Introduction to OLE book - free to download

[GazK]

I mentioned a while ago on the GW electrification thread that I was writing a beginners guide to overhead line electrification. It's finally finished and you can download a copy here. It's aimed at people with a basic engineering knowledge and a working understanding of railways, but no other knowledge is required.

There's obviously a great deal of interest and commentary on OLE on these forums - some of it informed, some less so - and I thought this might be of use to those wanting to know more.

 

[snowball]

Many thanks! Have downloaded.

 

[fflint]

Thanks very much for the link GazK.
Hopefully anyone not in the know will read it and have a better understanding of what is involved.

 

[snowball]

I've now read the foreword.

I like your Twitter handle.

 

[coppercapped]

Thank you very much for taking the effort to write the book. It's clear, informative and well organised and it's a great relief not to have to plough through turgid prose.

Excellent - it deserves wide circulation.

 

[J-2739]

Thank you very much for taking the effort to write the book. It's clear, informative and well organised and it's a great relief not to have to plough through turgid prose.

Excellent - it deserves wide circulation.

I agree, I think it would be a good hardcover to refer to for us future enginners.

Thank you ever so much for putting this all together.

 

[GRALISTAIR]

Outstanding - what a brilliant resource. I am going to print and read at leisure. Thanks so much for this.

 

[D869]

An interesting book, thanks for posting.

* * * * * * * * * *

I found the PDF not very easy or pleasant to read on a 1024 x 768 true colour display because the main text font in particular is not "solid" even when zoomed. Blue headings would work better than the red.

 

[nlogax]

Outstanding - what a brilliant resource. I am going to print and read at leisure. Thanks so much for this.

Same here. Thanks GazK - this clarifies so much OLE technical info to me that I've been wondering about for years when staring up from the platform or the train windows.

 

[snowball]

I find it intriguing that the side notches in the contact wire have to have an angle of 78.1 degrees! I wonder where that figure comes from?

 

[LNW-GW Joint]

A remarkable document.
Complete with the history of how OHL systems evolved in the UK and why we have so many variations.
Good to see Series 2 is going to be fit for 125mph.
Many thanks Garry for making your book available.

PS Two tiny typos:
It's London and North Eastern Railway.
And it was the Manchester-Sheffiield and Wath route, not Manchester-Sheffield via Wath (the lines split at Penistone).
I think the MSJ&A route (1931) might deserve a paragraph as the precursor to the later 1.5kV DC main line electrification.

 

[AM9]

I find it intriguing that the side notches in the contact wire have to have an angle of 78.1 degrees! I wonder where that figure comes from?

For consistency it should be specified absolutely, (with a tolerance of course). I suspect that the angle may be an optimised measure that balances the degree (pun not intended) of purchase on the dropper fasteners with the need to maximise the amount of metal in the cross section (to limit electrical resistance). The fact that the nominal angle is a sub-degree number is a human concept. Wire drawing tools and the machines used to make them won't have an issue with achieving and maintaining the value.
I presume that the downward slope is to prevent the build-up of water that may then freeze in the groove, increasing the weight and stiffness of the wire.

 

[Hughby]

That pleasantly whiled away a good hour of a rainy Sunday morning. Well written and pitched at the right level. One of these days I must sit down and really try to understand the Booster Transformer and Auto Transformer arrangements.

I usually get to the station well before my train is due to leave. Am I the only person who can happily spend half an hour gazing at the OHLE trying to work out what is connected to what (and usually failing to make sense of it all!)?

One small typo - section 7.2.2 - there's a digit (5 I think) missing in the list of transformer sizes.
--- old post above --- --- new post below ---

Another suggestion

In figure 32 'Direct Current' is maybe not the best term for the current flow shown in blue as it is still of course an AC flow.

 

[DY444]

Looks to be very interesting - thanks for making it available.

One small point. Figure 7 is Birmingham New St not Euston as stated. The train is arriving at Platform 6.

