Main Line Electrifications

[Anonymous]

There are more advantages to the 25 kV/50 hz system then just industry standard (despite the fact that it cuts the cost right there - off the shelf equipment rocks).

Higher frequencies mean smaller transformers - good for EMUS when you want to mount a transformer underfloor (and keep the weight down).

Higher voltage means less substations. 3 kV system capable of 6 MW output requires something about 3 mile substation spacing. 25 kV will happily work with 30 miles. The reason why BMLP or Sishen-Saldanha run at 50 kV is because it saves the substations. I believe that whole BMLP is fed from a single 'outlet' :D. (BTW whole 600 miles of sishen-saldanha use just 8 substations - voltage may drop as low as 25 kV between then) Obviously these are giant saivngs.

And lastly - higher voltage means less maintenance and machinery for the catenary. 3 kV system pretty much requires two contact wires - while 25 kV will work with a single one - and of a smaller diameter.

Once multi-system equipment starts to be widely avalible there will be a giant pu***oward 25 kV/50 Hz system all over Europe (esp in DC countries).

BTW Poland (and a few other countries) had chosen 3 kV DC because Germans used 15 kV 16,6 Hz system. It was 1935 then so obviously it was a national defense issue :)

BTW - in the case of the US the 50 kV transcons and 25 kV everywhere else would make sense. But frankly - I can't really see a justification for the expense in the current operating schemes. Wires provide benefits that would not be used by US freight railroads.

[MichaelSol]

QUOTE: Originally posted by uzurpator

3 kV system capable of 6 MW output requires something about 3 mile substation spacing. 25 kV will happily work with 30 miles.

Milwaukee Road's 3600 vDC substations, which had continuous ratings typically of 4.8 MW or 7.2 MW, were all spaced 28-30 miles.

Best regards, Michael Sol

[MichaelSol]

QUOTE: Originally posted by uzurpator
Obviously these are giant saivngs.

Still nervous when engineering cost analysis is structured entirely on words like "giant."

With 1973 technology, rectifiers and inverters, Milwaukee Road studies found that 25 kv Ac and the 3600 vDC systems cost approximately the same to operate. While there were endless arguments about the idea that AC "should" cost less to operate, in fact it didn't. We looked and looked.

The difference in construction costs were small .... DC cost about 10% more, overall, to construct at the time. For existing DC systems, we could find no economic incentive to change systems unless someone just wanted to spend a lot of money for political reasons. And that was the bottom line when we actually looked at numbers ... replacing an existing DC electrification with an AC system invariably generated a negative rate of return unless you could obtain the money for free.

This is the single reason why Italy did not convert to 6kV DC and why most nations have been extremely slow to convert to an AC "standard" that affects, at best, a few international trains. While there are operating advantages to both the higher voltage DC and the AC, they simply were not worth the cost of replacing the existing systems. That is, nothing is realistically being purchased that justifies the cost. Holland has a unique situation of a system operating right at capacity for which a hgher voltage something, DC or AC, is the only feasible solution.

For a long system tapping from multiple AC supplies, the "clean" nature of DC avoided both loss of phase and phase problems as trains ran through power from those multiple suppliers. For existing rail installations, safety clearances came down in favor of the DC systems.

DC has evolved considerably since the early 1970s. DC is now the preferred means of long distance high voltage power transmission. Inverter and rectifier technology has improved by leaps and bounds, and their costs have dropped substantially. I suspect that the small advantage that AC systems had in construction costs thirty years ago has disappeared over shorter distances. At very high voltage, DC now has the cost advantage at transmission distances of approximately 400 miles or more and this cost advantage increases with distance. Likewise, DC's superior utilization of the carrier cross section reduces power losses and increases transmission efficiency substantially over AC.

As hgh voltage AC supply lines are gradually converted over the next twenty years to high voltage DC, the irony will be that rail systems which are utilizing AC at any voltage will be stranded.

They will have to invest in inverter and rectifier substations. At that point, the construction cost advantage will clearly be with DC railway electrification and AC will be viewed as an archaic and expensive albeit interesting relic.

Best regards, Michael Sol

[arbfbe]

QUOTE: Originally posted by futuremodal

QUOTE: Originally posted by arbfbe

To feed trailing diesels from a lead electric would require quite a substantial bus system. The spring loaded bars on the GN Y -1 class electrics come to mind. There are some problems with that between units account the high voltages in the areas where crew members are working. The MILW boxcabs did bus the power between units but those units were almost permanently coupled and the feeders were above the roof line.

As I percieve such power MU'ing, the combined electric and diesel loco lashup would act as each other's road slug depending on which power source is being utilized. Road slugs don't need such heavy duty bus bar connections, right? If I understand correctly, the bus bars were used to transmit "unconverted" 3600v DC current to the trailing units, while a road slug connection transmits "converted" current to the trailing unit(s).

QUOTE:
All the opportunities MILW management had to make their railroad work and they repeatedly chose the wrong course.

Can you be more specific? For posterity's sake, what would you have done differently regarding Milwaukee's decision nexus circa 1970 as to what to do with the electrification, save it, scrap it, modernize it, and/or expand it?

