Catenary/pantograph question

[David_Telesha]

no, you're dealing with an electric motor and a train thats a few dozen tons at least.

[Kevin C. Smith]

QUOTE: Originally posted by daveklepper

Note that there were a variety of voltages and power used in electrification. Today, a Washington to Boston train starts out using the original 11,000 volt 25-cycle ac electrification, switches to 60-cycle, 25,000 volts just beyond Harold Tower, Sunnyside, on the Hell Gate Bridge approach, then to 12,500 volts to enter Metro North tracks at New Rochelle, keeping 60 cycles per second ("Hz"), then back to 25,000 volts when east of New Haven station and keeps that on the new electrification up to Boston.

And a Metro North commuter train uses 60Hz power from New Haven to Mount Vernon, then coasts while dropping pantographs and having its third rail shoes pick up 650volts dc on the third rail into Gramd Central Terminal.

And Metra Electric and the South Shore both use 1500 volt DC on overhead catenary.

Most new light rail systems use 750 volts DC on catenary and older systems, including new extensions, 600 volts DC on simple trolley wire.

The Milwaukee used 3000 volts DC in its catenary except when on tracks shared with the Butt Anaconda and Pacific where the voltage dropped to 2200 volts.

And the new standard in Europe is 50 Hz AC because that is the standard power frequency there, but there are plenty of 16-2/3 Hz electrications and plenty of 1500 volt DC, 750 volt DC, 3000 volt DC and 600 and 550 volt DC electrifications around.

I know the PRR reduced the voltage in the Hudson River tunnels when they strung overhead wires, due to limited clearance. Which got me wondering-what are the minimum clearances (above equipment) for the most common electrification voltages-1,500/11,000/25,000 volts? Does AC or DC make any difference? I've heard many times that a major cost of electrification is raising overhead structures, so I know you just can't staple a 25kv line to the underside of a bridge. (You think the thread about trains stopping on a bridge with no walkways was funny until the typo got fixed; I just did it here, too!-but caught it in time. Still, it read hilarious!)

[Anonymous]

I believe the Southern Railway (this side of the Atlantic) built a series of three 3rd-rail electric locos with large flywheels (numbered CC1-CC3, later Class 70) fitted in order to deal with breaks in the conductor rail. There was also some overhead wiring fitted in yards to avoid the risk to crews of 3rd rail - tram-type overhead was used to keep costs down as at yard speeds it functioned perfectly well, and the later Class 71 was also fitted to work from this overhead along with 3rd rail.

Link to Class 70 page : http://en.wikipedia.org/wiki/British_Rail_Class_70

Link to Class 71 page: http://en.wikipedia.org/wiki/British_Rail_Class_71

[Dutchrailnut]

clearances to ground for 1500 volt is about 4"
for 11.5Kv is about one foot
for 25Kv is two foot

These clearances are to be doubled since you need clearance between structure and wire, plus between wire and train.

[CSSHEGEWISCH]

The Chicago, Aurora & Elgin, which was primarily a third-rail operation, had a stretch of trolley wire strung over an especially long grade crossing which included a regular station stop near the roadway. Coasting across the grade crossing could be difficult when attempting to accelerate away from the station so the wire was in place to prevent stalls in the dead zone.

NYC installed overhead third rail, not catenary, in GCT and in parts of its Detroit River electrification to cover the gaps, especially around double slip switches.

[dldance]

Many of the pictures posted at the following web site show Swiss electrical overhead from the engineers view. The camera is in the cab of a Swiss engine and posts a picture to the internet about once every 15 minutes.

dd

http://home.rol3.com/myswitzerland/Livebild.jpg

[wallyworld]

I used to live next to the Chicago North Shore and Milwaukee station in Mundelein. This was a electric interurban with both catenary and direct hung contact wire at 600 volts DC. They would install "sleet cutters" on some Merchandise Dispatch cars and run them to clear ice from the overhead. The road also ran on 3rd rail and sleet cutters were used on the 3rd rail as well. Some interurban cars had a control to the right of the brake on the control stand to put a 3rd rail sleet cutter into action. The arcing could be pretty spectacular on the overhead especially at cross-overs where the pole had to be pulled down and set back on the wire while the cars where in motion by a conductor hanging out the rear door pulling on the retriever rope. I was always amazed they did this at night as well or in other bad weather like blizzards, heavy rain etc and managed to hit the wire every time I watched them. And then...flash! It was interesting to watch.

