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Post Time: 02/07/2007 12:06:35 |
Carol
Total Forum Posts: 4 |
We have recently moved and now have 2 overhead single phase elctricity wires straddled across two poles across our garden. The electricity board tells us these are 11,000 volts and that there is a request from our neighbouring farmer to upgrade these to 3 phase in oder to take power to a house he's planning to build about a quarter of a mile away across the field at the back of us. The present electricity wires run across the full length of our garden/land (about an acre) and over a walled garden where I'm creating a herb and veg garden where I shall spend a good deal of time working as well as sitting. The poles and wires are about 15 yards away from the house. The electricity board tell us that 3 phase will continue to be 11,000 volts. We are concerned about the possible effects of the EMF's, especially in the light of my recent history of ME ( still needing to manage personal energy levels)and having some members of my extended ( visiting ) family with cancer - including young children. There is considerable pressure on us to allow the 3-phase cabling and I would wish to be helpful since it will otherwise cost our farmer neighbour about £30,000 to have the cables sunk underground. I am aware, however, that health has no price on it and wish to safeguard myself and others who visit us who have acute on-going vulnerablities. Nine members of our visiting family and friends currently have or have had cancer. Please can you advise re a) the present single phase situation and b) a possible change to 3 phase?
We are being pressured to make a decision on this ASAP (this week if poss) so any guidance will be gratefully received. Thank you. Carol |
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Post Time: 02/07/2007 12:55:23 |
alasdairP
Total Forum Posts: 173 |
I am concerned that an upgrade to 3-phase is needed to just feed one extra house - I can't see the need, unless he is building a farm complex with a high load demand or has plans for further houses in the future. It doesn't compute for me. The higher the load, the higher the magnetic fields from the cables, although a 3-phase LOAD BALANCED line will produce lower magnetic fields than the same load taken from a singl-phase supply. However, I can see no-way that the 3-phase load will be anything like balanced if it is just feeding one (or two) houses. It may be that the electricity company is using as an excuse to re-inforce their distribution network and them lots of extra power may flow along the line.
Ask them for a copy of their local HV network plans and see for yourself just what the line is feeding. Also, ask if they plan to connect in to any other part of their network - or just feed this new house and the farm. Normal houses only use one-phase of a supply, so a 3-phase supply would not help. It would be possible for a 3-phase supply if the new house was all to be heated by electricity - but I would have thought that was very unlikely and inappropriate in this day and gae (cost and environmental reasons - UK electricity is still only about 36% efficient for heating from production to actual heating).
As you have recently moved, you can give the electricity company "notice to quit" and remove their line from your land (assuming that it is there under a Wayleave Agreement - do you have a copy of the wayleave agreement? - if not, ask your solicitor - it will be with your Deeds). It is not normally advisable to give them notice to quit as they will usually then instigate a Necessary Wayleave Hearing where the arguments will be heard in detail and you may not want such hassle and costs. Sometimes, legal wayleave agreements do not actually exist - you would have a strong case for changes if that is the case.
It is possible that the company has a "permanent easement" for the line, but this would be most unusual for a rural line.
Ask them to produce a paper copy of whatever legal documents the electricity company has - don't believe their word that they have them! They usually do, but there are many missing and if they can't produce one then you are in a much stronger position.
If the line doesn't go along the edge of your land, it is possible for you to ask for a re-alignment of the line at the same time as they upgrade to 3-phase. That would be nothing like as expensive as undergrounding and might keep the line further away from your house and walled garden.
Undergrounding can be a lot less expensive if a local contractor is used to dig and refil the trench for the cable. The electricity companies usually sub-contract the work and add a profit margin for themselves. I think that I would ask for detailed costings of undergrounding your section of the line to discover what the actual costs are and what is being quoted for each part (trench, cable, commissioning, etc). I have known cases where costs have been halved by the locals getting much of the work done by local firms. The cable can go underground just through your property - it just needs extra guy wires to support (tension) the end of overhead line section wooden poles against the tension from the overhead wires. That is standard and common practice and NOT expensive. So so don't let them tell you that it all of the line would need to be undergrounded.
I hope this helps.
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Post Time: 03/07/2007 10:13:27 |
Carol
Total Forum Posts: 4 |
Dear Alasdair,
Thank you so much for your amazingly quick reply!. It was agreat help as we'd had difficulty accessing and downloading other material till then. It also enabled us to have useful info and questions for the electricity board people when they arrived about an hour later! The engineer took emf readings with a special hand held metre both inside the house and at the electricity poles in the garden. Standing beneath the two single phase cables, there appeared to be no real reading at all, 0.01 or 00.00 which really surprised me. He also measured the emf’s at the 3 phase pole going to a property which is about 200 yards away from us. Given that there may well have been little power in use at that time, ( it’s summer and 3pm is a likely ‘low time’) it nevertheless only registered 4 on his metre and he tells us that the European limit is 100.
