LIRACOS for higher voltages?

[HSTEd]

Well I was looking at the Furrer and Frey website and discovered LIRACOS.
This is a light rail catenary system that is heavily simplified and apparently uses composite cantilever arms to reduce the component count and weight neccesary for insulation purposes. (the cantilevers are partially made of composite "rope" instead of rigid tubes).

This system is apparently rated for DC voltages up to 4kV but the length of the composite pole seems to be longer than that.
As this system is likely quite a lot cheaper to acquire than conventional systems on lower top speed routes, is there any particular reason that it could not handle 25kV without major difficulties (the increased power demands of heavy rail vehicles would not be an issue as it is designed for 150mm^2 contact wires which would be easily sufficient at 25kV)?

Or is this simply a lack of demand for such systems.

 

[WatcherZero]

Theres some 3kv DC systems around the world, mainly Belgium and Russia but also legacy systems in a few others, mostly being phased out though because A: Not as efficent as 25kv AC, more energy lost through higher electrical resistance and B: 25kv AC has become the standard for universal running.

What does seem to be happening is where practical 25kv Auto transformer is becoming standard, cheaper, lighter and twice the distance between transformers.

Licaros also has a maximum speed of 50mph.

 

[HSTEd]

Theres some 3kv DC systems around the world, mainly Belgium and Russia but also legacy systems in a few others, mostly being phased out though because A: Not as efficent as 25kv AC, more energy lost through higher electrical resistance and B: 25kv AC has become the standard for universal running.

What does seem to be happening is where practical 25kv Auto transformer is becoming standard, cheaper and twice the distance between transformers.

Yes, I know this, I was asking if there was any technical reason why the LIRACOS catenary system cannot be made for 25kV or if it was simply the lack of demand for 25kV light duty equipment such as the niche it would fill.

 

[WatcherZero]

Its built for trams and light rail, only supports speeds up to 50mph, in the UK 75mph is really the slowest conventional speed with 90 and 100mph desirable for non-mainline use if possible.

Its funny we dont really think of our 125mph lines as high speed but a lot of other countries do and have much slower lines.

 

[HSTEd]

Its built for trams and light rail, only supports speeds up to 50mph, in the UK 75mph is really the slowest conventional speed with 90 and 100mph desirable for non-mainline use if possible.

Its funny we dont really think of our 125mph lines as high speed but a lot of other countries do and have much slower lines.

Yes, I was considering it for a scenario someone abroad asked me about wheree there would be large amounts of railway where 50mph is considered quite fast.

Also for 25kV light rail projects where 50mph would be the top speed for large parts of the route.

 

[WatcherZero]

Light rail vehicles can hit 50mph even when the stops are less than a km apart, cant imagine any conversion programs where the speed limit wouldnt be a limiting factor.

 

[HSTEd]

Light rail vehicles can hit 50mph even when the stops are less than a km apart, cant imagine any conversion programs where the speed limit wouldnt be a limiting factor.

Well for instance I was pondering the Conversion of the Tyne and Wear Metro to 25kV or the construction of any further Metro-style projects using 25kV Light rail vehicles for the sake of simplifying the power arrangements (one feeding point for the entire line and all that) and allowing for easier implementation of future through running onto heavy rail lines.

Also I was asked by an American pal what the cheapest way to electrify railways with speed limits in the 30-50mph range would be infrastructure wise.

 

[jopsuk]

What's the limit on Cornish and Devonian branches such as Looe? If the line to Penzance ever gets wired up (I appreciate how unlikely this is) it could be a cheap way of doing those whilst retaining them as "heavy rail" operations?

 

[Nym]

Yes, theres big reasons, without looking into it properly, provide a link and I'll have a glance over it for you...

AC Systems behave VERY differently to DC systems.

These 'rope' things in a DC system will be seen as a very large resistor, but the chances are they are formed of some kind of dielectric, that once you put in an AC system ceases to actually be a resistor and turns into something that will quite happily conduct the current from the OHL into the supports. Just looked at a photo, and it looks as if it uses insulating blocks, wouldn't work for 3kV AC, let alone 25kV

 

[ole man]

The Midland Metro has a system that used parafel ropes as cantilevers, these are made from kevlar, and can support 26mm tube.
They are held up by karabiner's which are stressed tested.
Have a look at Brecknall Willis website they also design and install light OHLE systems.

 

[HSTEd]

Yes, theres big reasons, without looking into it properly, provide a link and I'll have a glance over it for you...

AC Systems behave VERY differently to DC systems.

These 'rope' things in a DC system will be seen as a very large resistor, but the chances are they are formed of some kind of dielectric, that once you put in an AC system ceases to actually be a resistor and turns into something that will quite happily conduct the current from the OHL into the supports. Just looked at a photo, and it looks as if it uses insulating blocks, wouldn't work for 3kV AC, let alone 25kV

As far as I can tell the cantilevers struts are made from fibreglass (it says so in the catalogue I found). Even if you must use its bulk resistivity instead of its dielectric strength the figures it has are absolutely enormous, and would suggest that it could cope with such voltages anyway.

Do things like the Aramid cables apparently used in the design really conduct AC currents because that would seem a little ridiculous?

Link

Ofcourse this doesn't matter if you were to make the support posts out of utility poles or something.....

On a peripherally related note, I note that the 25kV supply at Grantham station passes under the footbridge with no ceramic insulator, as I have not seen any neutral section boards or the like in the station and I do believe having one inside the station would present operational difficulties I must assume that the arm attached to the bridge is made of something insulating and that it does indeed work.