Pendelino Pantograph questions

[CosherB]

1) Pendelinos have two pantographs (linked by 25KV cables over the coach roofs), only one of which is raised in service. How is it decided which one to use? Do they always use the trailing one, the leading one, or could it be either?

2) Given that you need a clearance of several feet from a 25KVoverhead line to prevent flash-over, how can 25KV be routed along Pendelino coach roofs without breaking through the cable insulation to flash-over to the coach body?

CC

 

[mbonwick]

I believe (probably wrongly) that the trailing panto is normally used for aerodynamic purposes, although the front one could be raised if required.

As for 2, I've no idea

 

[Tom]

Leading panto is always up, unless that has a fault, in which case the trailing panto is raised.

As for the latter, no idea, again.

 

[CosherB]

Leading panto is always up, unless that has a fault, in which case the trailing panto is raised.

As for the latter, no idea, again.

Thanks Tom. Any idea why it's the leading one that's used in preference to the trailing one?

CC

 

[Tom]

There is a technical reason I'm sure, but you'd be better off asking someone more in the know!

 

[Turbostar]

I've noticed it in TGV's as well, the 1st/leading power car has it's panto up, if another set is attached the leading power car of that set has it's panto up as well. Same with Eurostars I believe as well. As to why, I don't know.

Mart

 

[westcoaster]

2) Given that you need a clearance of several feet from a 25KVoverhead line to prevent flash-over, how can 25KV be routed along Pendelino coach roofs without breaking through the cable insulation to flash-over to the coach body?

CC

sorry i dont quiet get what you mean. * put's thinking cap on * in my eperience the 25kv goes down through the train and runs along the bottom through the coach's to were it is needed,

 

[Guinness]

As Tom said the Leading Pantograph is always used unless there is a fault with it. If the rear Pantograph is needed then the driver needs permission from the Maintenance Gang before it can be raised.

Bit confused of what your asking for number 2. :?

 

[1VWC]

There is a technical reason I'm sure, but you'd be better off asking someone more in the know!

There is no technical reason for the front one being used in preference.

The original plan was to use the trailing pantograph as, if this was damaged for whatever reason, the front one would have passed underneath whatever was causing the damage without being affected.

It has been put to me by a couple of drivers that the powers that be decided to use the front pantograph for visual reasons (i.e. looks unusual having the rear pantograph up).

 

[CosherB]

sorry i dont quiet get what you mean. * put's thinking cap on * in my eperience the 25kv goes down through the train and runs along the bottom through the coach's to were it is needed,

On the Pendolino the two coaches with pantographs (which are unpowered and which each contain the main transfromer) are linked by coach-top cables. That's how one pantograph powers both halves of a Pendelino set (each set being made up of two 4-coach units back-to-back, with the ninth unpowered coach in between).

My question is (and I'm having difficulty expressing in any simpler terms than I already have) is how is 25KV routed along the train roof, even in insulated cables, without flashing over to the coach roof itself (which is made of metal at ground potential)?

CC

 

[class 313]

I would like to say first,

its PENDOLINO...

1) I do believe its the pantograph closet to the leading driving cab that is used...

2) I don't know

Also...

You left with CC when your username is Captain Speaking... So shouldn't it be CS?

 

[tramboy]

I was always lead to believe (apologies for moving slightly off topic), that on Eurostar, both pans, leading and trailing, had to be raised to counterbalance the effect that a fast travelling train has on overhead...ie the fact that the front pan causes a wave to start on the contact wire and is then rapidly damped by the rear pan. This, mind, only happens on Eurostar, as the standing wave is sufficiently damped between the front and rear pans for both to get contact.

On TGV sets, only the rear pantograph is raised, avoiding amplification of the oscillations created by the front pantograph, as the tension in teh overhead on LGVs is higher than normal. However, on the old classic lines, slower running means no standing wave is created, and so both pans are up.

Hope that helps..

Dave

 

[ChrisCooper]

On the Eurostars, both Pantographs are used since the 2 powercars together draw too much power for one pantograph to cope, and also there in enough distance between them for the waves in the overhead to have died. There is still a lot of arcing from the rear pantograph though. When TGVs are run together, they also have 2 pantographs raised. I think the front and rear of the complete set are used, to give most seperation. In the UK, high voltage power lines between coaches was always against the rules (the Pendolino was the first to get this changed), and this, plus problems with high speed current collection from the rear pantograph, was why the APT had 2 powercars in the centre, since the high voltage link was only between them, and didn't go near passenger vehicles. Oviously, this was less than ideal, so a production APT would have had a none tilting powercar at one end end a DVT at the other. In the end, this design, without articulation and with an independant loco rarther than a powercar (although it's still basically a APT powercar with a cab at each end) became the Intercity 225.

