1500V DC

[Richard Scott]

Was interested in capabilities of the 1500Volt Direct Current system. What is the maximum current through the wires? Taking a French 7200 as an example I believe it's rated at 4400kW meaning it would draw a current of around 3000A at maximum power and maybe more if train supply on? Would've thought the wires were getting quite warm at this stage especially if 2 locos are in multiple or other trains in same section?
Notice locos often depart stations with both pantographs up, one dropping after a short while; is this due to high starting currents?

 

[MarkyT]

Was interested in capabilities of the 1500Volt Direct Current system. What is the maximum current through the wires? Taking a French 7200 as an example I believe it's rated at 4400kW meaning it would draw a current of around 3000A at maximum power and maybe more if train supply on? Would've thought the wires were getting quite warm at this stage especially if 2 locos are in multiple or other trains in same section?

I know the copper overhead contact wire and catenary is significantly bigger and heavier than that used for 25kV which has implications for size and cost of supporting structures. I would have thought substation spacing is fairly similar to that employed on 3rd rail DC. Rather than heat, the main problem with all that current is voltage drop through the loop resistance of the supply line and return rail, which without frequent substation feed in sites would limit the power available to traction at extremities of supply. The power loss manifests as heat generated though.

Notice locos often depart stations with both pantographs up, one dropping after a short while; is this due to high starting currents?

Probably helps to distribute the very high starting current between a number of pantographs to reduce resistance and limit any damage to the contact surfaces through arcing.

 

[Richard Scott]

I know the copper overhead contact wire and catenary is significantly bigger and heavier than that used for 25kV which has implications for size and cost of supporting structures. I would have thought substation spacing is fairly similar to that employed on 3rd rail DC. Rather than heat, the main problem with all that current is voltage drop through the loop resistance of the supply line and return rail, which without frequent substation feed in sites would limit the power available to traction at extremities of supply. The power loss manifests as heat generated though.

Probably helps to distribute the very high starting current between a number of pantographs to reduce resistance and limit any damage to the contact surfaces through arcing.

Thanks for info - had noticed wire looks significantly thicker than 25kV contact wire; have also noticed it's twin wires on occasions and also seen this on 3000VDC, guessing again it's in areas where current demand is higher e.g. starting away from station stops.

 

[AlexNL]

Here in the Netherlands, the max. available amperage is 4000A. Substations are placed 7 km apart on average.

 

[axlecounter]

In Italy (3kV!) double wire is a standard and in some areas triple wire is used!

 

[MisterT]

Notice locos often depart stations with both pantographs up, one dropping after a short while; is this due to high starting currents?

It was, for the older trains, but with the modern equipment, the starting current is not the culprit anymore. That honour goes to the HVAC systems, which is why you won't/shouldn't see it on short trains or on freight trains (and when you see it on those trains, it has either an old locomotive at the front, or the driver doesn't understand what he/she is doing ).

 

[SHD]

It was, for the older trains, but with the modern equipment, the starting current is not the culprit anymore. That honour goes to the HVAC systems, which is why you won't/shouldn't see it on short trains or on freight trains (and when you see it on those trains, it has either an old locomotive at the front, or the driver doesn't understand what he/she is doing ).

Not that the electricity consumption for auxiliaries and train heating power when stationary was certainly also a reason to raise both pantographs in the days of resistor-controlled locomotives. With typical European LHCS (800 A train heating powerline under 1.5 kV), the "idle" current draw can seriously endanger the catenary with several hundred amps going through a single point for a prolonged period of time.

Note also (and I will be very pedantic) that certain freight trains need an energised power line (e.g. refrigerated wagons)!

 

[MisterT]

The use of the second pantograph was of course partly for the heating too. 800A is just a maximum, not the usual power draw. I have never seen 800A in my years as a driver, just a few hundred A, max. And that was with 16 sleeper coaches attached (the now no longer existing CityNightLine or EuroNight trains).
With 9 or 10 coaches, in regular (Dutch) weather, the power draw is around 50, maybe 100A, so nothing special. With our current Traxx locomotives, we even get a warning as soon as the power draw exceeds 300A. Even with very cold or hot weather, we never get to that point.

Refrigerated wagons are not used in the Netherlands, or not anymore. We now simply bring the car trailers or containers on board on flat wagons. The refrigerated trailers/containers all have their own (small) refrigerators attached. So no, to my knowledge, there aren't any freight trains that use the power line.

But of course, all above is my own experience. I have no knowledge about other countries.

 

[Ash Bridge]

Thanks for info - had noticed wire looks significantly thicker than 25kV contact wire.

This used to be very apparent on the the approaches to Manchester Piccadilly from Ardwick Junction where the 1500V DC Catenary of the Woodhead Route joined and ran alongside the 25KV AC of the WC Mainline for a couple of km or so.

