Electric Traction, re: ground circuit return?

Trains Magazine General Discussion
1

Last week, while chasing some ghosts of the Pacific Electric Railway through Bellflower, Calif., a technical thought crossed my mind. The issue applies to heavy electrics, interurbans, streetcars, and the like.

Recognizing that electric power flows from an overhead wire or third rail, through a variety of circuits, and back through the track to its source, how exactly does the power flow through the wheels to the track?

Grounding the circuits to the truck bolster or truck side frame strikes me as completely impractical because the electricity would have to flow into the journal box brass and through a thin film of oil before it would reach the machined end of the axle. The result would be a lot of arcing within each journal box and the high probablility of the cotton waste catching fire.

For rolling bearing equipped units, the issue would be just as serious because of the possible arcing and pitting among the ball bearings.

Lehmann Gross Bahn, manufacturers of G-scale model trains, uses a truck-mounted contact shoe that rubs along the top of the rail to complete the return circuit, but I’ve never seen any prototypes use such an arrangement.

Or, did the traction motor cases have something along the lines of a built-in exterior brush - one made out of brass or bronze filaments - that rubbed on the inside of the axle thus completing the circuit?

Whether the rolling stock was a two-axle Birney, an “el” rapid transit car, an Electroliner, GG1, or “Little Joe,” the issue is the same. How exactly did electricity reach the wheel-and-axle sets without damaging the wheel bearing

2

On trains they use ground brushes (carbon) that ride on axle either in middle or at end near bearing cap, they are a assembly housing riding on axle containing 3 really hard carbon brushes, even on non electrified rolling stock ground brushes are required for signal bonding, HEP ground or other electrical grounding.

3

And a question I’ve always had about this, too. Once the power gets to the track, the circuit has to be completed to the powerhouse. If I understand correctly, the earth itself is a common ground, yet the rails are bonded to allow current flow through them. So what happens at the powerhouse siding? A honkin’ huge cable to run the ground back to the generators? Talk about arcing problems there! If that’s not it, a big grounding rod buried beneath the building to ground to the earth? Or is the circuit completed at each substation or feed into the catenary/third rail? Or has no one thought about this yet and we’ve been pumping up the entire North American rail system like a giant capacitor for 100 years?

4

Each rail joint is bonded for electrical continuity , at the power house or substation there is in fact a big cable or a series of cables to return negative current to the converters. Loss of proper bonding has been responsible for many problems related to electrolysis and is a serious problem when discovered. Electricity will find a way back to the powerhouse using water pipes, gas mains, telephone conduits and other railroads especially if there is another electric railroad in the vicinity . In one example an electrolysis study was done in Milwaukee in the 30s and current was found wondering from the TMER&L track in Kenosha , over to the CNS&M tracks and returning to Milwaukee via the NSL , CNW and city water pipes. A broken bond can cause injury and electric railroads have rules in case a car loses it’s ground (neg), The procedure involves pulling the trolley pole and visually looking for the cause of the broken continuity, sometimes repaired by driving a spike between rail joints.

5

A casual inspection I made a few years ago of the Illinois Railway Museum tracks revealed heavy bond wires at each rail joint. They were on the order of what I’d expect to see along the Chicago, South Shore and South Bend or The Milwaukee Road west of Harlowton, Mont.

Nearly all of the rail joints I saw last year at the Fox Valley Trolley Museum in South Elgin, Ill. had much thinner bond wires, the kind one would expect to find along any non-electrified, yet block-signal-equipped mainline. But, only one rail was bonded. But then, Fox Valley doesn’t run nearly as many train sets at one time - nor move as much electric current - as the I.R.M.

I seem to recall too from a trip I made in April 1993 that Fort Smith, Ark. has a very short Birney (?) operation that didn’t have any bond wires at all. In wet soil these folks could be asking for trouble from spurious electrolysis because none of those joints were bonded. Perhaps that’s been rectified in the last 14-years.

6

Ohm Sweet Ohm!

7

Generally the length of the ground return is only a few miles to the closest transformer (RR or not). May be even less depending on if there is a neutral on the catenary poles. Remember, those electrons were “pumped out the ground” by the generator and are just replenishing an infinite supply.

dd

8

Remember , electricity always returns to it’s source, one way or another . In electric traction you do not want any of your potential on a neutral !!!

9

Especially if your body becomes part of the circuit [:D]

When I was up in Washington we had a contractor trenching in cable with a trenching machine. He hit a primary power line (7200 VAC) with the blade. He survived that, but while walking (more likely running) away from the machine he stepped in a place where he became part of the circuit and it killed him. Tragic loss.