As you indicated, it would obviously be helpful to know what future building plans there may be which would add to the loading of the emfs once the new 3-phase is in operation. At present the electricity board knows of none though while there is nothing on paper, of course, they quite rightly point out that no-one can say whether there are further plans in mind for more houses to be built near or along side the new farm house & farm shed for which the 3 phase is required. The engineer said that while it could only be a guess, he would doubt that the emf’s would be more that 12 even if supplying several new properties. – would you agree with that? Would it make any significant difference to us if such use of 3 phase is on the existing poles? Would much greater use it make it in your view a better load balanced line possibly giving off less emf’s
We raised the question as you suggested about possibilities of either re-routing the cables or laying them underground just for the stretch of our land but there were two objections: a) extra cost to the requesting customer (this is an entirely private transaction) and b) that they disliked running some cable underground and some over – something to do with making it more vulnerable to lightning strikes and therefore not an option they would wish to take – though the reply was a bit hesitant. I mentioned your advice that doing this was ‘common practice and not expensive.’ But they weren’t going to move from their position (Though I’m not completely convinced that they might not be open to this if we pressed them)
The engineer advised us that the strength of the emf’s whether under or over ground, would be the same since they traveled through earth and buildings etc.
Could you confirm or otherwise for us please that putting the cables underground makes no difference?
I was surprised by the metre readings and wonder (if they are correct) whether you would agree that we shouldn’t now be concerned about giving the go-ahead to have an extra wire put up on the poles across our land – or is there something I may be missing or overlooking here?
Thanks so much for your help and being a professional sounding board and advisor in these matters. It’s very much appreciated. C.
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Post Time: 03/07/2007 15:57:40 |
alasdairP
Total Forum Posts: 173 |
Dear Carol
Your reply actually highlights things I was concerned about. The existing line has fields (assuming his units were consistent) of 0.00 to 0.01 microtesla (uT). No problems are reported below about 0.1 uT and the UK average domestic power-frequency fields from outside sources are between 0.02 and 0.06 uT. So the existing line seems absolutely fine.
The incidence of childhood leukaemia is considered to double by an exposure level of 0.4 uT, anti-cancer drug Tamoxifen stops working effectively at about 1.2 uT, and can have a promotional effect abouve about 0.25 uT and miscarriages in the first trimester are reported to more than double at fields of this level. The UK and the ICNIRP international maximum guidance level is 100.0 uT, but this is NOT INTENDED to protect against cancer effects or any other long-term adverse health effects. It is ONLY intended to protect people from short term acute effects.
The 3-phase line had fields that he measured at 4 uT. This is ten times the level at which childhood leukaemia incidence doubles - despite being lots lower than the official safety limit of 100 uT! As for his suggested maximum in the future of 12 uT - aaagh! - that is 30 times the levels at which the incidence of childhood leukaemia is acknowwledged to have double.
As they obviously don't like the idea of undergrounding a section of the line, then what about a line diversion to the edge of your plot - either just around your plot or by moving the line sideways along a longer length. If the line runs over the same farmer's fields, then the extra expense should not be all that great. Find out how much the suggested 3-phase upgrade would cost the farmer and how nmuch EXTRA it would cost to divert the line to the edge of your land. Put that into context with how much it will cost the farmer to build the new farmhouse (etc).
Greater use would not necessarily balance the line any better - although it should do. Frankly, I am surprised that he measured 4 uT under the existing 3-phase line in July - that suggests that it is not at all well balanced. I would not have expected more than 1 uT (max), probably about 0.3 to 0.5 uT underneath it. The electricity industry website on EMF fields:
http://www.emfs.info/Source_overhead.asp (paste the link into your browser)
suggests a typical maximum of about 1 uT close to an 11 kV line. So, I think the engineer was being very misleading when he was talking to you.
Another idea might be - could they not tap a new 3-phase line to the farm from the line 200 metres away that was measured? Avoiding your length of line completely.
I hope this helps.
Alasdair
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Post Time: 04/07/2007 10:43:21 |
Carol
Total Forum Posts: 4 |
Thanks for this Alasdair –
Your info came as something of a shock and disappointment – just as we were thinking from the apparently low readings, that it might all be ok and we could be of help to our neighbour. – What a shame. It’s particularly pertinent for us since we currently have 5 young children in our extended family one of whom has Leukaemia.
