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#143261 - 06/18/05 08:16 AM health & high voltage  
kiwi  Offline
Member
Joined: Dec 2004
Posts: 354
christchurch new zealand
A big topic of discussion here in NZ right now is ELF emmissions in the immediate vicinity of overhead HV transmission lines and the effects on the human nervous system.

A recent T.V. documentary here showed a meter which measured 0.1 micro- teslas in a typical home with the fridge and the T.V. on. Then measuring 1.5 micro teslas in the back-yard of a house directly under a 220kV transmission tower.

The World Health Organization recommends that 0.1 micro-teslas are O.K. but 1.0 micro-teslas are not O.K.

Italy and one other European country have now legislated to segregrate HV transmission lines from residential land.

Does anyone else have any ideas on the elf emission debate ?

Would an earthed shield around the HV lines running over houses solve this problem ?


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#143262 - 06/18/05 11:17 AM Re: health & high voltage  
C-H  Offline
Member
Joined: Sep 2002
Posts: 1,497
Stockholm, Sweden
My view on this is extremely biased as I install equipment that exposes the operators to magnetic fields far greater than this. Sometimes the operator has the electrodes touching the body with 10kA flowing in them. In the conductors, not the operator [Linked Image] As the electrodes are about a foot apart, the magnetic field cancels some distance away from the electrodes. Nuts and other small metallic objects have a field day near the electrodes...

As far as I know, there haven't been any recorded short term effects on people from this despite half a century of widespread use.

Long term? Don't know.

Would I want to live right under a 220kV line? No! Apart from EMF, those wires can come crashing down. Not to mention bird droppings from the chatter party on the wires...


#143263 - 06/18/05 08:15 PM Re: health & high voltage  
gideonr  Offline
Member
Joined: Dec 2004
Posts: 161
Edinburgh, Scotland, UK
Anyone who lives near the Underground (Subway) in London will also be exposed to large fields as the trains run on dc and tend to pulseate as the contact with the rail/cantenary varies.

You could only effectively sheild with some kind of ferrous material which would be impractable for a whole house.

In any case, at what level is the increased risk? We have Radon gas seeping into some houses here, and people still smoke cigarettes!


#143264 - 06/18/05 08:55 PM Re: health & high voltage  
Alan Belson  Offline
Member
Joined: Mar 2005
Posts: 1,803
Mayenne N. France
And the same people who prattle on about 'