Catenary/pantograph question

[MichaelSol]

QUOTE: Originally posted by Hugh Jampton
In France they melt ice from the contact wire by nearly shorting it out (a low resistance shunt is used) which causes the contact wire to heat up a bit.

On Milwaukee Road, which had more than its share of mountain ranges and weather conditions, if there was ice on the contact wire, both pans were run up, the first pan broke the ice, the second got good contact. Substation operators could also lower voltage and the higher amperage would heat the contact wire.

Also, the bottom of the contact wire was highly polished from the graphite grease worked into the wire over the years from the pantograph shoes. Kind of like Teflon. You would never see an icicle, for instance, hanging from the contact wire although you might from the steel messenger cable.

This is one of those "theoretical" problems that was not a problem in actual practice.

Best regards, Michael Sol

[Dutchrailnut]

The Pantographs are raised by spring tension. and lowered and locked by air pressure.

[ndbprr]

If you are not from the east coast you have no idea how sloppy the snow and ice are in PRR electrifed territory. Slush is a better description. A standing order was that all trains have both pantographs up during sloppy weather to help keep the catenary free of ice build up. Don;t forget that the PRR ran trains four tracks wide with about ten minutes between trains on all four tracks so build up would be minimal. It was also the job of the fireman to get out at every stop and check the pantograph shoes for arc through. The back pantograph was used in dry weather in case it got fouled and ripped off which did happen in which case the front one could the fini***he trip. Originally the PRR used carbon shoes on the pantographs but in the early 50's switched to steel shoes because of wear and cost. The catenary is not centered over the track but zig zags to even out the wear on the shoe and prevent grooving. The GN engines the PRR purchased were the only engine that required both pantographs be used in operation. This is because they were motor generators in which the AC from the catenary turned a motor that turned a generator to produce DC for the traction motors. In order that the motor not get out of phase with the power the pantograph had to be in contact with the wire 100% of the time. Sometimes they do bounce off the wire so two were the order of the day alsways.

[Anonymous]

I know that old fashioned trolley cars used springs on the roof to hold up the trolley pole. Do electric locomotives use the same kind of system? Also, how are the pantographs raised, or lowered? Once they lose their power, is there some kind of on board battery or something to provide power?

Erik

[Hugh Jampton]

QUOTE: Originally posted by Murphy Siding

QUOTE: Originally posted by dldance

QUOTE: Originally posted by Murphy Siding

So, the overhead wire is basically a "live" wire, hanging above the track with some sort of insulating material on the sides and top?

no insulation at all on the cat wire. The cat will be supported by insulators in the support arms or wires.
dd

What keeps ice and snow from interfering with the floe of electricity? For example, would a major ice storm short circuit the overhead juice?

This can happen,, as can the weight of the ice bringing the catenery down. Luckily the contact wire is not a superconductor, so the current flowing in the contact wire heats it up a bit which may melt ice. Snow is not usually a problem as it's light and shakes off due to the vibration of the wire.
In France they melt ice from the contact wire by nearly shorting it out (a low resistance shunt is used) which causes the contact wire to heat up a bit.

[CSSHEGEWISCH]

Ice storms have long played havoc with electrified operations, both overhead and third rail. Ice coating the wire or third rail actually serves as an insulator of sorts and limits current flow. Sleet cutters and ice breakers (not USCGC Mackinaw) are required to deal with this problem.

At any rate, the arcing that results when pantographs break off the ice coating puts on a pretty impressive light show.

[Murphy Siding]

QUOTE: Originally posted by dldance

QUOTE: Originally posted by Murphy Siding

So, the overhead wire is basically a "live" wire, hanging above the track with some sort of insulating material on the sides and top?

no insulation at all on the cat wire. The cat will be supported by insulators in the support arms or wires.
dd

What keeps ice and snow from interfering with the floe of electricity? For example, would a major ice storm short circuit the overhead juice?

[dldance]

QUOTE: Originally posted by Murphy Siding

So, the overhead wire is basically a "live" wire, hanging above the track with some sort of insulating material on the sides and top?

no insulation at all on the cat wire. The cat will be supported by insulators in the support arms or wires.

dd

[Murphy Siding]

So, the overhead wire is basically a "live" wire, hanging above the track with some sort of insulating material on the sides and top?

[Randy Stahl]

QUOTE: Originally posted by adrianspeeder

The power through the pantograph doesn't go straight to the motors. It is a "high" voltage "low" current power so that the catenary and pantographs don't carry obsurdly high currents.

Adrianspeeder

The current is pretty much as high as any locomotive (cept steam)... Current gets the work done !!

[Hugh Jampton]

QUOTE: Originally posted by cornmaze

What is interesting to me is that the pantograph frame itself (the tubing) is what carries all the current from the trolley wire to the motors. I guess if you're up there on top of the locomotive, you definitely do not want to touch that pantograph tubing, else the current will go right through your shoes to the locomotive roof which is 0 potential, being electrically connected to the rails.

Nobody goes on top until the pan has been lowered and the current wire switched and locked off. Even if you're not near the pan that current wire is still there just above your head.

[adrianspeeder]

The power through the pantograph doesn't go straight to the motors. It is a "high" voltage "low" current power so that the catenary and pantographs don't carry obsurdly high currents.

Adrianspeeder

[Anonymous]

What is interesting to me is that the pantograph frame itself (the tubing) is what carries all the current from the trolley wire to the motors. I guess if you're up there on top of the locomotive, you definitely do not want to touch that pantograph tubing, else the current will go right through your shoes to the locomotive roof which is 0 potential, being electrically connected to the rails.

[Hugh Jampton]

On most electrified systems ( overhead and 3rd rail) the electricity goes into the loco through the pantograph or contact shoe and it comes out of the wheels into the rails which are used as the return.

On 4 rail systems the electricity goes into the tain through a contact shoe on one power rail and out another contact shoe into a negative power rail.

[Randy Stahl]

Wire = pos
Rail= Neg
Some railroads had 2 trolley poles, 1 for positive, 1 for negative and some even used the rail for a 3rd phase leg

[Murphy Siding]

I've read a lot about electrified lines on, among others,PRR,NH,GN,NP, Milwaukee Road, Virginian,CN, and other roads. What I've never beem quite able to figure out, is how does the electric locomotive actually "plug in" to the power grid? Do the overhead lines carry both "wires", or is one above, one at the rail? Can anyone elaborate please? Thanks