Is re-electrification more complicated than it's worth?

 
  Myrtone Chief Commissioner

Location: North Carlton, Melbourne, Victoria
Let me start by saying I would much like to see re-electrification of both the Melbourne suburban and the Sydney suburban and New South Wales train-link network. But would it be more complicated than it would be worth? Could it be done with little or no disruption to electric trains?

Similar conversion has been done elsewhere in the world, and apparently systems that converted did so a little at a time with dual voltage trains during the transition.

Sponsored advertisement

  neillfarmer Chief Train Controller

The way the national electricity generators and distribution grid is going it might be better to convert the whole lot to diesel.
  Radioman Chief Train Controller

Hello All,

the main High Voltage Transmission in Victoria ( and I presume the rest of Australia ) is 22,00 V AC / 22KvAC , so "off the shelf" 25KvAC equipment could be used without the necessity of boosting the power supply from 22Kv to 25Kv.

And yes, with proper planning and foresight ( and commitment ) it is technically feasible to change over to 22Kv operation. Clearly you need to ensure that a 1500vDC train DOES NOT run onto a 22KvAC line ( or vice versa ) . The SNCF have been doing this for many years, as there is no point in changing over a low voltage DC to high voltage AC if the DC system still has a long life in it.

In the 1950s and 1960s SNCF did extensions to both DC and AC lines before some DC lines went to AC in the late 1970s. I cannot comment on the current status.

Of course, British Railways decided to change over the former xLNER GER 1500vDC Eastern London Suburban over to 6.25/25KvAC from 1959. The DC Project was only 10 years old. The money spent on this conversion would have been better spent on electrifying adjacent lines to 25KvAC. All the 1500vDC trainsets were also converted at great expense , yet the Manchester Sheffield Wrath / MSW remained at 1500vDC , including the former GCR / CLC / LNER Manchester 1500vDC Suburban lines.

When the MSW Project was completed around 1955, proposals to extend the electrification from Wath to Doncaster , the end point for a lot of freight traffic , was not proceeded with due to budgetary reasons, and ultimately the MSW Scheme was closed completely, one wonders if the electrification had been extended to Doncaster if the MSW would have then survived instead of being closed .

Whilst it would have meant mixing two currents on parallel lines , the real aim of the exercise was to ascertain the costs and engineering for the proposed WCML 25KvAC Scheme. ( The 6.25KvAC sections were to accommodate low clearances, though this was later overcome by utilizing a compact Overhead with a lowered track level. ) Change over between 6,25KvAC and 25KvAC was achieved by automatic isolation and change over sections.

Question , although QR, WAGR and Adelaide use 25Kv , is that the actual current or is it 22Kv utilizing 25Kv equipment ?

Best wishes and regards, Radioman.
  Myrtone Chief Commissioner

Location: North Carlton, Melbourne, Victoria
And yes, with proper planning and foresight ( and commitment ) it is technically feasible to change over to 22Kv operation. Clearly you need to ensure that a 1500vDC train DOES NOT run onto a 22KvAC line ( or vice versa ) . The SNCF have been doing this for many years, as there is no point in changing over a low voltage DC to high voltage AC if the DC system still has a long life in it.
Radioman
But S.N.C.F converted to 25 not 22Kv. No further comment on S.N.C.F and not much on the British situation.

Change over between 6,25KvAC and 25KvAC was achieved by automatic isolation and change over sections.
Radioman
And it would be as simple as adjusting the transformer? Apparently all A.C electric locomotives of the time had tap-changers!
  Radioman Chief Train Controller

Dear Myrtone and others,

it is my understanding that 25KvAC is France's ( and Britain's ) transmission voltage, whereas we use 22KvAC. A VR Overhead Engineer in general discussion told me that if we did utilize 22KvAC overhead , we could still buy "off the shelf" 25KvAC equipment as the 3KvAC difference would have no real effect in practice. That being so, I am still curious about the actual voltage used in Qld, SA and WA,

Best wishes and regards, Radioman.
  br30453 Chief Train Controller

Dear Myrtone and others,

it is my understanding that 25KvAC is France's ( and Britain's ) transmission voltage, whereas we use 22KvAC. A VR Overhead Engineer in general discussion told me that if we did utilize 22KvAC overhead , we could still buy "off the shelf" 25KvAC equipment as the 3KvAC difference would have no real effect in practice. That being so, I am still curious about the actual voltage used in Qld, SA and WA,

Best wishes and regards, Radioman.
Radioman
The Queensland, Perth and Adelaide operate on 25,000v AC.

