Capabilities of Network Rail Series 1 OLE (speed)?

[ainsworth74]

I recently had a trip between Reading and Didcot for the first time since the OLE has been put up and basically finished there. It certainly makes for an impressive sight!

It did, however, make me thing about the capabilities that Series 1 may have beyond those advertised. Particularly in reference to the maximum speed it can be used for in regularly day to day operations.

Now as far as I'm aware Series 1 has been designed from the outset to be used at 140mph so that gives us our starting point but I'm wondering if there is scope for going beyond that?

I believe, to take a historical example, BR managed to develop its Mk3 OLE from being used for 100mph operations to 125mph for the ECML. Now we can argue about how successful that was but still broadly speaking they managed squeeze out more performance from their existing design.

Could Network Rail do something similar with Series 1?

Note: I'm well aware that there is little to no need for this because its highly unlikely any Series 1 installation will ever need speeds in excess of 140mph but I thought it would be interesting to think about from a purely hypothetical stand point.

 

[AM9]

I recently had a trip between Reading and Didcot for the first time since the OLE has been put up and basically finished there. It certainly makes for an impressive sight!

It did, however, make me thing about the capabilities that Series 1 may have beyond those advertised. Particularly in reference to the maximum speed it can be used for in regularly day to day operations.

Now as far as I'm aware Series 1 has been designed from the outset to be used at 140mph so that gives us our starting point but I'm wondering if there is scope for going beyond that?

I believe, to take a historical example, BR managed to develop its Mk3 OLE from being used for 100mph operations to 125mph for the ECML. Now we can argue about how successful that was but still broadly speaking they managed squeeze out more performance from their existing design.

Could Network Rail do something similar with Series 1?

Note: I'm well aware that there is little to no need for this because its highly unlikely any Series 1 installation will ever need speeds in excess of 140mph but I thought it would be interesting to think about from a purely hypothetical stand point.

Given that the substantial gantries and cantilever structures leave very little hardware to flap in the breeze, it seems that higher speeds could well be tolerated albeit with a reliability/maintenance tradeoff. The lack of the 'cats cradles' that headspans are together with the short supports from gantries not only reduces the high voltage footprint but also give the system higher rigidity and probably offer opportunities for increased tension to reduce the impact of standing waves where multiple pantographs are used.

 

[GRALISTAIR]

As AM9 says about multiple pantographs - I am sure there could be a stipulation such as " if in single pantograph mode a line speed of 140 + xyz is permitted " or words to that effect

 

[QueensCurve]

Given that the substantial gantries and cantilever structures leave very little hardware to flap in the breeze, it seems that higher speeds could well be tolerated albeit with a reliability/maintenance tradeoff.

The problem is not just flapping in the breeze, it is that the leading pantograph sets up a standing wave in the wire which causes periodic loss of contact at the trailing pantograph.

This is why the French TGV (and UK Pendolino) approach is to have a 25kV bus on the roof of the train so that only one pantograph need be used.

The Brecknell-Willis/BR pantograph which is now the UK standard was intended to deal with the standing wave problem as I understand it.

 

[AM9]

The problem is not just flapping in the breeze, it is that the leading pantograph sets up a standing wave in the wire which causes periodic loss of contact at the trailing pantograph.

Which is what I was referring to when I said:

... but also give the system higher rigidity and probably offer opportunities for increased tension to reduce the impact of standing waves where multiple pantographs are used.

Yes I know that 25Kv busbars are there to obviate the need for multiple pantographs. However, that is sometimes an operational inconvenience where shorter trains are split/joined in service (e.g. as the class 800/801s maybe because of the 'long thin' traffic route to the southwest), so having a more taut conductor with reduced play raises the resonance and limits off-centre movement, giving even single pantographs a more reliable environment.

The Brecknell-Willis/BR pantograph which is now the UK standard was intended to deal with the standing wave problem as I understand it.

Which it does a lot better than the earlier Stone Faiveley and AEI cross-arm pantograph designs but the design is still mechanically passive so there are conditions under which it is not foolproof. Maybe in the future it may have active aerodynamics. Until then, the OLE can be optimised to give the pantograph the best chance of reliable operation.

 

[Domh245]

This is why the French TGV (and UK Pendolino) approach is to have a 25kV bus on the roof of the train so that only one pantograph need be used.

The AT300s produced thus far all have a 25kV bus on the roof. The multiple pantographs issue is for when you are running two short sets coupled together (because passing 25kV through a coupler is pretty impractical)

 

[najaB]

The multiple pantographs issue is for when you are running two short sets coupled together (because passing 25kV through a coupler is pretty impractical)

It's not an insoluble problem though. It would require a new coupler design with a separate socket/plug equipped with appropriately heavy pins to carry the large current flow. I don't know if I'd trust it 100% as an automated setup though.

 

[AM9]

It's not an insoluble problem though. It would require a new coupler design with a separate socket/plug equipped with appropriately heavy pins to carry the large current flow. I don't know if I'd trust it 100% as an automated setup though.

It's not the current that is the problem, - for instance, a 5000hp traction plus hotel feed would be well under 200A, not that difficult with advanced connectors. Maintaining a high voltage through a demountable connector, manually or automatiaclly mated would be an operational nightmare. It could go through the cycle more than 5 times per day with half of the intervening time spent exposed to the elements. That would be a lot more expensive to provide and maintain than a well engineered OLE.

 

[gsnedders]

This is why the French TGV (and UK Pendolino) approach is to have a 25kV bus on the roof of the train so that only one pantograph need be used.

TGVs frequently run in pairs, though, and that does require two pantographs (though I think I have some memory of them using the two at the extremes hence being around 400m apart?).

 

[BahrainLad]

TGVs frequently run in pairs, though, and that does require two pantographs (though I think I have some memory of them using the two at the extremes hence being around 400m apart?).

Eurostar has no 25kv bus due to the tunnel safety regulations but as the two power cars are 750m apart using two pantographs is standard practice.

 

[Senex]

TGVs frequently run in pairs, though, and that does require two pantographs (though I think I have some memory of them using the two at the extremes hence being around 400m apart?).

The rule for German ICE2s certainly used to be that when they were in multiple they could only run at 250 if the two pantos were at the outer ends.

 

[Bald Rick]

Eurostar has no 25kv bus due to the tunnel safety regulations but as the two power cars are 750m apart using two pantographs is standard practice.

750m?

 

[gsnedders]

750m?

Yeah, that's definitely wrong given they're only 387m long to start with! They're comparable to the 2x200m TGVs in length, hence similarly using two pantographs is similarly not a problem on the LGV.