My long held belief was that Milwaukee should have scrapped the catenary back in the 1950's when dieselization became commonplace, e.g. the inherent savings of standardization. That belief has been modified in recent months with the information provided on this forum regarding the operating cost savings of electrification and the seemingly permanent price increases in diesel fuel, to the point where I now think electrification of certain segments would have made sense if a bi-modal power solution could be had "on the fly", e.g. some sort of emulation of the FL9 concept. For the Milwaukee in the 1970's, that FL9 technology concept existed in conjunction with Milwaukee's own innovations in running diesels and electrics together. Perhaps Milwaukee should have kept the wires between Harlowtown and Butte, as well as Haugen and Avery, but also considered taking down the wires between Butte and Haugen since that was basically water level gradient. On the Cascade segment, keep the wires between Beverly and Kittitas for the Saddle Mountain crossing as well as between Hyak and Maple Valley for the Snoqualmie Pass grade.

*********************************************************************************************

The problem with the bussing of power from a single source are many fold. Note the slug units you refer to are commonly a single unit feeding one or both ends of the slug of diesel powered locomotives. We are talking 600v DC with a max of about 1000 amps per traction motor on the slug. That is still a lot of watts to carry through the wires. Now carry that over to your suggestion for the MILW and you are looking for the head end electric to provide 3000+vDC to 12 or 18 trailing traction motors if they are electric locomotives. But they would be diesels, with 600vDC traction motors which the Joes could not provide. So in all likely hood, you would be building a new class of 600V DC electric units to lead the trailing diesels. It would be far simpler to build a new class of diesels with pantographs with 3000 volt traction motors. However, that would mean a complete redesign of the units to these specs using non-standard main generators, traction motors and control circuitry. Prohibitively expensive and far out of reach to the MILW. Also, trying to feed three or four locomotives from one pantograph just begs to have an arc between the pan shoe and the trolley wire in the heavy frost which would burn through the wire causing massive delays until the wire is repaired.

There is just not likely any feasible substitute for an existing electrification than to build purely electric locomotives for the line voltage in use. Changing DC voltages in the MILW era would involve motor generator sets on each locomotive if the 600v traction motors were retained which would have made the diesel units too heavy for the bridge structures on the MILW. The ideas of short stretches of line with electrification in mountain grade territory seems to run counter to rebuilding the entire existing electrical system in it's entirety to more fully utilize the specially built electric locomotives that would be necessary.

Now as to poor business judgement by MILW managers at the highest levels...
The topic that has arisen on this thread is the idea MILW could have had a total upgrade to the electrification to state of the art standards at NO COST to themselves. What a deal! Instead, they elected to pass on that gift horse. The reason I have heard was the proposal from the consortium included GE and there was a clause that the MILW could only purchase their locomotives from GE during the first 20 yrs of the contract. While it would be unlikely EMD or any other supplier would design a competing locomotive at a competitive price in that time and the life span of the original electrics could easily exceed that 20 yr period, MILW management was unwilling to accept such a restriction. Come on now, someone offers to build you a new house for free and the only restriction is the next two cars you buy have to be Fords and you walk away from that offer?!?!? Is that short sighted or what?

As to the other chances the MILW management had to redeem themselves, I can refer you to the previous threads you have participated in on this forum. Specifically the Booz, Allen & Hamilton assessment that the profits were in the long haul including the Pacific Coast extension and not in the granger lines of the MILW. Yet, MILW management abandoned the profitable lines and kept focused on the lines that were losing them money. You can search the other MILW threads on this forum to refresh your memory if you like.

What would I have done with the electrification in the 1950's and 1960's? Expand it, of course. Each MILW boxcab has the same rating as the current F, SD or GP 9 series units of the 1950's. The Joes, at 5500 hp were equal to almost 4 GP9s in mu. It would take the diesel builders until post 2000 to come up with a single prime mover of 6000 hp to best the Joes. (The DD series of UP units do not count as they are just two diesels on a single chassis. All the eliminated was the drawbars between two units.) The Black Mesa & Lake Powell units of the1970s were far ahead of the diesels of that era. There were serious alternatives to motor generator types of substations that the MILW could have used to increase the load capacity of the electrification of the existing lines at a far lower cost than building mg substations. So I say, electrify the gap in Idaho, replace the trolley poles using concrete or steel structures and buy new locomotives. Leave all the diesels save for branchline power east of Harlowton until you can electrify the rest of the mainlines. If the power companies and suppliers will do this for you at no substantial charges to yourself, welcome them into the board room with open arms.

Unfortunately, MILW management was bent of getting out of the railroad business by merging the MILW with any other railroad that would take them. Their primary choice seemed to be the C&NW which was not the strongest line in the pile. In order to make themselves more attractive to a suitor, the managers decided that standardization was desirable and electrification was nonstandard no matter how well it worked. Well, Plan A with the merger scenario did not work but Plan B, make the MILW the best transcontinental line to Seattle using other people's money to upgrade the electrification was dismissed in favor of pursueing Plan A2, A3 and finally Plan C, dump the money making parts of the system to look again at Plan A3, A4 and who knows how many other merger related ideas. The one finally pursued with relish was inclusion into the BN system since BN was required to consider it as part of their original merger authority granted by the ICC. On it's death throes, the final Plan A was with the GTW but the Soo Line snatched that opportunity away. Instead of the MILW lines being abandoned in the midwest in favor of the merged railroad's trackage, it became a situation where the Soo Line trackage was abandoned and spun off in favor of the MILW lines. Yes, indeed what happened was the SOO Line managers came to run what was left of the MILW granger lines.

