Electrified Lines

[mike1990]

Are they a good thing? To me they just seem like another thing that can go wrong as was the case recently in London. Maybe I'm missing the advantages...

 

[NSE]

Yeah I'd say they are a good thing. Better for the environment to have an electric train than a diesel chucking out fumes, but then one diesel train could take maybe 100 cars off the road, so it still works out better I guess. Like you say though more to go wrong, trees bringing down cables etc. Also I believe electric trains are quicker at accelerating so a plus for commuter runs.

I guess it's pro's and con's really.

 

[OxtedL]

Living on a line which sees both, electric trains accelerate faster, make less noise, and generally are nicer. Maybe things can go wrong more, but then again perhaps not. Southern are far more likely to cancel a diesel Uckfield train than an electric East Grinstead train due to train failure, in my experience.

PS (can you respell the thread title please?)

 

[SS4]

I would say yes largely for the environmental benefits. Remember that in a diesel you also have to carry the fuel you're going to burn.

Electrical failures are very uncommon, it's just when they are they make the news - when was the last time there was an electrical failure on your local electrical line?

Also of course the media do not understand that Great Britain extends beyond zone 2/the M25

 

[trentside]

I think the environmental factor is a major catalyst for further electrification schemes, such as the GWML and North West. This obviously throws up the debate about where the extra electricity will come from (i.e. how will it be generated? Is it sustainable? etc). Still, as NSE says, a single train can take hundreds of cars off the road!

I actually think electrification is a good thing - the trains are quieter and better for stop start commuter services than diesel traction!

 

[SS4]

I think the environmental factor is a major catalyst for further electrification schemes, such as the GWML and North West. This obviously throws up the debate about where the extra electricity will come from (i.e. how will it be generated? Is it sustainable? etc). Still, as NSE says, a single train can take hundreds of cars off the road!

I actually think electrification is a good thing - the trains are quieter and better for stop start commuter services than diesel traction, as I understand it.

Agreed although current loss at high voltage is relatively low (especially 25kV AC as in overhead lines) and of course it's infinitely easier to make a power plant clean than a train. When we factor in the fact that electric motors are very efficient the transmission losses are more than offset

 

[sprinterguy]

Electric trains are quieter, cleaner and offer faster acceleration than an equivalent diesel. They also have the advantage that they can make use of renewable energy sources as electricity generation moves away from fossil fuels to more sustainable alternatives. Not to mention the “sparks effect” that regularly leads to increased patronage on electrified lines brought about by the enhanced image of the service.

Unfortunately electrification does introduce an additional variable into the mix of train reliability due to the additional infrastructure required and as such electric trains are more susceptible to disruption as once the power goes off then that’s it. In many areas electrification also limits the ability to divert trains away from their normal route.

 

[OuterDistant]

I guess it's pro's and con's really.

Like a prison brothel

 

[jopsuk]

Electrics also tend to have longer working lives- especially the motors. There's less to go wrong on electrics, even with fancy three phase motors.

 

[michael769]

Unfortunately electrification does introduce an additional variable into the mix of train reliability due to the additional infrastructure required and as such electric trains are more susceptible to disruption as once the power goes off then that’s it. In many areas electrification also limits the ability to divert trains away from their normal route.

While the power adds an extra failure mode to the infrastructure, electric trains are more reliable than diesels. Can the extra failures due to power/OHL problems possibly be offset by fewer train failures? My own experience of a diesel service that is 75% under OHL is that disruption due to train failures is much more commonplace than due to OHL failures, which seems to suggest they are, at least on my route.

 

[jopsuk]

As for the specific failings of 3rd rail- it was dismissed as "obsolete" some time around 1906 or so by a leading rail engineer- yet the Southern went for it with gusto anyway. The East Coast got the masts too far apart to save money, and the Great Eastern has elderly catenary.

 

[tbtc]

Operationally it'd have been better to have just the one type of electrification in the UK, but there's no way that could change now

 

[Yew]

I would say in locomotives, from a passenger point of view (say a HST vs a 225) there will be more differance from the types of carriages (mk3 or mk4) than from the train at the end (slightly better acceleration from a 91 I would imagine)

However from an MU point of view, EMU's are much better than DMU's Mainly because of a) no engine noise (or significantly less) and b) much less in the way of rattling and vibrations from the seats (once i saw a chapman moving about 2" back and forth from harmonic vibration)

 

[LE Greys]

I would say in locomotives, from a passenger point of view (say a HST vs a 225) there will be more differance from the types of carriages (mk3 or mk4) than from the train at the end (slightly better acceleration from a 91 I would imagine)

However from an MU point of view, EMU's are much better than DMU's Mainly because of a) no engine noise (or significantly less) and b) much less in the way of rattling and vibrations from the seats (once i saw a chapman moving about 2" back and forth from harmonic vibration)

Acceleration is a bit weird. Diesels are capable of giving a certain amount of horsepower and that's it, while tractive effort changes with speed. Electrics have very variable power, but are capable of a virtually-constant tractive effort up to a certain speed, then it drops off, but with variable horsepower. As a result, electrics are excellent for slow-to-medium speed acceleration, while diesels are better with medium-fast, while electrics have better top speeds because of higher top-end power reserves. However, adhesion weight and gear ratio come into it as well.

Therefore, 90 beats HST beats Electra at low speed (high gear ratio on the Electra makes starting sluggish, HST has double the number of driving wheels)
90 beats everything in the 20-60 range, HST and Electra evenly-matched (electric tractive-effort advantage)
90 and Electra about equal in 60-100, HST very close (tractive effort and horsepower about match)
90 "hits the wall" at 110 (gear ratio too low, but I bet they could do 125) HST begins to run out of power above 100 (gravity or light loads can get them above 125 sometimes), Electra just keeps going (more horsepower)

This isn't very exact, but I hope it conveys the general idea.

 

[Smudger105e]

As for the specific failings of 3rd rail- it was dismissed as "obsolete" some time around 1906 or so by a leading rail engineer- yet the Southern went for it with gusto anyway. The East Coast got the masts too far apart to save money, and the Great Eastern has elderly catenary.

Third-rail systems are cheaper to install, compared to overhead wire contact systems, as no structures for carrying the overhead contact wires are required, and there is no need to reconstruct overbridges to provide clearances. There is also much less visual intrusion on the environment.

However as third rail systems present the hazard of electric shock, higher system voltages (above 1500 V) are not considered safe. Very high currents are therefore used, resulting in considerable power loss in the system, and requiring relatively closely spaced feed points (sub-stations). (shamelessly stolen from that reliable source Wikipedia)

I was also under the impression that third rail was better for high speed running, as there is a limit to the amount of pressure a pantograph can apply to the overhead wire, where you can press on the juice rail as hard as you like. There are issues with the pantograph contact at high speeds.