 

[SHD]

Was interested in capabilities of the 1500Volt Direct Current system. What is the maximum current through the wires? Taking a French 7200 as an example I believe it's rated at 4400kW meaning it would draw a current of around 3000A at maximum power and maybe more if train supply on? Would've thought the wires were getting quite warm at this stage especially if 2 locos are in multiple or other trains in same section?
Notice locos often depart stations with both pantographs up, one dropping after a short while; is this due to high starting currents?

The most powerful 1.5 kV locomotive ever was the French CC6500, rated at 5,900 kW - continuous power. (*) I think it also held the record for the most powerful DC locomotive ever (**) as I am not aware of a more powerful classic 3kV locomotive in either Belgium (Series 20 - 5,200 kW) or Italy (FS E.656 - 4,800 kW).

(*) I am talking here about classical DC locomotives, not counting recent multisystem locomotives. However even the SNCB Class 18 is rated at 5,000 kW continuous power under 3 kV DC. Only PKP's EU44 (6,000 kW) and Skoda's E109 (6,400 kW) have higher ratings.
(**) not counting incredible Soviet/Russian double locomotives such as the historical ВЛ15/VL15 or current 2ЭС10/2ES10 (8,400 kW)

CC6500s had two motors, each electrically divided into two "half-engines" - actually, the inductor and armature were designed with two separate sections. The maximal permissible current was 1,400 A per half-engine. In standard circumstances, a train could be started under the series-parallel coupling. At locations with a single-wire 1500 V OHL, it was mandatory to start the train under the series coupling, with IIRC an intensity limit of 1,200 A. Even with two pants up, this meant 600 A per pantograph (not counting auxiliary power).

But of course, all above is my own experience. I have no knowledge about other countries.

There are not many countries that have 1.5 kV mainline electrification

 

[MarcVD]

A typical DC catenary on the main line will have 4 wires : a main and auxiliary "holder" which are usually made of wired bronze and two contact wires made of solide pure copper. Belgian catenary has an equivalent total section of 400 mm2 of copper. French one, with only 1500V instead of 3000, has 600. A high voltage AC catenary usually has less than 150, more dictated by mechanical strenght than electrical resistance. Belgian railways now deploy a new catenary system, suitable for higher speeds, with only 3 wires, but with a parallel feeder câble.

 

[43096]

(*) I am talking here about classical DC locomotives, not counting recent multisystem locomotives. However even the SNCB Class 18 is rated at 5,000 kW continuous power and under 3 kV DC. Only PKP's EU44 (6,000 kW) and Skoda's E109 (6,400 kW) have higher ratings.

The PKP EU44 is not alone as it is only an ES64U4 variant, so this also applies to Austrian 1216, Italian E190, Slovenian 541 etc. Indeed as the ES64U4 is essentially the internals from the ES64F4 (German 189) inside a modified Taurus bodyshell and mechanicals, this also applies to the ES64F4. Siemens quote them as rated at 4.2MW under 1.5kV DC catenary and 6.0MW under 3kV DC.

 

[jopsuk]

There are not many countries that have 1.5 kV mainline electrification

Depends a little on your definition of "mainline" though

 

[SHD]

Well, as in WCML or ECML... indeed this list illustrates what I meant to convey: beyond the many metros, commuter rail, and rural networks that use 1.5 kV, two countries stand out where 1.5 kV electrification has been carried out since the 1920s on mainlines with a mix of local and long-distance, slow and fast, freight and passenger traffic, with speeds up to 200 and even 220 km/h.

 

[Groningen]

Words is in the Netherlands that only a certain amount of trains can depart at the same time otherwise the Voltage would drop. Maximum speed is 160 kilometers an hour.

 

[anme]

Is there ever discussion of converting 1500 or 3000V DC lines to 25kV AC (or similar)? I appreciate this would be a big undertaking, but could it be worthwhile if done, for example, when electrical infrastructure was renewed?

 

[edwin_m]

Is there ever discussion of converting 1500 or 3000V DC lines to 25kV AC (or similar)? I appreciate this would be a big undertaking, but could it be worthwhile if done, for example, when electrical infrastructure was renewed?

We did of course do this with relatively new infrastructure on the Great Eastern when it was decided to standardise on 25kV (and at the time 6.25kV in urban areas). Much later the Hadfield line was similarly converted. Several countries with DC have adopted 25kV for high speed or other new electrification schemes (France, Spain, Italy, Russia), but I can't think of any major conversions outside the UK - our local correspondents may know better! I seem to recall the Netherlands and Latvia are considering conversion.

 

[etr221]

Is there ever discussion of converting 1500 or 3000V DC lines to 25kV AC (or similar)? I appreciate this would be a big undertaking, but could it be worthwhile if done, for example, when electrical infrastructure was renewed?