[Anonymous]

arbfbe,

Thanks for providing your insights into the Milwaukee electrification decisions. I have a few followup questions (and Michael Sol, please chip in if you want):

1. Was there any significant difference between the current used by the New Haven et al with their FL9's and the 3600 v DC used by the Milwaukee that prevented them from utilizing an FL9 type locomotive on the PCE? Did the Milwaukee ever consider an electric/diesel hybrid like the FL9 for the PCE? Do you know if the FL9 was a considerably more expensive locomotive than standard diesels or an electric like the Little Joes?

2. With regards to the possibility of fulling electrifying the mainline from Harlowtown to the Puget Sound, when the Milwaukee received trackage rights into Portland, wouldn't that have put a crimp into having a dedicated electric fleet west of Harlowtown? You can't put catenary over someone elses track. If as I had speculated the Milwaukee could have requested (and received) trackage rights over the SP&S between Spokane and Portland as well as the I-5 corridor, that also would have required a substantial fleet of diesels in the PNW. Any run through freights would have to have been fully dieselized or run in electric/diesel combos, so there would be the added cost of adding/taking out electrics at certain points in the case of the latter. And since mergers were an ever increasing fact of life for the railroad industry, there is some credibility to the argument that the uniqueness of the electrification may have scared off potential suitors, especially in an industry that practically worships at the alter of standardization.

Don't get me wrong, I believe in hindsight that for the Milwaukee (or the GN for that matter) to have given up on electrification was a bad idea, given today's diesel fuel costs (and BNSF's current capacity constraints through the Cascade Tunnel). If either entity had kept their electrification (and assuming the Milwaukee had survived into the present), said electrification would be paying huge divedends right now.

[CSSHEGEWISCH]

Although dual-mode (FL9-type) locomotives to cover a tunnel-type electrification sound like a good idea to improve utilization, they still have their limitations. Amtrak generally does not allow its P32's to stray beyond Albany, which pretty much restricts their range to not a whole lot too far beyond the end of third rail. Dual-mode locomotives on a tunnel electrification could not be allowed to stray too far from the mainline that has the tunnel, which would restrict their utilization to some extent. They would also be more expensive than conventional diesel-electrics, which would make it hard to justify their purchase when their operating range would still be restricted.

[jchnhtfd]

Pause for thought...

The considerations for using AC vs. DC differ depending on whether one is talking about transmission, distribution, or powering motors.

First, transmission. Until relatively recently, AC was the only form of electrical power which was really usable for transmission. Why? Because it is possible to transform AC from one voltage to another using a simple static device: the transformer, which is dead simple, highly reliable, and very very efficient. And it is necessary, economically, to use very high voltages for transmission, since power losses are inversely proportional to the square of the voltage -- but you don't want to either generate or use electricity at high voltages. More recently, solid state converters have come into use for conversion of AC to DC, or vice versa, at very high voltages. With these converters, which are not cheap and are nowhere near as reliable as transformers, it is possible to get the advantages of very to extreme high voltage transmission of power with DC, which has some real advantages.

For local distribution -- say in a city -- I do not see an advantage to DC, if for no other reason economics: you still need moderately high voltage for distribution (23 kV is typical) but you don't want that in the individual user's establishments (anything over 480 is regarded as very high in the user's environment, and takes special handling). So each user, or group of users, would need the converters rather than transformers.

For power use, the advantages of AC are almost overwhelming for most applications. A three phase (or single phase, in small applications) AC motor is, again, a near zero maintenance, dead simple, device. A DC motor is neither.

Railroad applications are just a wee bit different. First, although there were a very very few multi-phase AC overhead systems, they were horribly complex and difficult to maintain, so you were limited to single phase at some frequency or other (it really doesn't matter, within reason). But large single phase AC motors aren't practical, so the railroads used DC traction motors. In the bad old days, this meant motor-generator sets to convert the AC (stepped down via a transformer) to get DC. Some outfits ran the numbers and decided that complexity wasn't worth it, and used DC for distribution -- with lots of substations. Others decided that it was, and used AC at much higher voltages (like 11 kV) for distribution. Again, however, solid state devices get into the equation, and with them it is now quite practical, and 'best practice', to use solid state devices to take either DC or single phase AC, at some voltage compatible with the catenary or whatever, convert it in the locomotive to DC, and reconvert it to frequency controlled three-phase AC to drive the traction motors.

Do you use AC or DC for your power distribution (catenary/third rail)? That would be a decision grounded in economics. My bet would be that in most cases, AC would win, if you were starting from scratch. If you are using existing infrastructure -- run what you brung.