 

[westcoaster]

On the Pendolino the two coaches with pantographs (which are unpowered and which each contain the main transfromer) are linked by coach-top cables. That's how one pantograph powers both halves of a Pendelino set (each set being made up of two 4-coach units back-to-back, with the ninth unpowered coach in between).

My question is (and I'm having difficulty expressing in any simpler terms than I already have) is how is 25KV routed along the train roof, even in insulated cables, without flashing over to the coach roof itself (which is made of metal at ground potential)?

CC

i think the cable your on about looks like a twizler above the corridor connections, the cable is not big enough to carry 25kv it must be for other stuff, im 90% sure the power is distubuted underneath the carriages using a cable that normally is attatched under the coupling system between the carriages.

 

[yorkie]

Yep, it certainly won't be 25kV through the coaches. The electricity is converted by the transformer from 25kV to a lower voltage, and it is at the lower voltage that the electricity is passed through the train.

So, the answer to question 2), "how can 25KV be routed along Pendelino coach roofs"; it isn't

 

[class 313]

I do believe the the wire above the coach is for connecting the coaches electronically, if you get me. I mean, announcements in all coaches and such...

 

[mbonwick]

I understand, class 313

 

[CosherB]

So, the answer to question 2), "how can 25KV be routed along Pendelino coach roofs"; it isn't

It is, actually.

Each Pendelino is two 4-coach units coupled back to back, with a non-powered coach between, making 9 coaches in all. Virgin are hoping to add another centre unpowered coach, which will strenghten the trains to 10 coaches.

In each 4-coach unit, the first coach (which includes the drivers cab), the second coach, and the fourth coach each have two underfloor traction motors which drive the inner pair of wheels on each bogie through drive shafts, so each unit has 6-axle (12 wheel) drive, 12-axles (24 wheel) drive for the whole train.

The third coach in each unit is unpowered, but carries the pantograph and main transformer for that unit. The 25KV traction current is carried between these 'transformer' coaches via a roof-top high voltage bus across the three interveneing coach roofs (according to the 'pendelino' supplement' that came with Railway Magazine a while ago), so either pantograph can supply power for both Pendelino 'units' (Pendos only use one panto at a time).

Pendolino manufacturer had to prove special safety case to health & Safety Executive to have this approved.

CS

 

[Guinness]

You've basically answered your own question then....

FWIW, Pendolino have a through power connection throughout the whole train whether it's a Unpowered Trailer or not. They're not 4 Car Trains with a TSO and another "4-Car Set" stuck together.

 

[CosherB]

You've basically answered your own question then....

No! All I've done is described the arragement to connect the two 'transformer' cars with a 25KV link across the roofs of the 3 intervening coaches (it goes no further - not the lenght of the train - why should it? it's only there so 1 panto can supply 25KV to both transformer cars).

My question is - technically, how is a voltage as high as 25KV safely contained so close to the coach bodywork, without flashing over to the coach body. It obviously is, but I don't understand the physics of how it's done. It's that that I'd like to know.

Maybe I should post this one on a science forum rather than a rail forum.

CS

 

[Sprog]

Im doing electrical theory at the moment in college for my Aprenticeship.

We are currently studying cable types coincidently.

From what i have seen, the 25kV bus cable at roof level is made from rather thick and heavy duty cabling.

I should imagine is it extremely high-grade cable, with a stranded copper/aluminum conductor, surrounded by Oil-impregnated paper insulation, plus armouring of somesort and then a few layers of PVC Insulation and an external sleeving.

At the Corrdior connections, it appears to be mounted on Insulators and then the Cable section between the two coaches is 'flexi', so that probably uses cables of the same grade, minus the Paper and such thick armouring.

Oh, and to Yorkie and co, it is DEFINATLY a 25kV bus bar and as CS said, Alstom/Angel had to do alot of paperwork to get the safety case for it approved as it was a first for the UK.

HA!

EDIT: Corrected typos - apologies, it had been a long day

 

[CosherB]

Thanks Sprog. :thumbup:

CS

 

[Turbostar]

Im doing electrical theory at the moment in college for my Aprenticeship.

We are currently studying cable types coincidently.

From what i have seen, the 25kV bus cable at roof level is made from rather thick and heavy duty cabling.

I should imagine is it extremely high-grade cable,with a stranded copper/aluminum conductor, surrounded by Oil-inmpregnated paper insulation, plus armoring of somesort and then a few layers of PVC Insulation and an external sleeving.