Not sure where you get the 22,000v from.
In Queensland the standards are:

Energex Queensland: We receive electricity from [color=#000000]Powerlink Queensland at bulk supply substations. The electricity is then distributed at 132,000, 110,000 or 33,000 volts to zone substations.[/color]

Zone substations

Zone substations receive electricity through powerlines or underground power cables from the bulk supply substations. They transform this electricity to 11,000 volts for distribution along powerlines or underground cables to distribution substations.
  62440 Chief Commissioner

A study was carried out in the 80's into converting the Blue Mountains to 25kV as the system was not coping with the mix of multiple locos and passenger sparks. It would have had dual voltage trains somewhere beyond Penrith. The conclusion was apparent as the loco fleet was withdrawn and the network became pax only.
  LancedDendrite Chief Commissioner

Location: Gheringhap Loop Autonomous Zone
The main High Voltage Transmission in Victoria ( and I presume the rest of Australia ) is 22,00 V AC / 22KvAC , so "off the shelf" 25KvAC equipment could be used without the necessity of boosting the power supply from 22Kv to 25Kv.
Radioman
A clarification: what we are talking about are 3 different things - a transmission network (1) and a distribution network that is broken down into sub-transmission (2) and distribution ring mains (3).
The high voltage transmission network connects power stations with load centres represented by terminal stations in towns and cities that step down these voltages to supply the distribution network (and in some cases direct connections to very large industrial customers such as aluminium smelters). These networks use voltages of 132kV and higher.
The distribution network is fed by terminal stations and consists of higher voltage point-to-point sub-transmission lines (132kV-22kV) that feed distribution ring mains either at domestic mains voltage (230V single phase or 415V three phase) or at a high/medium voltage (22kV or lower) that is then stepped down to domestic mains voltages closer to the customer.

Regarding this thread topic: In most circumstances railway traction substations (especially new ones) will be fed from the higher voltage parts of sub-transmission network (66kV and higher) and not the distribution ring mains, due to the amount of power that they use. This makes discussion of the use of 22kVAC as a traction supply voltage instead of 25kVAC largely irrelevant, as a voltage step-down is required from 66/33kV to the traction supply voltage anyway. And that's without discussing the use of voltage regulators such as autotransformers and their more modern semiconductor equivalents, which can quite easily affect an average change of 3000V at the same time as they improve the traction power quality...

As for discussion of the many different voltages in the different Australian states:
Victoria (largely) uses a 66kV + 22kV distribution network fed from the 220/330/500kV transmission network. In the Melbourne CBD there are also 11kV and 6kV distribution rings, but that's not relevant to the topic at hand. NSW is 33/22/11kV. SA is 66/33/11kV.
  justapassenger Minister for Railways

the main High Voltage Transmission in Victoria ( and I presume the rest of Australia ) is 22,00 V AC / 22KvAC , so "off the shelf" 25KvAC equipment could be used without the necessity of boosting the power supply from 22Kv to 25Kv.
Radioman
Neither ElectraNet SA (transmission) or SA Power Networks (distribution) operate any 22kV AC lines in SA.

22kV would be the medium voltage (regional) distribution lines, not the high voltage (long distance) transmission lines.

Question , although QR, WAGR and Adelaide use 25Kv , is that the actual current or is it 22Kv utilizing 25Kv equipment ?
Radioman
The current and future substations for the Adelaide rail electrification supply take a 66kV AC feed from the SA Power Networks distribution network and step it down to 25kV AC for the rail traction supply.
  mikesyd Chief Commissioner

Location: Lurking
What benefits are there for the Passengers if the wires above carry a different voltage?