[Isambard]

QUOTE: Originally posted by uzurpator


BTW Poland (and a few other countries) had chosen 3 kV DC because Germans used 15 kV 16,6 Hz system. It was 1935 then so obviously it was a national defense issue :)

By choosing 15 kV 16,6 Hz, German equipment would be prevented from running on Polish rails in the event of an invasion? Was it in fact a consideration in the Polish decision? In view of the predominance of steam power at the time I would have thought that this would not have been a significant consideration.

Apart from that can anyone comment on the use of 16,6 Hz transmission by Germany rather than a higher frequency? Was this an inheritance from the early days of AC transmission? Was use of 16,6 Hz general elsewhere? Is it still used?

As an aside, I understand that Ontario Hydro choose 25 Hz over 60 Hz for domestic purposes in the early days of AC, due to concerns that 60 Hz was more dangerous to personnel and customers. As a result in the 1950's Ontario had a massive project to convert all domestic and industrial equipment in southern Ontario from 25 Hz to 60Hz, the by then prevailing standard in the rest of Ontario and North America. Think of it-every vacuum cleaner, refridgerator and so on!

As other questions for anyone:
What is/are the source(s) for electrical power for the Dutch railway system- fossil fueled power stations or nuclear, domestic Dutch or imported?

Is the transmission frequency for electrified North American railroads usually at 60 Hz, the standard domestic frequency?

[Hugh Jampton]

16 2/3 Hz was originally chosen as it's easy to make, being 1/3 of 50Hz,, and commutated motors will run at this frequency, which means that simple resistance control can be used.

[martin.knoepfel]

Hugh Jampton is right. When Germany started electrification, 50 Hz didn't seem practicable for railway purposes. Germany, Austria, Sweden, Norway and Switzerland run on 15 kv 16,7 Hz AC. The Swiss federal railways recently admitted, they would use 25 kv 50 Hz AC, if they could start from scratch. However, Hungary successfully tried out 50 Hz very early, in the twenties or thirties of the 20th century with the Kando engines.

I know of natural-gas-fired and nuclear power plants in the Netherlands.

[arbfbe]

The easiest way to regulate the speed on an AC motor is to vary the frequency of the current. Today there are different alternatives. I believe the N&W AC system in it's earliest forms had units that had three throttle positions, stop, half speed and full speed. Imagine the lunging between throttle postions there! I suppose the speed control was the reason for the low frequencies of some systems.

[Anonymous]

MichaelSol:

I will auto correct myself. Spacing on the polish system ( 3kV dc) is between 5 and 20 miles - depending on the traffic density. Typical substation is about 4,5 MW continuus and currents may reach 2,6 kA when ET42 (6600 hp) class loco is working hard.

Considering that a single Little Joe was 5500 hp - that is about the same - buuut - with longer substation spacing (28 miles - as yau claim) the loss of voltage might be higher. I suspect that currents could go up to 3 kA then... impressive to say the least.

As for the 'giant' savings. Maybe the better word would be 'substantial'. Electrification pays off when the line is havily trafficked. With longer segments and euro-style traffic density (think 3 minute headways) with longer segments there are, ferinstance more chances to regenerate energy. If one really tried then 25 kV would suffice for 200 or so miles - with low enough traffic density. BTW - spacing of 25 kV system is about 40-60 miles.

But nonetheless - in the US type of railroading electrification does not make sense at all. The traffic density is too low (there are too few places with really tight spacing), trains are, by euro standards, underpowered and speeds are moderate.

EDIT: as for clearances - what is the problem to step down from 25 kV to say - 8,33 kV? That would be the same as clearances for 3 kV DC.

Isambard:

When polish electrification was coined there was a plan to electrify a coal line from Upper Silesia to the Gdynia seaport - in that tume that line run along the border with Germany. Also - electrification started in 1935 - the war started in 1939. By 1939 there were only 8 locos and several EMUS in service. Obviously later it was a moot point.

When the war ended communists simply started with what was there - so 3 kV DCsystem was there to stay - esp since the BIg Brother also electrified with 3kV DC

[gfjwilmde]