[Isambard]

QUOTE: Originally posted by jchnhtfd

One might also mention -- in connection with gaps -- that a number of the NYC motors which worked Grand Central had tiny (and I do mean tiny -- so small they looked really silly!) pantographs on each end, and at some really complicated switchwork there were short sections of catenary in place of the third rail, to keep things moving. Otherwise, you just coast through the dead section.

Of course, if you stop... the dispatcher tends to get a bit fractious.

Aha, the mystery that has bothered me since was a kid is now explained. I had inherited my uncle's mid 1930's Lionel train, which was headed by an NYC electric loco in orange, with a cab in the centre, and those tiny pantographs, which indeed looked silly to me, since I was a fan of the Great Northern and Milwaukee Road electrics with their impressive pantographs.

[:)]

.

[Isambard]

QUOTE: Originally posted by jchnhtfd

One might also mention -- in connection with gaps -- that a number of the NYC motors which worked Grand Central had tiny (and I do mean tiny -- so small they looked really silly!) pantographs on each end, and at some really complicated switchwork there were short sections of catenary in place of the third rail, to keep things moving. Otherwise, you just coast through the dead section.

Of course, if you stop... the dispatcher tends to get a bit fractious.

Aha, the mystery that has bothered me since was a kid is now explained. I had inherited my uncle's mid 1930's Lionel train, which was headed by an NYC electric loco in orange, with a cab in the centre, and those tiny pantographs, which indeed looked silly to me, since I was a fan of the Great Northern and Milwaukee Road electrics with their impressive pantographs.

[:)]

.

[Murphy Siding]

Some have mentioned sparks, flashes, and such. Were/are those type things common with overhead catenary? Things like that would scare the bejeebers out of me.

[David_Telesha]

Its arcing. Happens when the pan bounces or temporarily looses/re-makes contact.

[beaulieu]

QUOTE: Originally posted by Murphy Siding

Some have mentioned sparks, flashes, and such. Were/are those type things common with overhead catenary? Things like that would scare the bejeebers out of me.

Happens fairly often at speed. Kind of neat to watch at night.

[kenneo]

QUOTE: Originally posted by beaulieu

QUOTE: Originally posted by Murphy Siding

Some have mentioned sparks, flashes, and such. Were/are those type things common with overhead catenary? Things like that would scare the bejeebers out of me.

Happens fairly often at speed. Kind of neat to watch at night.

Steam = smoke signals

Electric = Arc signals (aka "hot flashes" when unit is over age 50)

[trainboyH16-44]

QUOTE: Originally posted by Murphy Siding

Some have mentioned sparks, flashes, and such. Were/are those type things common with overhead catenary? Things like that would scare the bejeebers out of me.

It's not as scary as you might think, and it's incredibly common, even with new LRTs. When I take it to school in the morning, there's this weird section in a tunnel where blue flashes light it up, and it's pretty neat to watch!

[jchnhtfd]

The arcing is almost inevitable at any kind of speed at all, as the pantograph is held against the wire by springs, and both the pan and the wire can move -- and lose contact now and then. Sometimes on very high speed service (and also, due to the peculiarities of the machinery, on some of the old Milwaukee motors) both pantographs are used at once, to minimize the problem.

[BR60103]

Can anyone confirm that at switches one contact wire would run above the other? Not sure how that affected the Pantograph contact. I'm sure at high-speed turnouts they tried to run the wires parallel for a section.
The Edmonton trolley line had an interesting bit of overhead. The line came to the surface and crossed a trolley bus line at grade. Fortunately the crossing was an acute angle. There was a little bit where the trolley line was bent to parallel the trolley bus wire and a stretched Z shaped piece in between so that the pan didn't lose power. I suspect the trolley bus wire was a bit higher than the trolley so that they didn't short to the return wire.

