Introduction to OLE book - free to download

[snowball]

Oops, sorry!

 

[ironstone11]

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

Why? Does gravity change over time or does the mass of the weights change over time? I think not, to either.

 

[GazK]

Why? Does gravity change over time or does the mass of the weights change over time? I think not, to either.

no but the length of the wire does under tension.

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[ironstone11]

no but the length of the wire does under tension.

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Hence the need to keep the wire at a constant tension by using weights and pulleys or spring tensioners. Weights and pulleys give a true constant tension whereas springs give an approximation to constant tension.

Weights and pulleys if not maintained properly can seize and are prone to vandalism. Not sure about metal theives, I thought the weights were made of concrete.

The main advantage of spring tensioners is on lines with more than two tracks where they avoid the requirement to transfer the tensioning cables from the inner tracks (using more pulleys) to the sides of the track. This considerably simplifies installation.

However, spring tensioners are mechanical devices exposed to all weathers, so there may be maintenance issues with these too.

 

[Railsigns]

Not sure about metal thieves, I thought the weights were made of concrete.

No; they comprise a stack of metal discs. Look at figure 110 in the book.

 

[GRALISTAIR]

no but the length of the wire does under tension.

Which of course is creep.

At one time (you mention it in your book) Cadmium was the alloying element used. It helps alleviate creep.

 

[ironstone11]

No; they comprise a stack of metal discs. Look at figure 110 in the book.

Yes, another source (Network Rail. A Guide to Overhead Electrification) states they are made of cast iron. Makes sense as higher density than concrete. But surprised metal thiefs would be interested.

 

[GazK]

thanks for all the ongoing comments and questions. I will pick up any specific non-appendix comments and deal with those separately. Re: the appendices - to explain a little, these are snapshots of spreadsheets I run at work for general info. As such, they are inevitably less complete than the body text, as they havent been peer-reviewed to the same level. I'll pick up all the suggestions and add them to the spreadsheets, so please keep them coming. I live in a GW bubble so I often don't know what's going on at the other end of the country.

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[Domh245]

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?

In addition to the points already made, one advantage of the Tensorex spring units is that they are compact, and as seen on the GW scheme, can be used 'in-line' ie, they don't need to have trailing wires crossing over other lines to reach the tensioning equipment that would have to be mounted on the uprights of the masts, which has benefits. I think that Phillip Phlopp talked about it a fair bit before.

 

[GazK]

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?

The "actual ATx arrangement" is trying to show that the coils are side by side, and 1A in coil A induces 1A in coil B. The necesssity to make the main diagram readable means the coils aren't depicted side by side, which is the thing that threw my understanding off when I was trying to get my head around AR feeding.

The +25kV label is in the correct place - there is no "earthy end" to that cable, it's the contact wire/catenary! The only thing thats earthed on the diagram is the traction rail.

Regarding the sine wave, that is a good point and one I'm still not sure about. I'll ask some experts...

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No; they comprise a stack of metal discs. Look at figure 110 in the book.

they are typically cast iron, as stated above. Cheap and dense, just like me.

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[AM9]

... But surprised metal thiefs would be interested.

But they steal cast iron drain covers from the streets.

 

[Elecman]

No; they comprise a stack of metal discs. Look at figure 110 in the book.

They are made of cast iron and before closure were nearly all cast at BREL Horwich Foundry. They used to cause great consternation when in production due to thier propensity to come out of the knockout onto the cooling conveyor on edge and promptly roll away at yellow heat across the floor.

 

[snowball]

You'd think they'd have redesigned them to be square or hexagonal.

 

[GazK]

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?

Can you expand on the Whifflet comment? Where to where, and when?

And no, Liverpool - Manchester is boosterless classic so no auto transformers.

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It is mentioned, as "Rutherglen - Coatbridge".

aah thanks - confusion cleared.

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[ironstone11]

The "actual ATx arrangement" is trying to show that the coils are side by side, and 1A in coil A induces 1A in coil B. The necesssity to make the main diagram readable means the coils aren't depicted side by side, which is the thing that threw my understanding off when I was trying to get my head around AR feeding.

The +25kV label is in the correct place - there is no "earthy end" to that cable, it's the contact wire/catenary! The only thing thats earthed on the diagram is the traction rail.

If we are discussing Page 47, Fig 32, the "+25kV OLE" label is in the wrong place. As drawn it is in the same place as the return/earth/ground.

Regarding the sine wave, that is a good point and one I'm still not sure about. I'll ask some experts...

The sine waves in Fig 32 should be shown out of phase. The lower one should be turned upside down.

 

[snowball]

Appendix A, while distinguishing sections fitted with ATs from the time of first electrification, does not show the sections of the WCML (and ECML?) that have been retrofitted.

 

[LNW-GW Joint]

And no, Liverpool - Manchester is boosterless classic so no auto transformers.

There's an AT feed the whole distance from Ordsall Lane to Edge Hill (except the old WCML bit between Parkside and Earlestown).
But not between Huyton and Springs Branch.
The masts going up Lostock-Euxton have insulators for an AT wire.

 

[snowball]

There's an AT feed the whole distance from Ordsall Lane to Edge Hill (except the old WCML bit between Parkside and Earlestown).

And here's an autotransformer station at Ordsall Lane:

https://www.google.co.uk/url?sa=t&r...0uJYvaBaxplVuQ&bvm=bv.139782543,d.d24&cad=rja

(Edit: the one in the picture may not be at Ordsall Lane but the text confirms there is one there.)

 

[GazK]

Appendix A, while distinguishing sections fitted with ATs from the time of first electrification, does not show the sections of the WCML (and ECML?) that have been retrofitted.

correct. And I don't intend it to. It's hard enough keeping that spreadsheet up to date as it is (as you can see from the other comments!)

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If we are discussing Page 47, Fig 32, the "+25kV OLE" label is in the wrong place. As drawn it is in the same place as the return/earth/ground.



The sine waves in Fig 32 should be shown out of phase. The lower one should be turned upside down.

Re: the +25kV label - I'm with you now, I was looking at the main diagram. One for the errata list. God knows how it ended up there.

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If we are discussing Page 47, Fig 32, the "+25kV OLE" label is in the wrong place. As drawn it is in the same place as the return/earth/ground.



The sine waves in Fig 32 should be shown out of phase. The lower one should be turned upside down.

Re: the sine wave, I'm 90% sure you're right but I need to check with our electrical gurus. Hope you don't take offense, but I need to check with a named expert. No "post-truth" in my book!

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They are made of cast iron and before closure were nearly all cast at BREL Horwich Foundry. They used to cause great consternation when in production due to thier propensity to come out of the knockout onto the cooling conveyor on edge and promptly roll away at yellow heat across the floor.

A reputable colleagues told me this morning that they use(d) concrete balance weights on Tyne and Wear Metro. Extra kudos points to anyone who can (safely) get me a photo.

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Re: all the comments about Manchester - Liverpool, I'm going to check with some people who have worked on the project. I'm not sure if any elements are passive or active provision for ATF.

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[Railsigns]

A reputable colleagues told me this morning that they use(d) concrete balance weights on Tyne and Wear Metro. Extra kudos points to anyone who can (safely) get me a photo.

This is the best I can manage right now. It's in the background of one of my photos taken at Pelaw Metro station.

 

[snowball]

On page 37 there's a missing number (probably 5) before "MVA" in the fourth bullet point.

(Edit: already noted by Hughby in #13)

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I think there may be a spurious word "from" on page 46, or else some other words are missing:

"the other half comes from adjacent AT sites, using from current induced in the OLE by the -25kV half of the ATs."