 

[GRALISTAIR]

One concept I am struggling to come to grips with is around pages 50 -60. It talks about different earths. I always thought earth was earth was earth. So as long as everything was earth bonded ( equipotential) all will be OK. It implies a lineside cabinet can be earth bonded and an OLE mast be earth bonded and yet they are not equipotential. I have a lot to learn - or I am not understanding correctly.

 

[AM9]

One concept I am struggling to come to grips with is around pages 50 -60. It talks about different earths. I always thought earth was earth was earth. So as long as everything was earth bonded ( equipotential) all will be OK. It implies a lineside cabinet can be earth bonded and an OLE mast be earth bonded and yet they are not equipotential. I have a lot to learn - or I am not understanding correctly.

The actual voltage at any given point on an earth conductor depends on its resistaqnce/impedance, and the current running through it.
Thus a lineside cabinet may have a good earth giving a low voltage on a signal system as the conductor performance will be applicable to the power distributed toand drawn by it. I suspect that the load currents are reasonably stable, even when point motors are being driven.
The earth conductors on a traction circuit may be just a few feet away, but with completely different load characteristics and (probably) different feed points, there would be limited, if any correlation between its voltage and that of the signal system with respect to true (as in natural) earth. The traction earth voltage would probably be subject to wild variations of load, including negative load conditions under regenerative power return events.
Despite the difference, it may not be possible to cross bond the two systems for fear of compromising the EMC of the more sensitive signal circuits.

 

[hwl]

One concept I am struggling to come to grips with is around pages 50 -60. It talks about different earths. I always thought earth was earth was earth. So as long as everything was earth bonded ( equipotential) all will be OK. It implies a lineside cabinet can be earth bonded and an OLE mast be earth bonded and yet they are not equipotential. I have a lot to learn - or I am not understanding correctly.

There is always the question of how well objects are grounded (as happened with some platform signalling cabinets and indeed some traffic light control cabinets leading to both being fitted with padded jackets where needed a few years ago).

The resistance of what ever is between those 2 earthing points and hence the route the current will take also need to be taken into account as you can get a voltage rise (along with a drop on the phase cable(s)) along the path taken due to resistive / inductive / capacitive losses between the 2 points.

In the domestic environment the difference is usually* too small to worry about (low single digit volts) but on railways with the juice 100times higher @25KV, larger currents and bigger distance for voltage drop/rise then is a problem!

Also worth while having a read into domestic earthing arrangements and the differences between them (TNC, TNC-S, TNS, TT, IT) and how they influence RCD/RCBO etc. choice as well the actual earthing arrangements and cable sizing with in the home, the railway situation will be more readily understandable after that.

*except Bathrooms, swimming pools and farm yards (with the later the issue is normally with longer 4 legged animals!) hence lower voltages for bathroom fans or isolating transformers for shaver sockets and how metal pipe work is bonded (or not...).

Third rail land is bit easier to understand as the running rails are neutral not an earth and sit on insulating pads. Then there lies the fun of 3rd rail /OHLE parallel running.

 

[GazK]

Thanks to all for the kind words, and for managing to home in on the errors so quickly! Remind me to fire my proof readers.

I've set up an errata page here:
http://www.railwaysarchive.co.uk/OLE/uncategorized/4th-edition-errata-list/

Hughby - I take your point about the use of the term "direct current" but I think in the context of a diagram that's flagged multiple times as being an AC system, it's probably OK.

Sent from my Pixel C using Tapatalk

 

[GRALISTAIR]

Thanks for all your responses. I am a chemist/materials scientist with a Masters in The Corrosion of Engineering materials so I understood the bits about corrosion and materials of construction.

I am really learning about electrical engineering so I really appreciate the education. This board is incredible for learning about a number of disciplines -thanks to all and especially the OP GazK .

 

[Kristofferson]

I've had worse bedtime reading. Always interested in "how stuff works". Thanks!

 

[Elecman]

The requirement of earthing traction systems is not to transfer fault voltage/ currents onto the DNO systems test can seriously affect thier other customers and 3rd parties.