I've read some of your messages and it has me confused. Although I'm a machinist, I've also been in some training classes learning about electricity(for safety training[required]). My understanding about the subject is, that it's easier to move(transport)electricity when it's ac rather than dc. I was taught that you can dump up ac to a higher voltage than dc, thus making it better to transmit across greater distances. Another thing I've learned in the 12+ yrs that I've been working around electric locomotives is that all they are no more than converters and 'step down' transformers. Ac cannot be used directly to the traction motors because of the pulsations in them. So the converters change ac over to dc and at the same time smoothes out the pulsations. Once this is done then its changed back to ac(or stays dc) and then 'stepped down to a safe and usable voltage for the traction motors. In fact...many of your modern diesels operate similarly. The diesel locomotive's generator(altenator) is actually producing ac current and is changed and 'stepped down' silmilar to what I explained earlier. The one downside to European or Asian rail systems is this, their electric locomotives are very lightweight. Most of the electrics barely weigh over 100 tons. Trying to pull a heavy train with those is an effort in futility. On the other hand...when electric freight operations were in their heyday, many of the railroads had very big, very heavy and very powerfull(at that time) electrics pulling most anything with very little in the way of mu'ing. Anyway...I believe there should have been an extensive network of both diesel and electric rail lines in this country ages ago. Many of the northeastern cities were very concerned about pollution caused by the steam locomotives, so railroads like Pennsy and New Haven electified much of their eastern or urban territories to cut down on smoke emmissions. Well, don't think for one minute that diesels don't put out a significant amount of fumes either. That's one reason why there should be more use of electric rail lines across the country than ever before. Surely...there are many in urban areas whom have no choice, but to live near(or right next to) an active rail line that has significant traffic flow. Surely to hear the rubble of the high horsepower diesels and the stench of diesel exhaust as they blast(or crawl) through a residential area is very uncomfortable. Sometimes, the smell of the exhaust lingers long after the train has departed. No to mention if the train is just sitting there waiting for traffic to clear so it can be on it's way is very inconsiderate to the surrounding populace. When I was a teen, I used to hangout in the Conrail yards near Jersey City, New Jersey. Many of the trains crept through the city, usually blowing out huge plumes of smoke, blackening everything around. Sometimes, if there was a cylinder that was bad, there would also be oil flying out with the exhaust as well. Yes...maybe some day we'll return to moving heavy freight trains with electics again...some day.



GLENN
A R E A L RAILROADER!!!!!
A R E A L AMTRAKER!!!!!

[ungern]

This makes me ask a question.

How about the railroads electrifying their yards? This minimize the expense with much of the benifits because isn't yard switching a big use of diesel fuel. Already railroads are beginning to buy "green goats" for yard switching because they're more effecient why not take it a step further and just electrify the yards and leave the line for the diesel-electrics?

Ungern
BNSF fan

[Anonymous]

Switching - about 0.00000005% of fuel used by railroads

[TH&B]

Ungern;
I think that's a very good question, I've never realy thought of that. I think the fuel used by railroad switching is actualy alot and wastefull and in fact CPRail recently quoted that their switchers are killing them in fuel. Railroads are always using older downgraded diesels and "double switching". If switching costs could be reduced railroads could maybe compete better with shorter hauls.

Just electrify the yards with DC I suppose and use very simple switchers with pantographs.

But please don't suggest to use 3rd rail hehehe, for the swicthmens sake.

[ungern]

Actually, I won't ever suggest 3rd rail in a switching yard.

Also hi voltage transmission lines running alongside the mainlines could allow the railroads another income source. Amtrak actually makes money by allowing open access of its transmission lines that power the NEC in the wholesale electricity market.

Uzurpator, where did you get the 0.00000005% number for amount of fuel used while switching?

Ungern

[Anonymous]

QUOTE: Originally posted by CSSHEGEWISCH

Although dual-mode (FL9-type) locomotives to cover a tunnel-type electrification sound like a good idea to improve utilization, they still have their limitations. Amtrak generally does not allow its P32's to stray beyond Albany, which pretty much restricts their range to not a whole lot too far beyond the end of third rail. Dual-mode locomotives on a tunnel electrification could not be allowed to stray too far from the mainline that has the tunnel, which would restrict their utilization to some extent. They would also be more expensive than conventional diesel-electrics, which would make it hard to justify their purchase when their operating range would still be restricted.

That was one of the things that pops to mind. However, there are two different subjects I want to broach regarding the FL9 concept: (1)Why the Milwaukee did not consider an FL9 type locomotive, and (2)if an FL9 type solution would work to allow more capacity through the Cascade Tunnel.

1. My thought regarding the Milwaukee circa 1970 was that they were faced with an electrical physical plant that needed to be upgraded (and possibly expanded) or eliminated. With a bi-modal locomotive such as the FL9, they could have eliminated much of the catenary over the more water level grades such as the Clark Fork segments without having to establish new crew districts and locomotive transfer areas. This way they could have focused on upgrading only the mountainous segments of the electrification at a fraction of the cost of upgrading or expanding the entire electrical physical plant.

2. For the current Cascade Tunnel, one would have to balance the cost of rostering FL9-type locomotives that are limited to a small geographic area against the benefits of increasing capacity, perhaps doubling capacity over Stevens Pass (aka no time delays to ventilate the tunnel). I also wonder about clearances in the Cascade Tunnel, whether one can even restring catenary without interfering with double stacks, or whether the third rail option might work (at least in the tunnel).

[arbfbe]

futuremodal,

While the FL9 concept was a nice idea you end up with expensive units that spend a lot of their time outside the electric zone where all the high priced dual mode equipment goes to waste. That is not a great way to utilize capital. It worked on the NH account the units were into the electrified trackage every day. Now think about the MILW. The dual use units leaves Tacoma and works over the Cascades and in your secnario only on the short sections of mountain grade. Full diesel through Idaho to St Paul Pass where the dual use pantographs are raised. Then out of trolley from Haugen to Butte where the pans go up again for the mountain. Then no pan use all the way to St Paul or KC. So you might as well cut them off in Harlo and turn them back. So they become restricted use units in which case you might as well buy straight electrics for the lines west of Harlo.

