Italian OLE

[nlogax]

I've been spending the last few days in Milan. All the way from Centrale and its considerable approaches to at least as far as Monza (where I've been travelling every day) on every line I could make out I've noticed that the overhead equipment features double contact wires. They're not a secondary catenaries..there are definite droppers and registration arms for both.

Example here (not my pic); http://i4.ytimg.com/vi/ufFN_wOfrUo/maxresdefault.jpg

Any particular reason for this?

 

[MisterT]

You'll see this on many of the 1,5 and 3 kV DC networks. We do the same in the Netherlands.
We do it to prevent the wires from overheating and melting by basically extending the contact area between the pantograph and the wires.
Another way to prevent the wires from breaking down is to use both or two pantographs (in case of a loco hauled train) while at a station stop.

 

[J-2739]

It's to carry a three phase current- multi-overhead wire used to be common in Italy but problems with short circuits led to their demise.

 

[endecotp]

It's to carry a three phase current

No! Much too close together, and the pantograph shorts them together.

 

[MarcVD]

3 phase current on italian Railways disappeared decades ago.

On all 1500 and 3000 V Railways the contact wire is doubled to be able to carry the current. 3kV locs can draw easily 4000 amps when they start.

But what you see on this picture is just the junction between two successive sections of wire. The wire is cut in sections and not just joined together so that it can be maintained under constant mechanical tension by weights.

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[nlogax]

Thanks all. I'm now trying to figure out which lines heading north from Centrale are 'conventional' lines with DC and which are AC. From initial perspectives, the approaches are vast and pretty confusing.

But what you see on this picture is just the junction between two successive sections of wire. The wire is cut in sections and not just joined together so that it can be maintained under constant mechanical tension by weights.

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Yes, I realised I may have found a transitional section photo which doesn't best demonstrate what I saw. This is a better example; https://sestonews.files.wordpress.com/2012/03/fs-sesto_san_giovanni-021.jpg

 

[MarcVD]

Ok that last picture is just the double contact wire as I explained earlier.

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--- old post above --- --- new post below ---
AFAIK the only lines with 25 kV in Italy are the récent HSLs and everything else is 3 kV. The 3kV catenary design also looks older notably vith the suspension wire going above the consoles and not below like you can see on your last picture. Only FS and NS are doing this...

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[Gordon]

Another way to prevent the wires from breaking down is to use both or two pantographs (in case of a loco hauled train) while at a station stop.

This why on French DC lines you will see locos with both pantographs up as they depart with a heavy train - as soon as the loco is moving the second panto drops gracefully as the train moves away.





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[axlecounter]

I'll just add that in some lines they even started using three wires instead of "just" two!

 

[AM9]

Ok that last picture is just the double contact wire as I explained earlier.

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--- old post above --- --- new post below ---
AFAIK the only lines with 25 kV in Italy are the récent HSLs and everything else is 3 kV. The 3kV catenary design also looks older notably vith the suspension wire going above the consoles and not below like you can see on your last picture. Only FS and NS are doing this...

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Also, the (older) 3KVDC OLE has a heavier appearance with more droppers to distribute the heavier load better onto the catenary wire. The other major difference is the insulator sizes. Lower voltage insulators are shorter with fewer 'discs', sometimes as few as two whereas 25kV versions look more like the national grid types, (because of the higher voltages). See the pictures below:






I couldn't find a picture of an Italian Pendolino showing 25kV OLE, so here is a more local one, (at least it is a Pendolino!)

 

[Flying_Turtle]

I've been spending the last few days in Milan. All the way from Centrale and its considerable approaches to at least as far as Monza (where I've been travelling every day) on every line I could make out I've noticed that the overhead equipment features double contact wires. They're not a secondary catenaries..there are definite droppers and registration arms for both.

Example here (not my pic); http://i4.ytimg.com/vi/ufFN_wOfrUo/maxresdefault.jpg

Any particular reason for this?

Very short answer:
Lower voltage; same trains; bigger amperage

 

[contrex]

I have seen double 1500 V contact wires in France, and if I remember correctly, at Dunford Bridge on the Woodhead scheme. I have a French video from Rail Passion where a DC loco was taking a heavy freight out of a siding at dusk. The track seemed to be a bit uneven because the loco was visibly rocking from side to side causing much arcing at the panto. Straight after the more spectacular arcs you could see the two contact wires adjacent to the panto glowing orange-red and fading over about half a second. I expect it would need replacement more often. I also saw a clip of a 1955 record run with either CC 7107 or BB 9004 where 331 kph (206 mph) was achieved on the Bordeaux - Dax line. There was much arcing there and I believe a lot of the track and OHLE was unusable afterwards and needed putting right before the line could be reopened for traffic. I think the supply was considerably beefed up, with extra temporary substations, jacked up voltage etc.

https://www.youtube.com/watch?v=cHWjelxe_MU

 

[MarcVD]

In Belgium (3 kV =) train drivers must raise the 2nd panto if starting their train from à track which is not equipped with 2 contact wires.

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