Overhead wires

[STEVIEBOY1]

I Do wonder if 3rd rail is better as I hear so many times that trains are delayed, cancelled etc owing to over head wires coming down, either due to high winds or being pulled down by the pick up equipment on the trains or locos, this seems especially bad in east anglia, the ECML and around Bletchley. I know in the winter the 3rd rail does Ice up sometimes, but that does not seem to happen so often. ( I wonder too why when they electrified the East Grinstead Line, the did not also do the Uckfield Branch and the Ashford-Hastings line when Ashford was set up Eurostar).

 

[ole man]

I noticed there are odd sections of the ECML where there are two single masts on each side with the triangles on.

Hard to explain what I mean but take a look at this picture from Tamworth on the WCML. Its an old pic but shows the mast setup I mean.

http://www.trainspots.co.uk/100-199/tamworth/tamworth_4.jpg

Couldn't the ECML have applied this principle? That way only two supports required and no top bar.

There called Cantilevers, and are a lot stronger than Headspans, but they are used mostly in two track sections, there are places where there are back to back Cantilevers.
Headspans if maintained work ok, but suffer from wind and movement problems,also in hot and cold wheather they either tighten or slacken, the main problem with them is that if one road is damaged the whole section needs to closed to able linesmen to work on them safely.

Headspans will never be used in this country again, unless it is a like for like replacement.

 

[Nym]

Would I be right in thinking that the ground supports for headspans would not be strong enough to support a chunk of steel slung between them in place of the headspans?

Headspan supports don't look strong enough to take a full steel support cantry (as in your avatar) so I'm assuming that unless you replaced the whole support set (by this time you may as well re-electrify) theres no simple 'upgrade' for headspans. Unless one can come up with a simplified autotensioner system to keep them closer to tensioned correctly, but then a CBR would need almost every de-wirement to be as a result of headspan tension and for these to cost a hell of a lot of money.

 

[ole man]

Yes you would be correct, also the masts are not compatible to fit a boom on top, each mast is different in how far it is sank, and which type of support needed, either concrete or straight piling, depends on ground conditions, weight on the structures.

Headspans as said many times are a cheap easy fix, changing the span wires to copper/steel mix has helped, as most of the span wires are now life expired.
The masts would be able to cope with a simple Cantilvever on the back if say a new road was being installed

 

[NSEFAN]

I Do wonder if 3rd rail is better as I hear so many times that trains are delayed, cancelled etc owing to over head wires coming down, either due to high winds or being pulled down by the pick up equipment on the trains or locos, this seems especially bad in east anglia, the ECML and around Bletchley. I know in the winter the 3rd rail does Ice up sometimes, but that does not seem to happen so often. ( I wonder too why when they electrified the East Grinstead Line, the did not also do the Uckfield Branch and the Ashford-Hastings line when Ashford was set up Eurostar).

3rd rail adds a lot more friction than overhead (so it limits the speed), and requires more substations to work. Mixing 3rd rail and overhead can be done, but it does cause additional complications. It's also one more risk to anyone on the line.

The best thing is to just do a proper job and install better quality wiring. A lot of money could be saved in the long term, as the infrastructure wouldn't keep falling over.

 

[ole man]

What do you mean by do a proper job?.
The wiring is installed to designs, the trouble with this country is the sheer volume of traffic and more importantly the whether
Human error does play a part in some cases, take the Neutral Section at Wembley that has been changed and fixed various times over the last few years yet it still causes problems, it is constantly taking a hammering .that is the problem

 

[NSEFAN]

What do you mean by do a proper job?.
The wiring is installed to designs, the trouble with this country is the sheer volume of traffic and more importantly the whether
Human error does play a part in some cases, take the Neutral Section at Wembley that has been changed and fixed various times over the last few years yet it still causes problems, it is constantly taking a hammering .that is the problem

My point was that better quality wires will cost more money initially, but if they fail less often then they are worth the investment (fewer delay minutes to worry about, for starters!). Obviously nothing is indestructible, but I'm convinced if more money was spent on better quality installations, then there would be savings to be gained in the long-term.

