For 50KV electrification, you’ld probably want a bit over 25’ above the top of the rail to allow for about 2’ of clearance between the contact wire and the top of a double stack as well as 2’ of clearance between the conatct wire and whatever is above it. Somewhere in my collection of papers I’ve got the clearance diagrams presented for the So. Cal. Regional Rail Authority hearings that took place in 1991 (this was well before I got married, so the papers are buried in some box somewhere in my garage).
Increasing clearances on overpasses will probably take up 50% of the cost of electrification in anything looking like and urbanized area.
AC electrifications present a lot less corrosion potential than DC electrifications (figure from 1924 was corrosion with AC was about 1% of DC).
I was thinking more of a modern main-line version of the North Shore battery electrics - the battery would provde power to the locomotive in areas with no cantenary (or temporarily de-energized catenary). Implementation would be similar to GE’s hybrid locomotive with a transformer instead of a diesel engine.
Erikem: Your metion of corrosion is intriguing. How does southshore and METRA electric’s maintenence figures compare with others AC operations and what items require this maintenance. Forgot about the corrosion problem and I understand what you are saying. Bet METRA and Southshore did not buy equipent for conveersion to AC operation. Does anyone know? Also the rebuilding of southshore cat is built for what voltage not the present (3000V).
Wouldn’t it be possible to place some sort of non-conducting shrouding material above the contact wire under overpasses, perhaps on the bottom of the overpass itself?
nanaimo: I’ve seen that is some places wood on old work and some kind of fiberglass or plastic on newer work. Do not like what may happen with wet wood.
One of the problems with higher voltages is induction currents, which can’t be eliminated except by elaborate shielding. I hope that there’s an electrical engineer among us who can explain this more thoroughly.
Just as soon as the federal government is willing to underwrite the cost (which may be never)…I don’t think any of the North American Class 1’s could afford to electrify on their own dime, even with the fuel cost issue…
Guys lets keep this post to the premise If RRs electrify. Use RR electrification in North America to discuss the pros and cons. That is really two different coins.
I don’t have any info on the relative maintenance costs of modern DC versus modern AC systems - a century ago, the maintenance costs for AC interurbans was significantly higher than the equivalent DC interurbans, but I would suspect that the maintenance costs are roughly similar now.
Metra and South Shore are still using 1500VDC, the CN line in Montreal (2400VDC) and the DL&W lines (3000VDC) both converted to AC over a decade ago. I think Metra/CSS&SB made the right choice in sticking with 1500VDC, saves the weight and space of not having a transfomer - inverters that can run off of 1500V are available off the shelf.
Corrosion protection is provided by making sure that any steel pipeline is a volt or more negative with respect to the soil. Also helps to have nonconducting sections in the pipelines.
Induction (at least magnetically induced) currents are driven more by the current in the line than the voltage - for a given power level, the currents will be lower at higher voltages and therefor should be less of a problem. On the other hand, a higher voltage allows for a higher voltage drop, which then allows for higher currents.
What higher voltage does have is a higher electric field, which can then lead to higher electrostatically induced currents - which shouldn’t be much of a problem unless you are really close to the catenary.
There’s another induction related problem when the electrified track is paralleled by a nearby power line or telephone line. At close distances, the magnetic field from the catenary isn’t fully cancelled by the field induced by the return current in the track (and the problem is worse when some of the return current flows through the ground). This will induce a voltage on the nearby power or phone line, but the problem can be minimized by transposing the conductors on the neighboring lines (the twisted pairs in telephone cables are especially effective).
Well, if I had to take a stab…I wouldn’t be surprised if mainline electrification gets a start in California. While I realize there are plenty of reasons why I’m going to be wrong (just by picking a state the odds are 1:50 against me), here are a few reasons:
A limited area with high (for the US) frequency passenger train service-San Francisco/San Jose/Oakland/Sacramento. The state may be willing to pony up some money toward the project. After that, the UP might be willing and able in the future to add their own extension as far as Roseville and operate an electric division from there to the port of Oakland for a manageable cost.
LA area commuter service, plus over the mountains to Needles, Bakersfield, etc. A bit more complicated since there are more routes (and no one will want to be left out) but a combination of grades and traffic (and air pollution) that might make electrification a project that the state would contribute to.
Makes sense to me. How about L.A./Union down to San Diego? It’s a fairly heavy Amtrak corridor and there’s the possiblity of all those suburban-type services going on the cat. too.
I found this paper on electrifying 42,000 route miles in North America, including cost estimates and time frame for transition. I already posted the link on the “Electrification in North America” thread.
Edit: Didn’t realize the author of the paper at the above link was a LaRouche follower. I do not neccessarily endorse the political/economic philosophy put forth in the last paragraph of the paper, but the estimates of capital investments neccessary are fascinating, if you disregard the mag-lev proposition.
erikem: Go to the web site for caltrain and look up their electrification statement I believe the technical aspects are in Chap 2.1 that covers both EMI and EMF. Very deep reading and their figures are for 2003 and the per mile is a lot less than I’ve seen quoted. 2008 will be higher. Of course their route only has two sharp curves.
Using Europe as an example, mainlines are electrified, but only a few branchlines with important (high volume) freight customers are. Yards are switched/humped using diesels, with only the receiving/departure/engine facility tracks electrified.
As far as clearances are concerned, IIRC the caternary in Philadelphia at 30th St. Station and at PHL Airport is strung very low, at the most 2 feet above the roof of the motor, and I never saw any arcing, even in rainy weather.
German DB recently electrified a double track mainline close to where I live. The foundation supports for the poles, the poles themselves and the insulators and supports for the caternary went up trackside, so crews worked without disrupting service. The transmission line itself was strung up at night with minimal service disruption.
Just wondering, if you had wide track centers, couldn’t you make due with just one support pole between the tracks? Wouldn’t that save at least some money?