After they have endured the massive bustitutions while the changes are being made of course.
  billjohnston Station Master

None for the passengers but significant cost reductions when extensions are carried out. I think there are at least two substations required for the Mernda extension and about 10 for a Geelong extension. None would be required for the Mernda extension if it was 25kV AC. These costs tend to mitigate against extensions.
There is also significant remedial costs to underground services caused by corrosion due to stray DC currents. These would also be mitigated with AC. If there was at least a policy of ultimate conversion to AC then all the new overhead work being done now and all the work done in the late 80's could be done with 25kV AC insulation in mind.  The current work to upgrade numerous DC substations could all be avoided as the Vic system would only require a handful of new AC substations and the enormous heavy DC conductor work on the Dandenong long would have been avoided.

Bill Johnston
  justapassenger Minister for Railways

What benefits are there for the Passengers if the wires above carry a different voltage?
mikesyd
At some point the infrastructure will need to be replaced, may as well convert to the 25kV system at that point to get the benefits of the higher capacity and lower voltage drop.

The higher capacity will allow trains to run without restrictions on power usage, and allow for more electric services to be run.  This would allow regional services to be swapped over to bi-mode stock which would run from the wires in the metro areas (beneficial for local residents as well as passengers) and switch to diesel power for the regional areas yet to be electrified.

Switching to AC electrification additionally eliminates the electrolysis problem, resulting in fewer closures for maintenance.

After they have endured the massive bustitutions while the changes are being made of course.
mikesyd
There's no need for massive bustitutions if you have a competent project manager in charge of delivering it.

Simply use bi-mode rolling stock (which could later be cascaded to regional routes once the electrification renewal is complete) or a DMU shuttle service across the 'gap' and get the work done at nights and weekends.
  kitchgp Chief Commissioner

Not in any way an argument against AC, but is there an increased risk for train surfers with AC as opposed to DC?
  justapassenger Minister for Railways

No, unless they have a pacemaker.
  kitchgp Chief Commissioner

Thanks. I'll cancel my order for a 50mm wetsuit.
  gordon_s1942 Chief Commissioner

Location: Central Tablelands of NSW
The rule between AC and DC is that DC will burn you but AC paralyses you which is why its more dangerous than DC.

AC will jump across a gap easier than DC, you only have to look at how a spark plug fires.
Also this danger was extensively demonstrated by Thomas Edison during the AC/DC War he had with Nicolas Tesla.

AC travels further with far less loss than DC, look at any electrified railway using DC to see the catenary is made of quite substantial Copper wire and you need substations every 10/15 kilometres to feed it but the line carrying the high voltage (15,000~30,000) AC that feeds the substation is far smaller.
  Mufreight Train Controller

Location: North Ipswich
To convert a DC electrification to AC the first works would be to replace the insulators supporting the overhead and the supply, this can all be done while still operating on DC. then the next step is the immunisation for the signalling, then with all that done it becomes a simple exercise to on a given day change over the supply and go to AC electrification, trains could continue to operate on the DC supply up until that time, it would seem that the change overs to some systems have been handled that way overseas with the final change overs being done in a matter of days so no big deal if there are sufficient staff avaliable.
  Myrtone Chief Commissioner

Location: North Carlton, Melbourne, Victoria
A clarification: what we are talking about are 3 different things - a transmission network (1) and a distribution network that is broken down into sub-transmission (2) and distribution ring mains (3).
The high voltage transmission network connects power stations with load centres represented by terminal stations in towns and cities that step down these voltages to supply the distribution network (and in some cases direct connections to very large industrial customers such as aluminium smelters). These networks use voltages of 132kV and higher.
The distribution network is fed by terminal stations and consists of higher voltage point-to-point sub-transmission lines (132kV-22kV) that feed distribution ring mains either at domestic mains voltage (230V single phase or 415V three phase) or at a high/medium voltage (22kV or lower) that is then stepped down to domestic mains voltages closer to the customer.
LancedDendrite
Well actually, even the domestic standard is actually three-phase, 240v being the line to ground Root Mean Squared (R.M.S - the peak voltage being higher), but each phase goes to every third residence.

