East Coast Class 91s

[Whistler40145]

With East Coast planning a refurbishment programme for it's Class 91 fleet.

I have read in a Railway publication that top & tail 91s are to be used as a testbed for the InterCity Express Project, is this to ascertain any problems with 2 91s drawing power at the same time?

 

[Aictos]

With East Coast planning a refurbishment programme for it's Class 91 fleet.

I have read in a Railway publication that top & tail 91s are to be used as a testbed for the InterCity Express Project, is this to ascertain any problems with 2 91s drawing power at the same time?

Similar tests were done in 2009 which were a complete success according to one of the drivers booked to drive the test train.

There must be a reason though for it though.

 

[DarloRich]

something to do with pantograph testing i think ( cant recall WHAT exactly!)

 

[gordonthemoron]

IIRC UK trains don't run with more than one pantograph up, even if they are fitted, e.g. Pendo. However that is not the case in other countries

 

[Whistler40145]

Is it that in other countries the Power Supply can cope with it?

 

[MCR247]

No, as it wouldn't draw twice as much power I don't think?

 

[Whistler40145]

Thanks, I was being a bit thick!

 

[jopsuk]

Presumably it's more to do with the effect on the OHL than the power draw- i'd have thought it's not uncommon for more than one 91 to be in the same power section.

Slower trains (up to 100mph) commonly run with multiple pantographs up as they have to, as autocouplers don't have traction power connections. Three pantographs is everyday on the LTS, GE, ECML (GN services) and WCML and is being introduced on the MML and WAML.

 

[gordonthemoron]

I think it is the OHL tension, DB ICEs run with two pantographs up if they're running in multiple, the banging caused by this when entering a tunnel at high speed is quite loud

topped and tailed ICs also run with both pantos up

 

[rail-britain]

IIRC UK trains don't run with more than one pantograph up, even if they are fitted, e.g. Pendo. However that is not the case in other countries

Loads of trains do, currently and in the past
Obvious one is the pair of Class 86, 87, and 90
Next are the multiple EMUs, such as pairs of Class 321, 350, and so on
All of these generally increase the electrical demand

Usually the planners make sure the number of such multiple trains do not exceed the available power supply in that area
This used to be the case with pairs of Class 86/87/90 between Carlisle and Mossend, such that there were limits on how many could operate

 

[Maxfly]

is it not something to do with cuasing the OHL to kind of 'ripple and when it then hits the second pantograph it has a higher risk of bringing down the wiring?? sure i read something about that?!?!

 

[Barrett M95]

North of London Eurostars ran on ECML with both pans raised at 125mph.

 

[cj_1985]

North of London Eurostars ran on ECML with both pans raised at 125mph.

but how far apart were the pantographs though....!

 

[Barrett M95]

is it not something to do with cuasing the OHL to kind of 'ripple and when it then hits the second pantograph it has a higher risk of bringing down the wiring?? sure i read something about that?!?!

The second pan head will always have a harder life keeping contact but this won't increase the chance of bringing wires down unless the alignment is way off and high winds are blowing but in such a case it is really no more likely to get into trouble than a single pan.

When TGV sets run in multiple on LGV there is only 200m between pan heads at up to 320km/h.


--- old post above --- --- new post below ---

but how far apart were the pantographs though....!

280m.

TGV on classic lines in France run with all four pans up at 200+km/h including the inner adjacent power cars. And the OHLE is older and less sophisticated than that on ECML. It is 1.5kV DC and is chunkier wire but the tension is very low.

 

[Whistler40145]

I don't wish to appear thick, but why can several EMUs draw power together, but 91s working in top & tail mode can't, it doesn't seem logical to me.

 

[ainsworth74]

Because the locomotives draw much more power than a EMU. Whilst I don't have access to how much the actual draw is I can tell you for example that two 91s have a combined power output of 9400kW whilst three 365s have a power output of only 3768kW. So it's a fair assumption that the 91s are drawing far more power than the three 365s simply because they output so much more.

 

[Whistler40145]

Thanks.

 

[NightatLaira]

I don't know if this is an 'old wives tale' but someone once told me that when two electric engines are top and tailed on the same train with both pantographs up and drawing power at full pelt in the same section, the section of catenary between the two pantographs is effectively void of electricity? Is this true - can anyone with a better understanding of electrics refute, explain or expand upon this?

 

[cj_1985]

The second pan head will always have a harder life keeping contact but this won't increase the chance of bringing wires down unless the alignment is way off and high winds are blowing but in such a case it is really no more likely to get into trouble than a single pan.

When TGV sets run in multiple on LGV there is only 200m between pan heads at up to 320km/h.


--- old post above --- --- new post below ---


280m.

TGV on classic lines in France run with all four pans up at 200+km/h including the inner adjacent power cars. And the OHLE is older and less sophisticated than that on ECML. It is 1.5kV DC and is chunkier wire but the tension is very low.

ISTR being told that the OHLE on the ECML was done on the cheap*... never thought i'd hear that the ECML OHLE was "sophisticated"

* Same with the GEML iirc

 

[Barrett M95]

ISTR being told that the OHLE on the ECML was done on the cheap*... never thought i'd hear that the ECML OHLE was "sophisticated"

* Same with the GEML iirc

We have had this discussion many times. I am a rolling stock engineer but another of our members - Old Timer, is an infrastructure engineer and explains the ECML myth here: http://www.railforums.co.uk/showthread.php?t=48804&page=2

In any case it is a relative term. If you had seen the sag, and poor tension on some of the lines in southern France and Belgium that are on lines rated at ~200km/h you would realise what I mean!

 

[hairyhandedfool]

I don't wish to appear thick, but why can several EMUs draw power together, but 91s working in top & tail mode can't, it doesn't seem logical to me.

There is a speed restriction for certain types of electric stock, 319s, for example, were/are restricted to 75mph when running as a 12 car train with three pans up. A 12 car 319 train with one pan locked down (ECS only) and two pans up can travel at linespeed (upto 100mph).

 

[Aictos]

North of London Eurostars ran on ECML with both pans raised at 125mph.

Actually I'm quite sure they never did that, They were actually restricted to 110mph mainly because they were so power hungry.

 

[Barrett M95]

Initially yes but the restriction was lifted and they ran at 125 south of Grantham for 2 or 3 years.

 

[Whistler40145]

Is this problem less evident in France, Germany & other large European countries whereby the power stations & infrastructure are far superior?