The NH was an ac railroad while the MILW was dc. None of the equipment would have been interchangable. The FL9s worked since the third rail was compatible with the diesel traction motors. They were not compatible with the catenary with it's ac voltages.

The measure of work for electricity is Watts. You get watts from multiplying the volts times the amps. Volts is the pressure of the electricity through the system and amps is the volume of the electrons through the system. Now you can get 100 watts of power in any number of ways so long as volts x amps = 100w. P=IxE if you remember your high school physics. If you have 100 volts you only need to shove 1 amp through the iwres to have 100 watts. Or you can use 1 volt to move 100 amps. That 1 volt does not move too much through wires though since the wire has resistance. The 100 v option is better for over coming the resistance of the wire. Since you are only trying to move 1 amp the wire does not have to be very big, you are not trying to move a lot of volume.

On the users side, high voltages are a problem. With all that power they need a lot of insulation to keep Readdy Kilowatt coralled where you want him. There it makes to use bigger wires for a shorter distance to get the work done. The MILW AC supply to the substations was pretty small wire compared to the copper feeder on the trolley poles that brought power from the substation to the catenary. The dual catenary was about 4' or wire to make a pound of copper while the dc feeder at the same 3600 v DC was about 4# of copper for every foot of wire. So it took about 4.25 lb of copper for every foot of railroad to feed a couple of trains at a time. On the other hand, the AC commercial lines fed substations, small towns and other rural areas.

Another argument AC proponents hand out is since the AC cycle goes positive to negative with each cycle change the line system will break an arc while the continuous nature of the DC will hold the arc until something burns through or a breaker kicks out. The DC proponents will say how that same factor means you have a period at each cycle change where there is not any pu***o make work. The AC people developed multi phase AC to counter that short coming.

At one time the AC vs DC arguments were just as strongly argued as the standard gauge vs narrow gauge battles. With today's technology i doubt there is all that much difference with a newly designed system in either mode. The big battle is to get someone to make the investment. The saying goes ithat electrification is the program every one wants to be the second company to take the plunge.

[Tulyar15]

QUOTE: Originally posted by ungern

Actually, I won't ever suggest 3rd rail in a switching yard.

When the Southern Railway in England embarked on its big electrification programme in the 1920's and 1930's, it used 3rd rail and only passenger trains were electric (all worked by EMUs). When WW2 broke out, shortage of good quality coal prompted the Southern to build some electric locos for freight trains. Because it would be impractical to have 3rd rail in switching yards, the yards concerned were equipped with simple trolley wire. When the lines from London to the Kent Coast ports were electrified on 3rd rail in the 1950's more yards were wired and more locos built with both pick up shoes and pantographs. But in the 1960's a class of locos called "Electro Diesels" which were basically electric locos with a small (600hp) diesel engine on board were built. These proved to be much more useful than the straight electric locos which were then scrapped and the yards de-wired. But now Brush are fitting an old Class 86 electric loco with batteries to provide a more eco-friendly alternative to the Elector-Diesels, a few of which are still running.

[Anonymous]

ungern: i used a hyperbole for the fact that fuel used by switching is insignificant to the cost of electrification... ;)

Think about it - UPRR Bailey Yard has 315 miles of track. Wires cost ~1mil/mile. So to electrify you'd need to spend $315 million. That money will cover switching in that yard for several hundread years ;)

[Anonymous]

No one has touched on one of the biggest impedements to the economies of electrification in the US, namely property taxes. Electrification significanly raises the real property value and thereby the taxes. For anything less than very heavily used lines any reduced operating costs resulting from the use of electricity will be spent on local property taxes. And this is totally ignoring the interest needed on the loans to pay for the infrastructure, which in a few areas of the US invokes another set of taxes.

There are two notable exceptions to the above. The electrified railroad can be a government or quasi government agency, as Amtrak , SEPTA, NJDOT, and the like. They are generally immune from taxes. This was the case in much of Europe until recently and is still the case in places. The other exception has been utilities who could until recently automatically pass on their costs to the consumers and thus had no real incentive to find the true lowest cost solution.

[MichaelSol]

QUOTE: Originally posted by uzurpator

Spacing on the polish system ( 3kV dc) is between 5 and 20 miles - depending on the traffic density. Typical substation is about 4,5 MW continuus and currents may reach 2,6 kA when ET42 (6600 hp) class loco is working hard.

Considering that a single Little Joe was 5500 hp - that is about the same - buuut - with longer substation spacing (28 miles - as yau claim) the loss of voltage might be higher. I suspect that currents could go up to 3 kA then... impressive to say the least.

Milwaukee voltage drop could drop as low as 2400 volts between substations. A Little Joe might be pulling as much as 1800 amps IF it was working hard. The locations of substations was such that usually at that distance, Joes would be working on flat ground, with a couple of exceptions. But, naturally, the substations tended to be located on Mountain grades, with slightly closer spacing.

Two Joes could pull 3600 amps if the voltage dropped to 2400 volts. DC systems, however, generally pair substations, whereas AC splits the power sources so phase is not a problem. Indeed, with the DC system, three or more power supplies can be fed to one train if necessary.

