In most cases the rail return on an electric railway or street railway are not intentionally grounded. This was done to protect underground utilities from electrolysis damage. In a modern system there are ground relays that grounds the rails at the substations if the difference between the earth ground and the rail return gets too high. There were a few systems that did not use the rails as the power return allowing the rails to be used as a safety ground. The two conduit systems, NYC and Washington DC, were this way and, I beleive, two systems that used two trolley wires, maybe Cincinnati and Tacoma.

In a typical transit system today there is a power return wire and a safety ground wire. There are connected to two different ground brushes that wipe on the same axle. I have seen a subway car accelerating away from a station momentarily contact the fence at the end of the platform, which was tied to earth ground, and produce a shower of sparks. I have also thrown track switches and had arcs between the points and the stock rail. On the North East corder there was an IEEE paper addressing this issue where they measured over 1000 volts between the catenary pole ground wires and the running rail when a train was passing at high speed The one that really scares the safety people are trolley coaches.

The National Electric Code normally does not cover industrial plants and railways. When you go to the utility for service they ask for the design drawings, stamped by a registered electrical engineer. No permit or inspection is required. Recently an electric railway museum was going to build a new converter station at a remote location. They sent a letter to the county building department advising them that the building was going to be built and the AC to DC conversion equipment installed. The letter also said that this was a courtesy notice as the county had no authority over a railroad converter station. The local utility was provided with properly engineer drawings. There was no problem from either the county building department or the utility. The converter station was built, connected to the utility 12000 volt system, and is providing DC power to the museum's trolley line.

Rock Island Lines is correct. Contemporary light rail and metrorail systems are designed and built with the rails insulated from ground. This is to deter stray traction power currents that tend to leave the rails and seek alternative paths (such as underground utility lines) back to the traction power substation. Stray currents cause electrolytic corrosion whenever they leave one conductor (say a gas line) to leap over to another (such as a water pipe). Bad things happen when there's enough corrosion on an underground utility to cause a leak. Hence, the goal is to keep the traction power negative return current in the rails.

For the same reason, the negative bus of modern traction power substations are insulated from ground. The system is monitored at the substation and, if the touch potential between the rails and ground exceeds a safe "touch potential (about 50 volts), the negative bus is briefly automatically grounded. This is so passengers stepping onto of off the vehicle don't get a nasty shock. An exception is tracks within maintenance shops, which are usually deliberately grounded so the touch potential is always zero. There will be a separate traction power substation for the shop and insulated rail joints are provided at the ends of the shop aprons so the yard tracks remain ungrounded.

The problem with this is, while it's possible to construct railway tracks to be insulated from ground, it is virtually impossible to keep them sufficiently clean to maintain that isolation. As everybody on this forum realizes, railway tracks are dirty places. The degree of housekeeping that's necessary to maintain trackwork electrical isolation is extremely tedious and expensive. The corrosion control engineers, who insist on all of this electrical insulation, figure that's the track maintainer's problem, not theirs. But since there's never enough budget to fastidiously clean the tracks, some level of stray traction power current becomes inevitable.

Back in the old days, before there were products that could reliably insulate the rails (as long as they are clean) streetcar systems and other direct current electric railways typically provided "drain cables" that ran along the line and back to the negative bus of the substation. Any utility line that felt they were getting stray current on their pipes would deliberately connect to this cable to "drain" the unwanted electricity. They would also electrically bond all of the joints in their pipes so no corrosion would occur there. The problem with this approach is that the underground utility grid would often become a better negative return path than the rails were, thereby increasing the amount of current that would obstinately bleed off of the rails, into the earth and head for the nearest gas pipe.

/s/ Larry
Lawrence G. Lovejoy, P.E.

A locomotive electrical maintenance and safety instruction booklet that was recently brought to my attention is Canadian Pacific DL-269 "Locomotive Maintenance Electrical Handbook" published by their Mechanical Training Department. These are sometimes seen on eBay as part of retirees collections. It is all black and white printing, tab binding in older versions, spiral wire binding since 1997, with electrical system components covered on an item by item basis.

PC

Mr. Cook, is the DL269 an example of actual good or recommended practice, or does it contain appropriate 'safe working instructions' that aren't tendentious?

I will happily provide a scanned copy if it is a valuable resource.

(Out of curiosity, does the 1988 edition of "EMD GP60 Computer and Troubleshooting Guide" contain anything of safety interest in this context? I think most of the 'safety' there has to do with keeping the equipment safe from electrical charge on the employees, not vice versa, but this might be an aspect of increasing importance as stuff with microprocessor controls gets into preservation...)

The DL-269 is the guide for performing electrical inspections of locomotives in conjunction with their established periodic maintenance program. It is a very practical and well written document illustrated with basic but very good black and white artwork that was probably developed from photographs. It starts with preliminary inspections and instructions for setting up a unit in preparation for detailed electrical inspections. It then covers step by step the inspection procedure for each component. It then offers specific follow-up recommendations in the event that any problems are evident with the equipment. It is supported throughout with cautionary notices relating to proper workmanship and use of tools and equipment. I don't know if Canadian Pacific would ever allow reproduction rights to another organization, but there are enough of these in print that they are not rare on eBay. They show up occasionally and usually sell for reasonable prices. While it was obviously written for the EMD and GE locomotives on the system in the 1990's, it is has many sections that are a pretty good fit with the needs for a good electrical reference for shortline and regional railroads.