We did of course do this with relatively new infrastructure on the Great Eastern when it was decided to standardise on 25kV (and at the time 6.25kV in urban areas). Much later the Hadfield line was similarly converted. Several countries with DC have adopted 25kV for high speed or other new electrification schemes (France, Spain, Italy, Russia), but I can't think of any major conversions outside the UK - our local correspondents may know better! I seem to recall the Netherlands and Latvia are considering conversion.

The GE from Liverpool St to Southend Vic. was converted from 1500v dc to 6.25kV over a weekend (dc service on Friday, ac trains running by Sunday evening) - that was more or less a case of changing the substation connections, without any change to the overhead wiring - this did happen much later, when the voltage was changed to 25kV. On to Chelmsford, and the later Manchester area conversions (to Altrincham and Glossop/Hadfield) were direct to 25kV, and did involve wiring alterations, and took longer.

Parts of the Soviet/Russian system have been converted (one notable stretch was the Trans-Siberian either side of Irkutsk, which had been a relatively early isolated dc scheme), to eliminate dc 'islands' in otherwise ac areas.

The other country with an extensive 1500v dc electrified network is Japan (see https://en.wikipedia.org/wiki/Railway_electrification_in_Japan and https://upload.wikimedia.org/wikipe...ay_Electrification_Systems_Map_日本本線鉄道電化地図.png).

The initially suburban networks in/around Bombay/Mumbai and Sydney were later extended (Bombay quite early, in the 1920s) as mainline systems for all traffic (although the Australians have now given up on electric loco haulage of freight), and, in their day, were quite significant.
I understand (looking at Wikipedia) that the Mumbai (Bombay) area has now all been converted to 25kV ac; as was earlier the initial 3000v dc electrification out of Howrah (Calcutta/Kolkata), and the pre-war 1500v dc electrification in the Madras/Chennai area.

 

[Groningen]

There was word that the Netherlands could get a new voltage. There is room in the 86, 87, 94 and 95 class, but nothing happens.

 

[MarcVD]

Is there ever discussion of converting 1500 or 3000V DC lines to 25kV AC (or similar)? I appreciate this would be a big undertaking, but could it be worthwhile if done, for example, when electrical infrastructure was renewed?

Luxembourg just finished converting its sole 3 kV line to the belgian border at Kleinbettingen to 25 kV 50 Hz. SNCB is busy renewing and converting the whole line from Namur to Arlon and the Lux border from 3 kV to 25 kV.

 

[delticdave]

There was word that the Netherlands could get a new voltage. There is room in the 86, 87, 94 and 95 class, but nothing happens.

I've seen video of the new line from Lelystad to Zwolle & that seems to be built for a possible change to 25 kV AC, (bigger insulators, & a separate power feed for split-phase 50 kV AC) but the heavy catenary make's it obvious that it's still fed with 1.5 kV DC.

 

[MisterT]

The change to 25 kV was considered years ago, and new projects were build in preparation for that, but it turned out that the project would cost too much money.
Now the proposition is to change from 1500V to 3000V, in line with Belgium and now it's up to the government to green-lit it.

 

[delticdave]

The change to 25 kV was considered years ago, and new projects were build in preparation for that, but it turned out that the project would cost too much money.
Now the proposition is to change from 1500V to 3000V, in line with Belgium and now it's up to the government to green-lit it.

Interesting, is doubling the voltage cost-effective? As in, how easy to modify rolling stock, infrastructure & sub-stations?
I suspect the load on the power grid wouldn't change but some of the older stock would require serious modifications.

 

[SHD]

We did of course do this with relatively new infrastructure on the Great Eastern when it was decided to standardise on 25kV (and at the time 6.25kV in urban areas). Much later the Hadfield line was similarly converted. Several countries with DC have adopted 25kV for high speed or other new electrification schemes (France, Spain, Italy, Russia), but I can't think of any major conversions outside the UK - our local correspondents may know better! I seem to recall the Netherlands and Latvia are considering conversion.

The Bellegarde-Geneva section of the Lyon-Geneva line, electrified at 1.5 kV DC in 1956 (and equipped with French BAL block signalling), was reelectrified at 25 kV in 2014, although the Lyon-Bellegarde section remains electrified at 1.5 kV DC. There were several reasons, both on the Swiss and French side, to push for 25 kV electrification:

- the creation of Geneva's transborder "RER" (commuter rail network), which was planned to run on 25 kV electrified lines in France and thus would have required complex tri-voltage rolling stock (1.5 kV DC / 15 kV 16.7 Hz / 25 kV 50 Hz AC)
- the reopening of the Haut-Bugey line in France (as I already said here, one of the most scenic lines in France), electrified at 25 kV until Bellegarde, for Paris-Geneva TGVs.