I was also responding to the suggested use of 3rd rail. My understanding is that overhead wiring is generally preferred to 3rd/4th rail, for the reasons in my previous post, so it would be pointless to install new 3rd rail, except where it is already installed and in underground networks. I'm happy to be corrected on these issues, though.

 

[LE Greys]

There called Cantilevers, and are a lot stronger than Headspans, but they are used mostly in two track sections, there are places where there are back to back Cantilevers.
Headspans if maintained work ok, but suffer from wind and movement problems,also in hot and cold wheather they either tighten or slacken, the main problem with them is that if one road is damaged the whole section needs to closed to able linesmen to work on them safely.

Headspans will never be used in this country again, unless it is a like for like replacement.

Hopefully not even then. When they wear out, they should be replaced by something stronger.

 

[1978NWUK]

What do you mean by do a proper job?.
The wiring is installed to designs, the trouble with this country is the sheer volume of traffic and more importantly the whether
Human error does play a part in some cases, take the Neutral Section at Wembley that has been changed and fixed various times over the last few years yet it still causes problems, it is constantly taking a hammering .that is the problem

There's no answer to why the neutrals at wembley keep failing, like you said in an earlier thread, they (NR) blamed contractors the first time but it was they themselves that installed the AF one that failed.

 

[yorksrob]

I Do wonder if 3rd rail is better as I hear so many times that trains are delayed, cancelled etc owing to over head wires coming down, either due to high winds or being pulled down by the pick up equipment on the trains or locos, this seems especially bad in east anglia, the ECML and around Bletchley. I know in the winter the 3rd rail does Ice up sometimes, but that does not seem to happen so often. ( I wonder too why when they electrified the East Grinstead Line, the did not also do the Uckfield Branch and the Ashford-Hastings line when Ashford was set up Eurostar).

the east grinstead line was part of scheme of progressive infill electrification on the southern region. Had network southeast continued in existance, it's highly likely that the uckfield branch and marshlink would have followed during the 1990s.

 

[CosherB]

3rd rail has many disadvantages to the extent that serious thought has been given to converting it to OLE. It cannot support high speeds or heavy current requirements, it ices up in winter, it requires (even with its much lower power capability) far more feeder stations, and it is dangerous to human and animal life.

It is barely able to support slow and light commuter EMUs in the south, never mind high speed Pendelinos taking many times the power of an EMU at much higher speeds.

 

[HSTEd]

Wasn't there some sort of campaign to fit third rail on the Royal Border Bridge prior to the development of low profile bridge gantries which consisted of two cantilevers with a tie bar between them?

As I said, the ECML wire is reasonably good quality, more important is that the ECML and other Mark III projects are extremely heavily used in comparison with many electrified routes on the continent.
This sort of wear and tear does tend to reduce reliability.

I would rather have two miles of Mark IIIB equipment than one mile of overengineered portal.

 

[PaxVobiscum]

To help you with the terminology of OHLE components and to give you some of the debate, analysis and commetary on the ECML structures, there's a few other threads already in this section - I'd be surprised if these didn't help you.

25KV OLE diagrams & support info ?

East Coast Overhead line

Limitations of British OLE

and perhaps also:
Our two electrification systems

Thanks for these links, DaveNewcastle.

In the third of these of these threads was a link to a fascinating video of an early electrification project Construction of the GE Electrification posted by OldTimer.
It reminded me of this short video about the Glasgow North Bank electrification I discovered some time ago
http://video.google.co.uk/videoplay?docid=1757694328470069217

Again, the safety aspects of the electrification train make for an interesting comparison with current practice.

 

[yorksrob]

3rd rail has many disadvantages to the extent that serious thought has been given to converting it to OLE. It cannot support high speeds or heavy current requirements, it ices up in winter, it requires (even with its much lower power capability) far more feeder stations, and it is dangerous to human and animal life.

It is barely able to support slow and light commuter EMUs in the south, never mind high speed Pendelinos taking many times the power of an EMU at much higher speeds.

The idea that the third rail is "barely able to support" "slow and light" commuter services is somewhat of an exageration. It's been supporting very dense patterns of heavily loaded twelve carriage commuter services for many years, some of which can get to reasonably high speeds.