10

Exactly , the neutrals are there to protect us. What happens if the ill maintained electric railroad down the street puts a 600 volt dc potential into your house ?

If a 20 mile electric railroad has one sub , at one end of the railroad the return path through the rails is also 20 miles

11

I deal with similar problems with coax communication lines (ground loops, ect.) but it is usually not dangerous, it does wreak havok with TV pictures though and are usually the harder problems to resolve. Good grounding in theory is the cure but what happens if you have a 500KV line cross your path (or a electric railroad) that can significantly alter ground voltage?[:O]

12

In the Swiss system there is a return cable on the cantenary supports and a cable from the track running to this return cable at every cantenary support. They don’t take chances.

13

Well, memories of growing up on the railroad, this is actually a talking parakeet story, but part of it is about getting in the circuit –

At Primrose substation, after the remote control equipment was
installed, the second operator house was sold off and moved off the
property. Typically, the powers that be then decided that they needed
housing for a relief operator to live at Primrose. I believe he was to
serve as relief for the operators at Primrose, Tarkio, and, I believe
Ravenna, although Ravenna was not part of the remote control group
served by Primrose.

A mobile home was brought in, and we kids always used to like to visit
Charley and Kay. I no longer remember their last name. But Charley was
the relief operator. We liked to visit particularly when Charley was
just about to come off of his shift when he had day shifts. He would
come walking around the west corner of the substation, and come into
view of the front window of the mobile home, which was placed by the
company pumphouse.

Charley and Kay were the owners of a parakeet that we kids were
convinced was the brightest bird in the world. His cage was near the
front window and, when he would see Charley come round the corner of the substation coming home, the bird would urgently announce: “Dammit, here comes Charley!”

Now, at the time, we were too young to appreciate where the bird had
probably picked up this phrase, or why. We thought it was his own doing,
and we were particularly impressed by the philosophical strength of the
expression that the bird was able to convey by the use of the
declarative, “dammit.”

Invariably, Charley would come in the door just as we were picking
ourselves up off the floor after spasms of pre-adolescent
semi-hysterical laughter at the bird’s announcement. We weren’t allowed
to say things like “dammit,” of course, but this bi

14

That’s a good one Michael. Concerning neutrals, several years ago the neutral on mine house service went bad. The service was therefore trying to depend on the ground for the return path to balance the voltages and because of this the voltages in the house were very unbalanced. This is not good for lights, tvs, refrigerators, etc!

15

It is also a good way to get hurt in a hurry. If you lose the neutral connection on any electrical service, the juice will find an alternate path to the earth. (The earth is usually a default conductor for electricity). Since most electrical services are bonded to water pipes by code, the plumbing becomes the stand in neutral. All fine and dandy until the plumber removes the water pipes because the increased galvanic action rots out the pipes. Suddenly he can become the neutral. Not good either way you slice it.

Another tidbit - more electricians get killed because they don’t understand how a neutral works. They think it is dead, when in fact it isn’t. Neutrals can be very dangerous. Not so bad in a house, but on a 35 KV primary line breaking the neutral can be disasterous!!

16

I agree, Throw in the concept of phase and forget about it.[banghead]

17

[quote user=“MichaelSol”]

Well, memories of growing up on the railroad, this is actually a talking parakeet story, but part of it is about getting in the circuit –

At Primrose substation, after the remote control equipment was
installed, the second operator house was sold off and moved off the
property. Typically, the powers that be then decided that they needed
housing for a relief operator to live at Primrose. I believe he was to
serve as relief for the operators at Primrose, Tarkio, and, I believe
Ravenna, although Ravenna was not part of the remote control group
served by Primrose.

A mobile home was brought in, and we kids always used to like to visit
Charley and Kay. I no longer remember their last name. But Charley was
the relief operator. We liked to visit particularly when Charley was
just about to come off of his shift when he had day shifts. He would
come walking around the west corner of the substation, and come into
view of the front window of the mobile home, which was placed by the
company pumphouse.

Charley and Kay were the owners of a parakeet that we kids were
convinced was the brightest bird in the world. His cage was near the
front window and, when he would see Charley come round the corner of the substation coming home, the bird would urgently announce: “Dammit, here comes Charley!”

Now, at the time, we were too young to appreciate where the bird had
probably picked up this phrase, or why. We thought it was his own doing,
and we were particularly impressed by the philosophical strength of the
expression that the bird was able to convey by the use of the
declarative, “dammit.”

Invariably, Charley would come in the door just as we were picking
ourselves up off the floor after spasms of pre-adolescent
semi-hysterical laughter at the bird’s announcement. We weren’t allowed
to say things like "dammit,&qu