The conversion of the Chartres-Le Mans section to 25 kV was considered before construction of the TGV Atlantique was decided. Chartres-Le Mans was electrified at 1.5 kV in 1937 as part of the Paris Montparnasse - Le Mans electrification. The 1.5 kV substations were quite weak on this section, and did not always deliver the power needed for the heavy peak traffic (notably at weekends); voltages of barely 1,100 V were not uncommon (the main breaker of SNCF DC locomotives and EMUs opens if the voltage drops below 1,100 V or exceeds 1,800 V). The opening of the TGV Atlantique has freed the classic Paris-Le Mans line of its long-distance mainline traffic and the re-electrification became unnecessary.

 

[AM9]

Interesting, is doubling the voltage cost-effective? As in, how easy to modify rolling stock, infrastructure & sub-stations?
I suspect the load on the power grid wouldn't change but some of the older stock would require serious modifications.

Actually the mods from 1500VDC to 3kVDC can be quite simple. Many 1500V designs already have motors wired in series pairs. Extending that to two series pairs and rearranging the switchgear to do the series parallel changeover with pairs rather than single motors saves much of the power that's lost in the resistor banks. On modern designs that have electronic current control, it would probably be cheaper to replace them with higher voltage types.
The overall load on the feed would go down slightly as there would be less resitive losses in the OLE, but the power delivered to the motors would be the same.

 

[edwin_m]

Going from 1500V to 3000V would halve the current required to provide the same power, so would reduce resistance losses by 75% (give or take various minor adjustments) because the losses are proportional to the square of the current. If the trains have regenerative braking then the proportion of power it recovers should increase too. Alternatively the benefit could be taken as more widely-spaced feeder stations or more power available to the trains.

However if you're going to the trouble of converting then, except in a special case such as this one that already links to a 3000V line, you might as well go to 25kV where the benefits are much larger.

 

[SHD]

Taking a French 7200 as an example I believe it's rated at 4400kW meaning it would draw a current of around 3000A at maximum power and maybe more if train supply on? Would've thought the wires were getting quite warm at this stage especially if 2 locos are in multiple or other trains in same section?

The raise in temperature of the OHL may indeed be significant. On the Chartres-Le Mans section mentioned above, it was even used to defrost the catenary in certain weather conditions, by powering only the section of catenary downstream of the running train.

TGVs are de-rated under 1.5 kV with power capped at 3,680 kW (3,100 for PSE trainsets) which nevertheless represents a hefty 7,360 kW for a multiple unit of two trainsets. Until the opening of the LGV Sud Europe Atlantique, they could use that kind of power on the 220 km/h sections of the Tours-Bordeaux line (add a few hundred kW for train auxiliaries, especially in summer).

FWIW BB 7200s are rated at 4,040 kW. Their Dutch cousins are indeed rated at 4,400 kW.

 

[Richard Scott]

Thanks for correction on power output of 7200s, took the info from Dutch locos assuming (wrongly) that they were the same. Probably listening to them would tell me they aren't!
Another query I'm guessing there's no neutral sections as in AC supplies so just boosted by substations every so often (and presuming that this is the same for our 750V third rail system)?

 

[SHD]

Thanks for correction on power output of 7200s, took the info from Dutch locos assuming (wrongly) that they were the same. Probably listening to them would tell me they aren't!
Another query I'm guessing there's no neutral sections as in AC supplies so just boosted by substations every so often (and presuming that this is the same for our 750V third rail system)?

Sorry, I need to correct my correction, BB7200s - as well as BB15000s and BB22200s - are indeed rated at 4.4 MW (4,420 kW to be precise) and they have the same TAB674 motors as their French and Dutch cousins. That’ll teach me to rely on Wikipedia for a quick check.

Speaking about third rail, the Maurienne valley line was electrified at 1,500 V in the 1930s with third rail. Trains were hauled up the 30‰ gradients by these monsters (later known as 2CC2 3400):



The third rail was replaced by an OHL in the 1970s. A small sub-series of CC6500s (painted dark green) had been fitted with shoes for operation on this line.

In addition, the early electrification of commuter lines in Paris was carried out at 750 V DC third rail, starting in the early 1900s. This electrification system was gradually replaced/phased out - by 1,500 V DC on the Austerlitz (1920s/30s) and Invalides (1970s) lines and by 25 kV AC on the Saint-Lazare lines (1960s/1970s), except the Nanterre - Saint Germain en Laye section that was transferred to RATP’s RER and electrified at 1,500 V. The last 3rd rail trains ran in 1985 on the Ligne d’Auteuil (don’t look for it under this name, it has been remodeled, electrified at 1.5 kV and integrated to RER C) and 1993 on the Ligne des Moulineaux (transformed into a very successful tram).

 

[Cricketer8for9]

There is something truly impressive about early electric locos. No attempt to make them look pretty, just functional boxes, but such big boxes.