Regarding this thread topic: In most circumstances railway traction substations (especially new ones) will be fed from the higher voltage parts of sub-transmission network (66kV and higher) and not the distribution ring mains, due to the amount of power that they use. This makes discussion of the use of 22kVAC as a traction supply voltage instead of 25kVAC largely irrelevant, as a voltage step-down is required from 66/33kV to the traction supply voltage anyway. And that's without discussing the use of voltage regulators such as autotransformers and their more modern semiconductor equivalents, which can quite easily affect an average change of 3000V at the same time as they improve the traction power quality...
LancedDendrite
Another issue here is how to distribute the phases of the three phase supply. Single wire overhead is limited to one phase. One way to go about it is to feed each of three phases to three different sections of the electrified network. The larger the network, the bigger the area that can be continuously powered by a single phase.
Another idea is to convert the three-phase to two-phase, such as with a Scott-connected transformer. While an unbalanced load on one side causes an unbalanced current on the other, I believe that that it may be easier to balance the instantaneous load on a two-phase supply than on a three-phase supply.
  LancedDendrite Chief Commissioner

Location: Gheringhap Loop Autonomous Zone
  woodford Chief Commissioner

LancedDendrite
While for those of us that have been on a forum/mailing list for a considerable period of time repeated questions can be something of a pain, if someone asks a question its just good manners to answer it. Particularly when searching Railpage for a the exact bit of information one requires from my experince is an experience of extreme frustration.

woodford
  woodford Chief Commissioner

THe major benefit of electrifaction of a line is the ability of passenger trains to accelerate to speeds above 130kph in short period of time as it allows traction systems of VERY high powers. Electric locomtives of 11,000bhp being quite common in Europe, powers quite impossible in a diesel powered locomotives.

woodford
  Myrtone Chief Commissioner

Location: North Carlton, Melbourne, Victoria
AC will jump across a gap easier than DC, you only have to look at how a spark plug fires.
Also this danger was extensively demonstrated by Thomas Edison during the AC/DC War he had with Nicolas Tesla.
gordon_s1942
Yes, A.C can go across inductive and capacitive coupling. Also, spark plugs use pulsed D.C, not A.C. Higher voltages can jump across larger spark gaps.

AC travels further with far less loss than DC, look at any electrified railway using DC to see the catenary is made of quite substantial Copper wire and you need substations every 10/15 kilometres to feed it but the line carrying the high voltage (15,000~30,000) AC that feeds the substation is far smaller.
gordon_s1942
Higher voltages travel further with less loss, and electrified railways using A.C use higher voltages than any one using D.C. In fact, D.C travels further with less loss than the same number of volts A.C. A.C is subject to capacitive and dielectric losses and something called the skin effect occurs only on A.C, not D.C.
  simstrain Chief Commissioner

Let me start by saying I would much like to see re-electrification of both the Melbourne suburban and the Sydney suburban and New South Wales train-link network. But would it be more complicated than it would be worth. Could it be done with little or no disruption to electric trains?

Similar conversion has been done elsewhere in the world, and apparently systems that converted did so a little at a time with dual voltage trains during the transition.
Myrtone
Not sure what you getting on in regards to re electrification of the nsw train link network. The wires go a decent distance up here and the regional network has never been electrified.
  tazzer96 Deputy Commissioner

Its alot more complicated than you think, unless it was built for conversion later, then its not going to be cheap.  All of the insulation is designed for 1500v DV, not 25kv AC.  Its not a case of just changing the substations.

Sponsored advertisement

Subscribers: Boss 2, br30453, Myrtone, Radioman

Display from:   

Quick Reply

We've disabled Quick Reply for this thread as it was last updated more than six months ago.