My Ideas for 3rd Rail Expansion

[gooding36@gmai]

I would like to see a bigger programmed of OLU and 3rd rail for us in the south-west of England,
complete the OLU of the Reading to Taunton Line and possibly extend it to Exeter and up to Bristol.
Where i live i would like to see the extension of 3rd rail from Basingstoke to Yeovil Junction.

 

[Railwaysceptic]

Welcome to this forum.

I'm afraid I have some bad news for you. The ORR's interpretation of current health and safety rules about electricity in workplaces prevents authorisation of any new third rail electrification, so no-one at present will contemplate extending third rail from Basingstoke to anywhere.

 

[GRALISTAIR]

Welcome to the forum. There is a slight possibility that 3rd rail infill in certain places in the South EAST of the country might happen but southwest no way. It will be 25kV AC OHLE for that area of the country.

 

[anthony263]

Yet I heard and read elsewhere that the orr are softening on their position regarding 3rd rail so some extensions might be happen

 

[Lewlew]

Yet I heard and read elsewhere that the orr are softening on their position regarding 3rd rail so some extensions might be happen

Think it's more "logical infilling" rather than extensions

 

[Railwaysceptic]

Yet I heard and read elsewhere that the orr are softening on their position regarding 3rd rail so some extensions might be happen

Where did you hear/read that?

 

[D365]

Think it's more "logical infilling" rather than extensions

Agreed. Third rail makes sense for metro and metro-esque systems (think Merseyrail), but I would be shocked if any mainline third rail electrification was to be authorised, let alone considered.

 

[London Trains]

Really there is no chance any more third rail extensions, but if it were up to me, I would third rail electrify Hurst Green to Uckfield and Ore to Ashford, because they are small diesel islands in massive third rail areas. For Merseyrail I would extend it with OHLE.

 

[davetheguard]

Where did you hear/read that?

The latest edition of Modern Railways magazine makes some mention of the ORR position on third rail softening. Obviously only anthony263 will know what his source was.

 

[RichJF]

The only & I mean only third rail building you'll likely see (if ever) will be Hurst Green - Uckfield & Ore - Hastings. Even then it's unlikely as I wouldn't be surprised to see a 3rd rail bi-mode EMU than can be coupled with the Electrostars in the South already.

My hunch is that 25kv OLE will replace 3rd rail on major routes before any new 3rd rail stuff is authorised.

 

[DBNR]

Apart from the safety issue referenced above, what is the objection to the use of 3rd rail to expand / electrify where aesthetics may be an issue?

 

[Domh245]

Apart from the safety issue referenced above, what is the objection to the use of 3rd rail to expand / electrify where aesthetics may be an issue?

The blocker is entirely safety grounds. (lack of) visual impact doesn't come into it at all because they can't build it in the first place (although this is subjective as you need more frequent substations to feed it). If however you could put it down to lessen visual impact, speed could be a limiting factor (100mph maximum for third rail) as well as complicating the rolling stock

 

[swt_passenger]

The blocker is entirely safety grounds. (lack of) visual impact doesn't come into it at all because they can't build it in the first place (although this is subjective as you need more frequent substations to feed it). If however you could put it down to lessen visual impact, speed could be a limiting factor (100mph maximum for third rail) as well as complicating the rolling stock

It’s also electrically very inefficient, losses due to the much higher current flowing are significantly greater than 25 kV...

 

[alistairlees]

The only & I mean only third rail building you'll likely see (if ever) will be Hurst Green - Uckfield & Ore - Hastings. Even then it's unlikely as I wouldn't be surprised to see a 3rd rail bi-mode EMU than can be coupled with the Electrostars in the South already.

My hunch is that 25kv OLE will replace 3rd rail on major routes before any new 3rd rail stuff is authorised.

I think you mean Ore to Ashford. Ore to Hastings has been electrified since the 1980s.

 

[alistairlees]

It’s also electrically very inefficient, losses due to the much higher current flowing are significantly greater than 25 kV...

I would be interested to know how much less efficient. Any idea?

 

[yorksrob]

I think you mean Ore to Ashford. Ore to Hastings has been electrified since the 1980s.

Since 1935 infact !

 

[swt_passenger]

I would be interested to know how much less efficient. Any idea?

I’d be guessing, I’m afraid. But someone’s definitely come up with figures in a previous thread...

 

[Railwaysceptic]

The latest edition of Modern Railways magazine makes some mention of the ORR position on third rail softening. Obviously only anthony263 will know what his source was.