[daveklepper]

There are special trolley wire frogs that join or have cross to trolley wires while keeping them both on the same level, with grooves for the sides of a trolleywheel or trolleyshoe as used on trolleypole streetcars and itnerurban cars and locomotives, including the North Shore when it was running. Panatographs have no trouble with these when properlly designed, but a more usual practice is simply to parallel the two wires for a few feet, while the pantograph is contacting both wires. Special insulated trolley frogs are used for crossings of trolleybus and rail lines or two trolleybus lines where the frog in the air is an insulated "dead" zone.

I was not aware of any reduction in the 11,000V 25Hz AC PRR tunnels either in NY or in Baltimore (equally restrictive). Perhaps that is becauses improved insulation materials made the voltage reduction unnecessary at a certain time.

[ndbprr]

Trolly contact is different than high speed trains. Generally a trolley either uses a wheel or a contact shoe with a frog for lack of a better description. The car movement and pole tend to pull the shoe or wheel in the correct direction. On high speed corridor trains the contact wire has a second wire clipped to the first in the same manner the contact wire is supported. If you look closely at a high level platform you will see that a clip grips the upper half of the wire and has a nut and bolt to squeeze and hold the contact wire. It is a fairly simple procedure to just have a short length of catenary to connect tracks through turnouts. Arcing also occurs in wet weather when the shoe hydroplanes from the water hanging on the wire.

[Murphy Siding]

QUOTE: Originally posted by trainboyH16-44

QUOTE: Originally posted by Murphy Siding

Some have mentioned sparks, flashes, and such. Were/are those type things common with overhead catenary? Things like that would scare the bejeebers out of me.

It's not as scary as you might think, and it's incredibly common, even with new LRTs. When I take it to school in the morning, there's this weird section in a tunnel where blue flashes light it up, and it's pretty neat to watch!

I realize these are *dumb* questions, but i am perhaps 1,000 miles away from an electric train line........Are the flashes accompanied by sound? I'm imagineing a big *BZZZZ* like a bug zapper(?) Truely, I have no idea what it is like). Thanks

[BR60103]

Murphy: the sound is a sharp "pop". It's the sound you get when you unplug a kettle, but bigger,
The Toronto subway produces flashes when the shoes beak contact with the 3rd rail at switches, a nice big blue flash. There was an article in a British mag about sumulkating the flash -- I think they used a photo flash unit.

[Kevin C. Smith]

QUOTE: Originally posted by daveklepper

.

I was not aware of any reduction in the 11,000V 25Hz AC PRR tunnels either in NY or in Baltimore (equally restrictive). Perhaps that is becauses improved insulation materials made the voltage reduction unnecessary at a certain time.

OR-and this is far more likely-I am entirely mistaken.

[daveklepper]

Sometimes a flash is acompanied by a sputtering kind of sound, and this can happen both with third rail and with trolley wire.

[BrianLM007]

You also get a "twang" sound when the pantograph makes contact with the catenary, particularly if there are multiple pantographs. You see this on the NICTD platforms at the Randolph St. Station when the South Shore engineers will switch the pantograph positions (he/she will first lower all the pantographs, of which there can be up to 8, than after about thirty seconds, he/she will raise the opposite pantographs) in preparation for departure back to Indiana.

You can get quite a little show while you wait to board!

BrianLM007
A South Shore Regular

[Murphy Siding]

QUOTE: Originally posted by BrianLM007

You also get a "twang" sound when the pantograph makes contact with the catenary, particularly if there are multiple pantographs. You see this on the NICTD platforms at the Randolph St. Station when the South Shore engineers will switch the pantograph positions (he/she will first lower all the pantographs, of which there can be up to 8, than after about thirty seconds, he/she will raise the opposite pantographs) in preparation for departure back to Indiana.

You can get quite a little show while you wait to board!

BrianLM007
A South Shore Regular

I'm really unfamiliar with this. Does the South Shore have MU cars, so that each one has an individual pantograph? Is there a pantograph at each end of the car,for example, one for going north, one for going south?? Can you expand on that please? Thanks

[daveklepper]

Most mu's and electric locos have two pantographs, assuming they are bidirectional and almost all are. Generally each pan. is located over a truck center to insure alignment with the overhead wire. The rear pantograph is the one normally used. The theory is that if there is trouble, the front pantograph in store position has alreay passed the bad spot and can be used to continue operation.

Other than special trains hauled by locomtives, the South Shore has always used self-propelled electric cars, single cars for the very first few years and then and now mu cars. There are a few non-powered trailers without pantographs.

[Kevin C. Smith]

QUOTE: Originally posted by Dutchrailnut

clearances to ground for 1500 volt is about 4"
for 11.5Kv is about one foot
for 25Kv is two foot

These clearances are to be doubled since you need clearance between structure and wire, plus between wire and train.

Wow-WAY less than I'd have thought. How come the clearances in practice are so much more? It seems to me a GG1 pantograph would rise to about 3-4 feet to make contact. Or am I (again) grossly mis-estimating?

[CSSHEGEWISCH]

South Shore's MU cars, both from the Insull era and the present versions, have always had two pantographs. South Shore's operating rules state that the trailing pantograph is to be raised unless circumstances demand otherwise.
The Insull era trailers (12 coaches, 2 eight-wheel parlors later converted to coaches, 2 twelve-wheel parlors and 2 twelve-wheel diners) never had pantographs, but the coaches did have control cabs. The current trailers do have pantographs for heat and light but do not have control cabs or end windows.

[BrianLM007]

Looks like CSSHEGEWISCH and daveklepper answered pretty well for me, but I will also add this: there are 68 cars in the fleet. The breakdown is as follows:

Cars 1-48: MUs, 2 Pantographs at each end, 2 cabs (one at each end).

Cars 101-110, MUs, 2 Pantographs at each end, 1 cab (If the car is on a North-South track, cars 102, 104, 106, 108 and 110 have a cab at the North end, and cars 101, 103, 105, 107, 109 have their cabs at the South end).

Cars 201-210, Trailers, 1 Pantograph (If the car is on a North-South track, the pantograph is on the South end of the car).

A typical 8 car consist often looks like this:

MU - MU - Trailer - MU - MU - Trailer - MU - MU

You normally see 8 pantographs raised while in operation. When it is very cold, however, you will often see both pantographs raised on the first car (so there are 9 pantographs up during those times).

To give you an idea of what you are looking at, here are a couple of links of South Shore Cars:

NICTD Car #1 (From the Nippon-Sharyo (manufacturer's) website):

http://www.n-sharyo.co.jp/business/tetsudo/pages/zchicago.htm

A WB train from South Bend (From Thomas Kepshire's website):

http://www.monon.monon.org/railpixs4/07-18westbound2.jpg

Hope that helps.

BrianLM007

[Murphy Siding]

BrianLM007: Thanks for the links. I understand what you're saying now. Any explanation about why the trailing pantograph would normally be used-what difference would it make? Thanks

[Anonymous]

All the information here is great- thanks everyone! Electric locomotives seem to have "shoes" (for lack of a better word) on top of their pantographs while trolley cars have, well, trolleys- flanged wheels at the top of the pole.

A couple of questions- First, would not the pantograph "shoes" cause some kind of wear on overhead wiring, particularly with a train at high speed? I know that some interurbans were capable of fairly high speed, and they seemed to have poles with trolleys. Did the railroads experiment with a roller type arrangement on the pantograph? Wouldn't that reduce wear on the wiring? Seems to me that a shoe in contact with wire moving at 80 plus MPH would cause a lot of friction and heat....

Thanks,
Erik