On DC then, a typical power pair, Drexel and East Portal substations on the Rocky Mountain Division, have a combined capacity of 12 MW, to feed an energized section. At one hour overload on this 28 mile section, the capacity is 24 MW. For two Joes using 3600 amps, they have available to them 5000 amps, with an overload capacity of 10,000 amps. Big power, but it is carried on that section by 1,000,000 cm of direct contact wire, 500,000 cm of copper feeder cable, and 750,000 cm of aluminum feeder, for a total of 2.25 million cm of capacity.

It was routine to have as many as four Little Joes drawing from an energized section of track. Of course, if one set was going uphill and one downhill, the downhill set was generating power of its own into the trolley system, and represented an additional source of power for the uphill train.

The ability to raise and lower trolley voltage at the substations enabled more efficient movement of heavy trains, sometimes it was useful to deliver less than 3600 vDC to the engines.

The DC design was simply rugged. The fact that 80 year old 3000 vDCsystems continue to operate on more railway mileage than just about any other form of electric traction it testimony to both their economy and reliability.

GE had tested a 5000 vDC design for the Milwaukee. The only reason it was not used was economic. The cost savings of copper cable permitted by the higher voltage was more than offset by the hgher costs of manufacturing the locomotives to operate at that voltage. The 3,000 vDC resulted from the intersection of two cost curves, nothing more.

The DC traction motor was, at that time, far superior to anything else. The use of relatively low voltqges DC, compared to AC, was primarily a historical artifact that no longer exists: the difficulty of converting DC voltages from one to another, compared to the ease of converting AC voltgages. That problem no longer exists. For any benefits of any particular voltage insofar as distance of transmission is concerned, AC and DC now compete on relatively equal terms.

The modern AC motor ostensibly changes the equation a bit, but the bottom line is that an AC "locomotive" is now a substantially more complex machine than its DC counterparts, and regeneration remains an expensiive option with AC, whereas it is an inherent design benefit of the DC systems. This was something we noted: AC locomotives appeared to have shorter economic service lives than standard DC equipment.

Note that DC diesel-electric locomotives sell at asubstantial price advantage to AC locomotives, notwithstanding that the AC design is not "new". This no doubt remains true for electric locomotives as well. And, as Alan points out, anything placing voltages on the order of 20k, 25k or 50k directly into the confines of a locomotive body shell that is then converting that power to DC and back to AC again, represents a lot of high voltage activity in a very small space.

Russian Railways reports 56 empoyee deaths per year related to electrification -- as opposed to other railway related causes -- apparently most of them occuring on AC sections.

However, future planning does not seem to account for the fact that 100kv, 200 kv, 350 kv and 500 kv AC supply sources will not be available in the not-so-distant future, as these lines are converted to DC for its inherent long distance transmission efficiency and environmental advantages. The advantages that the Transformer gave to AC systems will be gone entirely, as AC rail electrification will almost certainly have to incur the expense of rectifier substations rather than transformer substations, and the additional cost of inverters if they care to regenerate back into the power grid.

Once again, rail planners may be preparing for the past, rather than for the future.

Best regards, Michael Sol

[jchnhtfd]

Just a few little comments here...

The AC traction motor is far simpler than a DC traction motor, and has almost overwhelming advantages. If this were not true, there would never be such a thing as AC diesels with their higher price tag. Railroad equipment purchasers and maintenance personnel are not fools...

Multi-phase AC was NOT invented to solve the 'problem' of 'no push' twice each cycle. Multi-phase -- most usually three phase -- power was developed to address the problem of starting an AC motor; a single phase AC motor will not, without auxiliary devices, start on its own (although it will keep running very nicely, thank you). Without getting all Steinmetz here, suffice it to say that with three phase power, you can get a very nice rotating magnetic field, which will drag a rotor (which can be unbelievably simple) along with it, with about as much torque (and power) as you want -- and if you can control the frequency, at any speed you want. This is what modern variable speed drives, such as are used on AC diesels and electric motors, do: you control the torque by the current in the field, and the speed by the frequency supplied to the motor. Wheel slipping? No problem, my friend -- reduce the current slightly. Want to go faster? No problem -- increase the frequency (and current). There is nothing complex about any of it, and maintenance is dead simple -- something fries, pull the board and slip in a new one.

I am sorry that Michael feels that those of us in railway engineering are planning for the past, rather than the future; I'd very much rather not think so... and, in terms of on-board equipment, I'll stick with my alternators, static converters, and AC motors for the time being -- if I never see another commutator again, it's going to be way too soon!

[greyhounds]

I'd reccomend a back copy of "Railroad History #181" - autumn 1999 from the Railway & Locomotive Historical Society. It has two good articles on the subject.

1) "Risk and the Real Cost of Electrification" by William L Withuhn
2) "Why the Santa Fe Isn't Under Wires" by Wallace W. Abbey

Good writing on why the decision was made not to electrify.

[MichaelSol]

QUOTE: Originally posted by greyhounds

I'd reccomend a back copy of "Railroad History #181" - autumn 1999 from the Railway & Locomotive Historical Society. It has two good articles on the subject.