The idea that it is somehow "dangerous" is also somewhat overstated, probably by the same sort of people who think that slam doors are inherantly dangerous.

It's not really suitable for the sort of very high speeds required by Inter-City type services though.

 

[HSTEd]

The idea that the third rail is "barely able to support" "slow and light" commuter services is somewhat of an exageration. It's been supporting very dense patterns of heavily loaded twelve carriage commuter services for many years, some of which can get to reasonably high speeds.

Including Eurostar, which I imagine is heavier than a twelve coach commuter train, especially with all its safety modifications.

 

[yorksrob]

Including Eurostar, which I imagine is heavier than a twelve coach commuter train, especially with all its safety modifications.

Indeed. I believe it definately drew more power then the slammers at the time they were introduced, however I'm not sure if it is the case with modern units.

 

[Eagle]

It's not really suitable for the sort of very high speeds required by Inter-City type services though.

I reckon you could just about get 110 mph out of some of the mainlines if you specced it up*; 444s could do it, perhaps.

*which probably includes adding a load more substations

 

[yorksrob]

I reckon you could just about get 110 mph out of some of the mainlines if you specced it up*; 444s could do it, perhaps.

*which probably includes adding a load more substations

Indeed. I suspect there aren't that many services on the Southern where such speeds would be practical due to timetabling anyway.

 

[Eagle]

Indeed. I suspect there aren't that many services on the Southern where such speeds would be practical due to timetabling anyway.

SWML long-distance services would certainly benefit (plus the raised speed limit could be used by Voyagers too).

 

[Mike C]

Indeed. I believe it definately drew more power then the slammers at the time they were introduced, however I'm not sure if it is the case with modern units.

We could only use a small percentage of full power when on 3rd rail network. If too much juice was demanded by the driver when the supply voltage was in the yellow, every 3rd rail powered train in the same section would grind to a halt because the section would be tripped. Happened once when I was tech riding. Drivers could only push the power controller forward a small amount when line volts were low. Very frustrating at times. It is reasons like that which in my mind are the main weakness in 3rd rail. That, winter icing and poor high speed current collection.

 

[Nym]

Aye, DC transmission in general like that can't handle voltage drops very well in high current draw situations, not like 25kv AC anyway where it tends to be (because of delivery methods) the frequency that suffers when too much current is being drawn, but since this is near directly connected to the national grid, there is a lot of inertia in the synchronous machines of the grid to help take up the slack.

Didn't know there was some kind of a warning system for low voltage on the DC lines though, perhaps this is something that NR should be monitoring to find the low voltage areas and do something about it by either improving or adding feeder stations???

 

[Mike C]

373 has a line voltage status on the drivers desk. Simple analogue scale with a needle inicating that green means you can give it full beans, yellow being reduce your demand or drive conservatively and red meaning coast only or if stopped, don't try and move.

Low volts on 25kV for us is something like 19.5kV. Gare du Nord is noted for having some very high spikes over 30kV. Only transient though.

 

[Nym]

One would think with the modern way we're now deploying motor controllers by using AC-DC-AC control and direct rectification into the DC Link that more modern AC equipment is much more resiliant to low or high voltages on the AC network than the older methods of AC control (Tap Changers, GTOs etc) but then I suppose that depends on how closely specified the rectifiers and invertors are, and even if there is a case of low voltage and this passing through, it wouldn't affecr and AC traction system that much, only reduce the amount of slip that can be supported within the windings. Would be intresting to see how these controllers have been specified for the newer units, 350 onwards (IGBT Based kit, rather than the GTO based SSCs)

 

[swt_passenger]

SWML long-distance services would certainly benefit (plus the raised speed limit could be used by Voyagers too).

Significant speed increases would just mean they'd catch up the stoppers, semifasts or freights in front on the two line sections though.

Both the XC services are currently pathed just behind the semi-fasts to/from Poole or Portsmouth Harbour between Southampton/Eastleigh and Basingstoke. They catch up with the semi fasts at Basingstoke northbound, ie 2 mins behind at Worting Jn.