At the Corrdior connections, it appears to be mounted on Insulators and then the Cable section between the two coaches is 'flexi', so that probably uses cables of the same grade, minus the Paper and such thick armouring.

Oh, and to Yorkie and co, it is DEFIINATLY a 25kV bus bar and as CS said, Alstom/Angel had to do alot of paperwprk to get the safety case for it apprioved as it was a first for the UK.

So what about the Eurostars, that are based on the TGV design, as they have the same sorta thing, like TGV's, in between coaches at roof level?

Mart

 

[Sprog]

So what about the Eurostars, that are based on the TGV design, as they have the same sorta thing, like TGV's, in between coaches at roof level?

Mart

Yes.

 

[16CSVT2700]

So what about the Eurostars, that are based on the TGV design, as they have the same sorta thing, like TGV's, in between coaches at roof level?

Mart

I believe he means a first in the UK for general/regional services.

 

[ChrisCooper]

I don't know if the Eurostars do, since they would never run without both pantographs raised, as the current would be too high (remember, a Eurostar is about the same length as, and draws similar power to, a pair of TGVs). TGVs though run with the rear powercar's pantograph raised, with the front being supplied by a 25kV power line. The only train in the UK other than the Pendolino where 25kV has been sent between carriages was the APT, but this was only between the two adjacent powercars.

 

[Guinness]

No! All I've done is described the arragement to connect the two 'transformer' cars with a 25KV link across the roofs of the 3 intervening coaches (it goes no further - not the lenght of the train - why should it? it's only there so 1 panto can supply 25KV to both transformer cars).

My question is - technically, how is a voltage as high as 25KV safely contained so close to the coach bodywork, without flashing over to the coach body. It obviously is, but I don't understand the physics of how it's done. It's that that I'd like to know.

Maybe I should post this one on a science forum rather than a rail forum.

CS

A-ha, I've misinterpreted the question! Apologies Sir!

Sprog has the answer and couldn't of explained it any better. The 25kHz is basically stepped down power wise into a lower voltage. The transformers on the roof does the job to convert it into a safe enough voltage to be passing through the trains. High enough to power the underfloor Motors on 8 of the Motor Coaches. It does however pass through the entire length of the train as explained in my previous post. The cables are in the top right and a left corners of the side of the coach and have Yellow Warning Panels next to them. The Corridor Connectors also have the Air Pipes, Main Res, Electrical Equipment for PA and other equipment and of course the coupling.

 

[thefab444]

Each Pendelino is two 4-coach units coupled back to back, with a non-powered coach between, making 9 coaches in all. Virgin are hoping to add another centre unpowered coach, which will strenghten the trains to 10 coaches.

A little OT, but whats the betting this extra coach will be FC, or a Composite?

 

[Guinness]

The extra coach that made Pendolinos 9-Car was a TSO (Trailer Standard Open). No Motor or Disabled Toilet and has 72 Seats.

 

[O L Leigh]

Eurostars need to run with both pans raised because there is no "bus" connection between the power cars at each end. This is because the safety requirements for the Channel Tunnel are more strict than those for National Rail. Therefore, each end of a Eurostar has to collect it's traction current independently. It doesn't cause too much aggro when running off the OLE, but it can make life tricky when running off the juice rail because of the number, spacing and length of the gaps.

To address the original questions, I believe that the reason why Pendolinos run with only one pan raised is to do with what happens where the pan meets OLE at high speed. As I understand it, the worry is that the leading pan would set up sway in the wires that would not be sufficiently dissipated before the second pan comes along. This would mean that the second pan could suffer from unacceptable levels of "pan bounce" and could even cause a dewirement. Why it's the leading pan that raises and not the trailing one, I imagine that this is just down to the way that the TMS computer is configured.

As to the second question, unless someone knows for certain, I'd be very surprised if the Pendo's have a 25kV "bus" connecting both ends of the unit. Not wishing to undermine Sprog, but he seems as certain about the Pendolino as he is about the Eurostar, and yet he is wrong about at least one of these (sorry).

Pendolino's may comprise two "self-contained" 4 car units with an intermediate trailer, but they are still through-wired as a single unit and I'd be very surprised if they worked in any way differently to most other EMU's. I would expect that a single transformer would be adequte to step the 25kV from the overheads down to the various voltages required by the on-train systems before distributing them to the entire unit. This would be far safer and cheaper than having to run two transformers in different parts of the train from just a single pan by means of a 25kV "bus". After all, if electrical current at whatever voltage is required by the traction motors is being sent between coaches even within each 4 car "sub-unit", why not send it the entire length of a 9 car unit...?

one TN