The EMD Computer and Troubleshooting guides for the Mod. 3 (60-series) computer and EM2000 are targeted pretty specifically at interpreting the failure codes and screen messages of the computer equipment, and are not so much about electrical safety. The bigger challenges for maintaining the 60-series equipment when and if they make it to preservation will be the very outdated equipment needed to service the system and the loss of the people who have the experience to teach it to others.

PC

Link to James Biddle (Megger brand name) page on a variety of topics pertaining to working safely with electricity.

http://www.biddlemegger.com/cgi-bin/web ... ation.html


Dave

'Railway Locomotives and Cars' had a comprehensive series of articles covering everything from the basics of electricity to system troubleshooting. The focus was on GE equipment, as the authors were GE employees.

Some of the articles were later published by Simmons Boardman in softbound book form-'Diesel Electrics...How to Keep 'Em Rolling.' I have seen this volume for sale on ebay.

Dave

Expanding on Mr. Ellsworth's mention of the 60-series locomotives, a look at the recent class schedule for the EMD Training Center shows that they no longer teach either the 50-series or the 60-series in their electrical class offerings.

PC

As a reference, I reviewed my copy of GE manual GEJ-3848 - "Electrical and Air Equipment Service Manual" for "Diesel-Electric Locomotive" (I think this is the August 1967 revision)

It was surprising to see how very little 'elementary safety' material appears in this manual, either in 'general' terms or in specific sections. I can find no discussion of arc flash in conjunction with any operations, and we're discussing maintenance procedures that include using the diesel engine to stone the comm in the auxiliary generator, and use of a welding power supply to test traction motors. (Here is a quote that will give you the general flavor: "To use the diesel-electric locomotive power plant, block all wheels except those connected to the motor being stoned. The motor can be run without disturbing the locomotive connections by placing the throttle in the first operating position. The current required to run the motor is so low that no damage will result to the blocked motors through which current will flow." This is immediately followed by safety warnings in all italic capitals, so you'll know they're important: Be sure to block those wheels; have someone in the cab to cut the power in case of problems; grinder must have PPE 'over face and eyes when grinding or blowing with compressed air' No mention about current or voltage while doing this grinding (!)

I guess that it was assumed that anyone a railroad considered qualified to work on these locomotives would already both understand and respect electrical safety. While I agree it might be simpleminded to include a full review of electrical-safety basics here, there are certainly a number of places (a fairly great number of places, where safety notes that involve personal safety rather than damage to equipment might well be provided.

It occurs to me that the way safety information is divided among training materials and service manuals is important, as is the way in which safety reminders are presented in context with 'easy access' to supporting methodology or detailed safety discussions when appropriate. Modern practice is probably to stress 'safety' by having everything, everywhere, fully noted -- and perhaps this is the result of much history in the past few decades being 'written in blood' rather than nanny-statism becoming more and more prevalent (and lawyers and underwriters more and more prominent in railroad cost administration priorities)

Where I see a potential problem (no pun intended!) is in reminding people of ordinary electrical hazards whenever they emerge during the course of maintenance procedures. If all we do is provide "NOTE: be sure power is disconnected before touching any conductive part or path" each time, it's going to become second-nature to read over it. now perhaps having to flip back and forth between pages or screens, to follow the actual procedure. That in itself is a couple of sources of added risk.

Let me put in a plug, again, for the joys of hypertext in an 'electronic' manual: there are several ways that 'danger!' might be incorporated into display as a given procedure commences (e.g. part of the text blinks in a different color or gives sound feedback) and full linking to both summary warnings and more-and-more-detailed discussion is easy to provide.

I suggest that we look into establishing 'electrical safety' guidelines for Becky's 'Best Practices' documentation, starting with precisely how we should structure safety information in manuals and other physical forms of documentation.

As someone who works with dangerous levels of electricity on a daily basis, let me make this plain:

No amount of safety crap will help if you don't understand the dangers involved. You can print warning after warning, but you must be aware IN YOUR OWN HEAD how dangerous electricity (or anything) can be. If you got someone working on this equipment who knows nothing more then to bounce from safety warning to safety warning, he is going to get hurt sooner or later. Breakdowns cause things to happen in ways that the safety warning can't predict.

Well said...

Nothing replaces substantial knowledge and experience. EMD SD70ACe's have an engraved plate in the cab explaining 'inverter discharge procedure.' Have to say that most of the shop folks never even noticed it.

Dave

Keep in mind that "back then" was not "the modern day".

"Back then", companies did not have whole staffs of people that went around making sure people sat at their desks correctly. Bridge piers did not have barrels of sand in front of them. Outlets did not have GFCI or kid-proof covers as new ones do. Most people worked in industrial work, which was inherently dangerous, and working around danger was an accepted part of working to earn a paycheck. Understanding the danger was part of the job, and the penalty for carelessness - getting maimed - was considered just. What else could happen? Everyone was getting by on thin dollar, there simply wasn't room in the economy to hand a lifetime trust-fund to a guy who got an arm smashed in a press. There were good family networks, and the family was expected to provide lifetime care to the invalid.

Suggesting that somebody work in "electrical" would be like suggesting they work in "radioactive" today. It was complex, scary and inherently hazardous. The workers were a cut above, and expected to know what they were doing. And most likely they came up through a long apprenticeship where the stupid got filtered out.

One of my friends back East is an EE for a major utility. I recall when I stayed at his house, he had some eye popping photographs of electrical jury rigging that he had encountered when working abroad.