IMHO you could only run the Weymouths and XCs at 110 mph if you raised the speed of all the SWT services on the fast or two track sections - and that's assuming any freight pathing can be resolved - and freight paths just keep increasing year on year...

 

[Eagle]

IMHO you could only run the Weymouths and XCs at 110 mph if you raised the speed of all the SWT services on the fast or two track sections - and that's assuming any freight pathing can be resolved - and freight paths just keep increasing year on year...

Ignoring freight, the trains that work south of Basingstoke (where the two-tracking starts) are 22xs, 444s and 450s; I can conceivably imagine that both the Desiros could be upgraded for 110 running (it's the rail itself that's more of an issue).

 

[LE Greys]

Ignoring freight, the trains that work south of Basingstoke (where the two-tracking starts) are 22xs, 444s and 450s; I can conceivably imagine that both the Desiros could be upgraded for 110 running (it's the rail itself that's more of an issue).

The fastest ever done along there was 108 with a 5-WES, so 110 is probably possible with a bit more traction or a better power-to-weight ratio. Thing is, I think they had to boost the line to 850V to get it to work. Of course, they really ought to quadruple the whole route, except for Winchester station perhaps, which would be tricky. Running the fast lines on the outside through Micheldever might help there, meaning that Winchester would be the crossover from outside to inside. I'd also go with 125 rather than 110 as the maximum, allowing Voyagers full speed, but they'd generally do 110 unless running late so that they could fit in with other traffic.

 

[HSTEd]

The question is, is the expense required in the piecemeal conversion of the existing third rail territory to 25kV overhead justified in a time when the MML, GWML and half a dozen other routes are all calling out for electrification?

 

[Mike C]

Would be intresting to see how these controllers have been specified for the newer units, 350 onwards (IGBT Based kit, rather than the GTO based SSCs)

Indeed. Our train is TGV Atlantique vintage (early '90s) and is GTO equipped. Whether IGBT's would fare better is difficult to say. You might find the limitations for either will be cooling or the integrity of contactors and other components.

 

[pendolino]

...perhaps this is something that NR should be monitoring to find the low voltage areas and do something about it by either improving or adding feeder stations???

They are though. Off the top of my head, a new TP hut went in at Gypsy Hill recently and the entire East Grinstead branch has had a substantial power upgrade with new feeders at Woldingham and Eden sub. The trouble is, there is still a fair amount of equipment, transformers, rectifiers etc. on the 3rd rail network that dates from the 50s (so I've been told) which is hugely expensive and hugely disruptive to replace.

 

[Nym]

Indeed. Our train is TGV Atlantique vintage (early '90s) and is GTO equipped. Whether IGBT's would fare better is difficult to say. You might find the limitations for either will be cooling or the integrity of contactors and other components.

Isn't just the semiconductors being used, but that the switching schemes and systems have gotten significantly more advanced, if I'm thinking right the 90s GTO systems where based on either a 120 or 180 deg quasisquarewave switching scheme with little regard for any PWM or harmonics, with todays more advanced controller setups, such as ABB's multi level cascade PWM switching systems that get damned close to true sine waves, one would think that for an application where voltage drops are likely that such systems would be designed to be able to work in lower voltage enviroments, especially with controlled rectifiers for grid feedback (actually setup like invertors, but run in 'rectifier mode') one can build in low voltage resitance into the switching scheme. The only current advantage a'la IGBT vice GTO of course is how much easyer they are to turn off...

They are though. Off the top of my head, a new TP hut went in at Gypsy Hill recently and the entire East Grinstead branch has had a substantial power upgrade with new feeders at Woldingham and Eden sub. The trouble is, there is still a fair amount of equipment, transformers, rectifiers etc. on the 3rd rail network that dates from the 50s (so I've been told) which is hugely expensive and hugely disruptive to replace.

Oh indeed, VERY expensive, and it isn't getting cheaper thanks to China at the moment, also thanks to the much stricter harmonics regulations meaning one can't simply put in a 12 pole rectifier and glue it to the conductor rail any more like we used to.