Question for Electrical Engineers

[Domeyhead]

HS2 is specifying new trains capable of 360kph (perhaps the reality will prove to be 320 kph but still pretty quick).
I am curious about the catenary behaviour at those speeds. I don't know what upward force the pantograph applies to the wire but I guess it must be fairly substantial to counter wind etc. but does that then cause high friction temperatures on the contact bar because it feels like it would get pretty damned hot at the point of contact. If that is a factor, would that then inhibit the amount of useful current passing across the contact? The trains will be using a colossal amount of power at that speed so any increase in resistance would be a major problem.
Any expert opinion welcome. Thanks.

 

[najaB]

I don't know what upward force the pantograph applies to the wire but I guess it must be fairly substantial to counter wind etc. but does that then cause high friction temperatures on the contact bar because it feels like it would get pretty damned hot at the point of contact.

I believe they use a graphite contact strip specifically because it is conductive *and* an extremely low friction surface.

 

[bangor-toad]

Hi there,
There's a whole load of clever science and engineering devoted to this issue. Google phrases such as "catenary contact strip" for lots of information and recent scientific publications.

Fundamentally the choice of materials is important. There's a lot more to it than just rubbing a copper bar along a copper wire. As najaB mentions there is now a lot of graphite used. It is conductive but as it wears away it self lubricates. There's a lot of research going on in how to bond copper and graphite giving optimal performance.

A simple "trick" to avoid one spot getting worn is in the design on of the overhead cable. A well designed intallation will gently vary the OHLE from left to right and back so that the point of contact between the wire and the pantograph moves from side to side.

There's a lot of clever people working on this and they seem to be doing some great work...
Cheers,
Mr Toad

 

[GRALISTAIR]

Hi there,
There's a whole load of clever science and engineering devoted to this issue.
Fundamentally the choice of materials is important.

One trick is to embed copper flake/powder in the graphite. This tends to improve the impact resistance.

 

[Tio Terry]

Have a look at the Energy Technical Standard for Interoperability. It has a lot of information about pantograph and contact wire specifications in it.

 

[John Webb]

........A simple "trick" to avoid one spot getting worn is in the design on of the overhead cable. A well designed intallation will gently vary the OHLE from left to right and back so that the point of contact between the wire and the pantograph moves from side to side......

All overhead lines where pantographs are in use have this feature - even tram lines running at around 750 volts as well as the main line 25,000 volt systems.

John Webb

 

[AM9]

All overhead lines where pantographs are in use have this feature - even tram lines running at around 750 volts as well as the main line 25,000 volt systems.

John Webb

Well just nit-picking, but only tramlines with bow or pantograph collection. Trolley poles don't need staggered conductors.