1) "Risk and the Real Cost of Electrification" by William L Withuhn
2) "Why the Santa Fe Isn't Under Wires" by Wallace W. Abbey

Good writing on why the decision was made not to electrify.

I know one of the gentlemen quite well, and have an immense personal regard for him, but, with all due respect, of these two gentlemen one is an historian and the other a retired public relations executive. and neither has a management or engineering background. Railroad History, while I enjoy the journal, is usually not thought of as a serious journal of engineering analysis. What, exactly, did they discuss?

Best regards, Michael Sol

[MichaelSol]

QUOTE: Originally posted by uzurpator

Wires cost ~1mil/mile. So to electrify you'd need to spend $315 million. That money will cover switching in that yard for several hundread years ;)

Well, 3600 vDC costs about $45,000 per mile to electrify, heavy conductor and all. This $1 mi per mile figure sounds inordinately high.

Best regards, Michael Sol

[Anonymous]

I am still a bit hazzy on the mechanichs of DC electricity. I know DC cannot be stepped up and stepped down like AC can, so how is power in a high voltage transmission line, say 132kv, stepped down to 3000 volts for use in a locomotive? I do know that in many railway applications, when high voltage DC is used, the motors in a 6 motor engine will be connected all 6 in serise, 2 groups of 3 in serise and finally 3 groups of 2 in serise, so the maximum voltage across each motor is never more than 1500 volts. I admire the robustness of high voltage DC applications, but I feel i have to run with the PACK and go for 25kv AC.

[arbfbe]

All of the power fed to the electric locomotives was 3000, 3300 and then 3600 vDC. Speed control was by means of series, series-parallel and parallel connections between the traction motors. Threre were also resistance grids, shunt connections between the motor fields and other things I am only aware of and have no real understanding. Then the MILW wanted to change AC voltages they used transformers and when they wanted to change AC to DC they used an AC motor to run a DC generator to create the voltage they wanted to power the locomotives. Today there are alternatives available for the same purposes but the majority of AC to AC conversions still use transformers.

Modern AC diesels use an alternator to generate AC power. That power is then fed into a set of rectifiers where it is converted into smooth DC current. That DC current is then converted back into AC at the frequency need to give the speed of the locomotive desired. Thus a pure DC feed to the locomotives could be used to power either DC or AC traction motors in one of a new generation of locomotives based on current technology. AC traction motors on electric locomotives used in mountain territory have a number of attractive advantages. Regeneration using the AC traction motors should be much simpler on a DC line since the current would just need to be changed to DC to feed the trolley and would not have to be phase matched to the supply voltages.

[MichaelSol]

QUOTE: Originally posted by jchnhtfd

The AC traction motor is far simpler than a DC traction motor, and has almost overwhelming advantages. If this were not true, there would never be such a thing as AC diesels with their higher price tag. Railroad equipment purchasers and maintenance personnel are not fools...

Unless things have changed, the traction motor was not the high cost maintenance item on diesel-electric locomotives. On our cost per hp maintenance curves for the Milwaukee Road diesel fleet as of 1974, road diesel hp maintenance costs remained fairly constant for approximately the first three years after purchase, then began a steep rise. By the eighth year, the cost per hp of maintenance exceeded the costs of acquisition of new power. This drove purchasing decisions for the diesel-electric fleet. However, the traction motors were not a significant part of that cost, at any point in the curve. The weak spot was not the DC traction motors, the weak spot was the diesel engine.

By comparison, the electric fleet's cost per hp maintenance curves were essentially flat. They were, in nearly all instances, approximately one-third the cost per rated hp of the maintenance of a road diesel-electric at year four, even though the newest units were already a quarter century old, some of the electrics in the fleet were nearly 60 years old and for the period of the study, still in mainline service.

I do not recall traction motor cost or failure being a significant driver of the existing cost of maintaining the electric fleet. An AC motor may be a superior motor to the DC motor, but in economic terms, under most conditions the DC motor delivers the necessary performance without a significant overall maintenance cost difference.

Is it more difficult to maintain? Apparently so.

Is that a significant economic argument in favor of the AC traction motor? If that's all there was to it, sure. But without seeing some current comparable data, the low actual cost of DC traction motors in heavy mainline service, many of them quite old, suggests to me that excepting unusual service demands, there isn't an economic justification for the substantially higher locomotive purchase price, particularly since the design simplicity of the AC motor itself is accompanied by a significant increase in the complexity and cost of the "locomotive" that is able to use the AC motor.

And, the adoption of an AC traction motor does nothing to primary source of increasing maintenance costs: the diesel engine. I guess they've solved a problem that wasn't really a problem, and done nothing for the component that is the cause of 90% of the maintenance costs. This justifies .... what?

The question raised to me is whether the benefits meet or exceed the opportunity cost of the higher cost of acquisition, but also whether or not the more complex machine will ultimately have the same economic service life. A rule of thumb is well tested that more complex machines fail more often than less complex machines. I guess time will tell for the AC diesel-electric and whether that rule has finally been turned on its head.

However, Alan makes a good point. Any characteristic that is genuinely favorable for the AC traction motor is perhaps most efficiently utilized in a DC traction context in order to maximize its economic benefits.

Best regards, Michael Sol