Thank you for that. Now that people are abandoning Lockdown and shops are re-opening, I might be able to buy a copy of Modern Railways. In fact, I may take out a subscription to future-proof myself against the effects of any second Lockdown.

 

[anthony263]

Thank you for that. Now that people are abandoning Lockdown and shops are re-opening, I might be able to buy a copy of Modern Railways. In fact, I may take out a subscription to future-proof myself against the effects of any second Lockdown.

Yes it was in modern railways I read it. Sorry for late reply having a young child I dont get much time to go online on my days off.

As for a 2nd lockdown I can see it happening in england soon enough

 

[GRALISTAIR]

It’s also electrically very inefficient, losses due to the much higher current flowing are significantly greater than 25 kV...

I would be interested to know how much less efficient. Any idea?

I will try and dig out the thread for you - it is posted in the pinned thread on electrification resources. To deliver power it is Amps x volts. 25000 volts AC (in theory more on AT) vs 750 volts DC means you have to have a huge amount more current for the same power.


Electrically power loss is equal to the current squared multiplied by the resistance. So that is a lot. I have posted a calculation on this board before and as I said I will try and dig it out.

 

[Whistler40145]

Isn’t 3rd Rail far more expensive a system to maintain and not as reliable as 25kV OHLE?

 

[83A]

but I would be shocked if any mainline third rail electrification was to be authorised,

Thats why they are banning it.......badum !!!

 

[GRALISTAIR]

I would be interested to know how much less efficient. Any idea?

I’d be guessing, I’m afraid. But someone’s definitely come up with figures in a previous thread...

Assume 2500 kW required = 2500000 watts
AC 25000 volts = 2500000/25000 = 100 amps current
DC 750 volts = 2500000/750 = 3300 amps
Assume 1 ohm resistance (ignore difference copper/carbon contact wire or steel pick up rail)
Power loss = I2R = 100 x 100 x 1 = 10000 watts
= 3300 x 3300 x 1 = 10890000 watts

very rough simplistic calculation

 

[83A]

I will try and dig out the thread for you - it is posted in the pinned thread on electrification resources. To deliver power it is Amps x volts. 25000 volts AC (in theory more on AT) vs 750 volts DC means you have to have a huge amount more current for the same power.


Electrically power loss is equal to the current squared multiplied by the resistance. So that is a lot. I have posted a calculation on this board before and as I said I will try and dig it out.

Yes

If we took say a 4MW loco @ 25KV that’s 160A current

4MW @ 750V = 5333A

So a much higher current draw on 3rd rail, the issue with current it generates heat, which wastes energy.

Hence why the national grid uses 250KV for the main power distribution network.

Note: I am not an expert on OHL but I think in some locations they use 50KV and the auto transform to 25KV for the contact wire. Hence reducing further the current.

 

[GRALISTAIR]

Hence why the national grid uses 250KV for the main power distribution network.

400kV in a lot of places too.

 

[Bald Rick]

Isn’t 3rd Rail far more expensive a system to maintain and not as reliable as 25kV OHLE?

Maintenance is about the same for the third rail itself, but it imposes a lot of extra cost on track maintenance.

Reliability - railways that have third rail are typically less reliable than those with OLE, but more reliable than diesel.

 

[Whistler40145]

The 3rd rail system requires substations at far more frequent distances than 25kV, especially with the Autotransformer system

 

[AM9]

I’d be guessing, I’m afraid. But someone’s definitely come up with figures in a previous thread...

I think that Bald Rick has posted the order of efficiencies of both systems in the past. As I recall it, OLE at 25kV has a total power loss of about 5-10%, whereas 3rd rail 750VDC can lose about double that, (10-20%). The comparison is really route, speed, traffic density and likely climate dependent, as it impacts on the degree of mitigations required, - especially for 3rd rail.

 

[Bald Rick]

I think that Bald Rick has posted the order of efficiencies of both systems in the past. As I recall it, OLE at 25kV has a total power loss of about 5-10%, whereas 3rd rail 750VDC can lose about double that, (10-20%). The comparison is really route, speed, traffic density and likely climate dependent, as it impacts on the degree of mitigations required, - especially for 3rd rail.

Not me, I left my electrical knowledge that needs formula behind me 3 decades ago!

 

[AM9]

OK, - sorry that I presumed you were still involved in such lowly matters.
Edit: to prevent any misunderstanding of the above, there should have been one of these at the end of the line:

In retrospect, it may have been a sadly no longer active member of RUK, - philip phlopp