Why was the newcastle metro created as 1.5kv dc powered not 25kv ?

[zwk500]

1500V is a comparatively simple conversion from 750V equipment.
It's all low-ish voltage DC so conceptually you can just connect pairs of motors in series instead of parallel.

Indeed. Under a similar principle it's why 3KV trains regularly run onto 1.5KV lines, such as Belgium-NL or Italy-France.

It's a much less involved process than building a 25kV train would be.

Absolutely. Especially for a metro.

 

[swt_passenger]

1500V is a comparatively simple conversion from 750V equipment.
It's all low-ish voltage DC so conceptually you can just connect pairs of motors in series instead of parallel.

The existing Metro units do have 2 x 750V motors in series, it’s not just conceptual!

 

[HSTEd]

The existing Metro units do have 2 x 750V motors in series, it’s not just conceptual!

I didn't want to say that without hard evidence to hand!

 

[swt_passenger]

I didn't want to say that without hard evidence to hand!

I saw a pretty good circuit diagram in a RAIB report else I’d never have known either…

 

[AM9]

The existing Metro units do have 2 x 750V motors in series, it’s not just conceptual!

Just like the Manchester-Glossop class 506 (and their siblings the GE class 306 which were originally powered from a 1500VDC OLE*), the four DC traction motors were configured as two pairs of series connected 750V types.
* The configuration was retained even after their conversion to 25Kv ac as they ran from a rectified ac 1500v DC bus.

 

[DanNCL]

I think there’s an under explored potential for a larger 1500V DC network in the North East. Now that Metro, including the Durham Coast shared section, is stuck with it for another 40 years, I think it would make sense to wire the whole of the Durham coast from Gateshead to Norton Junction with 1500V DC.

The battery solution might work for passenger stock but it’ll never be viable for freight and diesel freight is unlikely to be allowed to last another 40 years. So that ultimately means a UK dual voltage freight loco would be needed.

I don’t know whether 1500V DC electrification on Teesside too would be viable or if 25kV AC would be better there. There’s the argument that if dual voltage stock has to be procured for the Durham Coast anyway, you might as well utilise it and save money with DC electrification on Teesside.

Interestingly there is already provision for Nexus to charge freight operators for use of the 1500V DC overhead on the Jarrow branch, albeit they’ve noted they don’t currently anticipate any such usage by freight operators.

 

[AM9]

Interestingly there is already provision for Nexus to charge freight operators for use of the 1500V DC overhead on the Jarrow branch, albeit they’ve noted they don’t currently anticipate any such usage by freight operators.

Surely any power on offer would be inadequate for serious freight use, - especially at 1500V for which the OLE is probably designed only to satisfy modest passenger stock demand.

 

[zwk500]

Surely any power on offer would be inadequate for serious freight use, - especially at 1500V for which the OLE is probably designed only to satisfy modest passenger stock demand.

The voltage isn't particularly important - France and Netherlands have extensive 1,500v networks and haul plenty of freight around, but you are correct that the power supply is unlikely to be useful to freight. Last-mile batteries are much more likely to be the solution for freight operators.

 

[AM9]

The voltage isn't particularly important - France and Netherlands have extensive 1,500v networks and haul plenty of freight around, but you are correct that the power supply is unlikely to be useful to freight. Last-mile batteries are much more likely to be the solution for freight operators.

The voltage isn't important from a safety PoV but the lower the voltage, the higher the current for a given power, - indeed, with a 25Kv supply, the OLE carries 40A per MW. The same power on a 1500V system would be 667A. Therefore instead of the 160A that a typical electric freight loco (class 88) might require from a 25kV OLE, which is well within almost every ac OLE installation in the UK*, the 1500V DC OLE would need to provide 2668A.
At the moment, a pair of 2-car NEXUS class 599s can draw up to 933A whereas the new 5-car class 555s are slightly more efficient with a maximum continuous draw of 880A, so the exisiting OLE and its supply will be able to provide for a similar number of the new trains with a greater capacity. To cater for typical electric freight trains, there would need to be a considerable amount for reinforcement of the supply and OLE, - possibly installing new compound catenary which has additional support for a much heavier conductor wire. I doubt that the additional revenue from electric freight.

 

[zwk500]

I doubt that the additional revenue from electric freight.

I agree, any possible revenue from electric freight won't cover the investment required.

 

[SeanG]

I would imagine that the solution for any new units going forward would be 25kv with batteries to cover the non electrified & 1.5kv sections.
As has been said, last mile or battery locos such as 88s or 93s could cover anything off the 25kv

 

[Meerkat]

If you were electrifying the Durham Coast Line would you bother continuing to run Metro along it?

 

[zwk500]

If you were electrifying the Durham Coast Line would you bother continuing to run Metro along it?

Probably, because the Metro will offer a much more attractive service to people travelling into Newcastle itself than the national rail could ever sensibly provide, frequency and stop location wise.

 

[DanNCL]

If you were electrifying the Durham Coast Line would you bother continuing to run Metro along it?

Yes for a variety of reasons. As already mentioned it will always be a more attractive service than an inevitably less frequent mainline service would be. Additionally there’d be massive political resistance from all parties to any move to stop running Metro to Sunderland.

In any case the line is needed to provide terminating capacity from Gosforth - Metro runs 20tph through the core during the peak and South Shields can only handle 5tph (6tph doable with a timetable recast), so without the Sunderland line you’d be trying to turn back 15tph at Pelaw, probably just about doable but it’d be tight.