Domestic earthing is designed to provide a very low impedance to earth do that a suitably large fault current flows that guarantees the operation of the protective device in the quickest time possible. Where a suitably low earth impedance cannot be obtained RCDs spared used to provide the necessary protection.

 

[hwl]

Thanks to all for the kind words, and for managing to home in on the errors so quickly! Remind me to fire my proof readers.

I've set up an errata page here:
http://www.railwaysarchive.co.uk/OLE/uncategorized/4th-edition-errata-list/

Hughby - I take your point about the use of the term "direct current" but I think in the context of a diagram that's flagged multiple times as being an AC system, it's probably OK.

Oops forgot to say thanks, obviously a massive effort and really appreciated!!!

One small errata p155 Appendix 1: I can't see the current Gospel Oak - Barking in the TBC or 2016-7 (NR trumpeting the first wires going up at the weekend) also P155 MMLE... Trent Jn?

 

[swt_passenger]

Some comments about Fig 32 if I may, thanks for providing the doc in the first place as well.

The small diagram at the top showing "Actual Autotransformer Arrangement", might be better clearly marked as an 'inset' as it is an explanation rather than an item that is physically present.

Also, should the left hand caption "+25kV OLE" in that diagram be positioned at the top of the coil, rather than the earthy end?

At the left of the diagram, would it be better to change one of the two 'sine wave symbols' to highlight the phase and anti-phase nature of the main conductors?

Agree with an earlier comment that the term Direct Current shouldn't really be used on this diagram, (not that I can think of an obvious alternative). How about supply current and (locally circulating) induced currents?

 

[QueensCurve]

A question about wire tensioning.

Mk3b OHLE had strings of weights running over a pulley. Nowadays the fashion seems to be these "Tensorex" spring thingies.

As a non-engineer my experience is that springs lose their elasticity with time and this may degrade their effectiveness or change the tension. Weights on the other hand will put the same force on the wire throughout their life.

Why has this change been made?

 

[GRALISTAIR]

As a non-engineer my experience is that springs lose their elasticity with time and this may degrade their effectiveness or change the tension. Weights on the other hand will put the same force on the wire throughout their life.

Why has this change been made?

Even (especially) with weights (mass x gravity = weight for the pedants) there will be creep over time.

 

[snowball]

mass + gravity = weight for the pedants

I think you mean times there.

 

[Railsigns]

A question about wire tensioning.

Mk3b OHLE had strings of weights running over a pulley. Nowadays the fashion seems to be these "Tensorex" spring thingies.

As a non-engineer my experience is that springs lose their elasticity with time and this may degrade their effectiveness or change the tension. Weights on the other hand will put the same force on the wire throughout their life.

Why has this change been made?

I understand those weights are quite attractive to metal thieves.

Comments on Appendix A:

- There is an entry for "Shields Jct - Glasgow Airport", with a finish date of 2010, which is curious considering that part of the route was already electrified in the 1960s, while the other part hasn't even been built yet.

- Springburn - Cumbernauld electrification was completed in 2014.

- I don't see an entry for the Paisley Canal line?

Thanks to GazK for making this updated document widely available. I already had a much earlier version with Scott Wilson logos all over it.

 

[GRALISTAIR]

I think you mean times there.

well spotted -thanks - corrected


I loved the summary of the electrification project dates. Amazing.

 

[snowball]

How pedantic do you want us to be about Appendix A?

Huyton to Wigan via St Helens was completed in 2015.

The eastern half of Liverpool to Manchester was completed (or at least was operational) in 2013.

The Whifflet line doesn't seem to be mentioned.

The Glossop spur and Castlefield Junction to Ordsall Lane Junction don't seem to be mentioned explicitly, being presumably implicitly included in the adjacent lines.

Shouldn't Liverpool-Manchester and Manchester-Preston have the plus or minus sign?

 

[Railsigns]

The Whifflet line doesn't seem to be mentioned.

It is mentioned, as "Rutherglen - Coatbridge".