rome example I gave, I doubt anything gets above 10km/h.

There’s a famous set of flat crossings in Nagpur, India. Plenty of videos on YouTube. Not high speed though (perhaps 30 km/h) and locos drop their pantograph.

 

[Class 170101]

Therefore some arrangement is necessary that fixes the wires firmly in position, and the best way to do that is with conductor bar. The crossing itself, and a short distance either side on all approaches would be one section, isolated from the normal sections by in line section insulators.

Will the presence of Newark East Chord and its respective junctions being so close also be a factor in the design of the OLE.

Would it not be easier and cheaper quite frankly to install a flyover the next time Newark Flat Crossing is up for life expiry?

 

[HSTEd]

Would it not be easier and cheaper quite frankly to install a flyover the next time Newark Flat Crossing is up for life expiry?

As I recall the requirement for freight leads to the flyover having to be an absolutely enormous structure.

 

[Malcmal]

https://goo.gl/maps/7TgZCPGSWyb3STJE9

From Google maps in the centre of Helsinki on the tram network - a nice example of OHL crossing at 90 degrees. Funny I never thought about the logistics of it until I saw this thread.

 

[AlbertBeale]

https://goo.gl/maps/7TgZCPGSWyb3STJE9

From Google maps in the centre of Helsinki on the tram network - a nice example of OHL crossing at 90 degrees. Funny I never thought about the logistics of it until I saw this thread.

What's even more fun is where you get trams and trolleybus wires crossing one another (given they do different things, both electrically and mechanically); I nearly missed a train in Linz once, stopping on the way to the station to look at a junction like that and figure out what was going on with the network of wires above my head, and how it worked...

 

[Bald Rick]

Will the presence of Newark East Chord and its respective junctions being so close also be a factor in the design of the OLE.

Would it not be easier and cheaper quite frankly to install a flyover the next time Newark Flat Crossing is up for life expiry?

It definitely would not be easier and cheaper to build a flyover!

 

[Dr Hoo]

What's even more fun is where you get trams and trolleybus wires crossing one another (given they do different things, both electrically and mechanically); I nearly missed a train in Linz once, stopping on the way to the station to look at a junction like that and figure out what was going on with the network of wires above my head, and how it worked...

Ghent in Belgium used to have that. I tried to photograph it against the backdrop of the intricately carved grey stonework of the adjacent church on a dull day. Totally impossible to work it out.