In one final attempt to be as constructive and helpful as we can in the circumstances, please could you give us just two more pieces of info?
1. Do you have any ‘guide lines’ as to how far away from a 3-phase pole/wire is deemed ok?
2. Is the info we received that undergrounding 3 phase makes no difference to the strength and influence of its magnetic field correct in your view?
Thanks again for your help.
Once we have some info on the above we can speak to the parties concerned.
Kindest regards, Carol
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Post Time: 04/07/2007 15:24:21 |
alasdairP
Total Forum Posts: 173 |
(1) Did you check out the existing Wayleave situation as I suggested? That really is important.
(2) At present you have a low power single phase line feeding one(?) farm and, when measured, the magnetic fields were almost zero. That is very good and quite OK.
(3) You won't be able to place restrictions on how much load a 3-phase line can supply in the future and it could easily supply a whole village and the more load it supplies, the higher the magnetic fields it will create.
(4) An 11 kV single-phase line can carry up to about 200 Amps (max). That is 200 x 11 kVA (effectively kW) = 2200 kVA, and is equivalent to 9565 amps at 230 volts (as supplied to houses). Allow a safety factor of about 5 for loading, so say 1900 amps when delivered at 230 volts.
A typical house can draw a maximum of 60 or 100 amps at 230 volts. It is very rare and unlikely that it will draw over 50 amps (usual design rules use about 25 amps per house for working out the capacity of substation transformers).
At 50 amps, the existing line can therefore supply (even with the loading safety factor of 5) 1900/50 = 38 houses to 1900/25 = 76 houses.
So the "need" for the new line just does not seem to be there for one new farmhouse and outbuildings.
I have come to the conclusion that the electricity company probably wants to upgrade the line for their own network reasons and is managing to persuade the farmer to partly pay for the work.
(4) I suggest you take these figures to the farmer and ask what extra load he wants to take from the 11kV line. It may be that he wants a 3-phase supply for some equipment - however maybe the compromise that HE needs to make, in that case, is to only purchase single-phase equipment.
(5) Someone (the farmer or the electricity company) is not being open about the reasons for needing this upgrade.
(6) Latest prices that I have (2007, e-on, Central Networks UK) 11kV XPLE 70mm2 3-phase underground cable costs about £80/metre including trenching when supplied in total by the electricity company. This can be significantly reduced if you get a local contractor to dig and refil the trench. But even at £80/m the cost for 100 metres is £8000, not £30,000.
(6) Especially as you have a child in your extended family with leukaemia, I suggest that you should currently refuse this upgrade until they come clean about the real need for upgrading the line.
(7) The fields from an 11 kV underground cable are effectively less than for an equivalent overhead cable and fall-off with distance MUCH faster (falling to half by 2.5 metres sideways c.f. 10 metres sideways for overhead cables). The fields directly above the cable are similar c.f below an overhead cable as you are much closer to the underground cable.
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Post Time: 04/07/2007 18:17:42 |
Carol
Total Forum Posts: 4 |
Thanks Alasdair
There's a lot to digest here and we're grateful for the info. I don't doubt the need for 3 phase as it's what the farm uses at present, so it's a matter of extending it to the new split site. I can't imagine the need changing at a different but similar site. Interestingly there are 3 phase cables along the road at the bottom of our drive, a field's distance away and they stretch for some distance. We live in farming country which means that there is likely to be a local requirement for the extra power.
We have enquired about the wayleave situation and are waiting for docs to be found and sent to us. We understand from the electricity company that they appear to have been given rights in perpetuity about 50 years ago but we're waiting to have copies of the docs sent to us as well as enquiring about the docs with land registery.
Your costings seem much more reasonable than the ones we'd previously been given, so if that's the case, it takes a considerable burden off our shoulders.
We will think on.
Thanks again,
Carol |
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Post Time: 04/07/2007 21:13:49 |
alasdairP
Total Forum Posts: 173 |
(1) If they have a 'Permanent easement' then it will be for a single-phase 11 kV line and not just 'any line'. You would have a reasonable case for at least a re-alignment at a wayleave hearing and/or Lands Tribunal hearing about upgrading the line. What alternative line routes to the farm are there? You are only looking at about £300 per pole to put a new line of poles in for a new overhead line direct to the new farmhouse and buildings. Might that be a cost effective solution for the farmer?
(2) Unless the farmer is planning a new energy intensive enterprise (such as greehouses or a intensive livestock unit) he should really be able to run it from a single phase supply. I suggest you ask for the projected load figures and exactly what equipment he is proposing to use.
(3) It will be interesting to see what paperwork appears re the deeds etc.
Alasdair
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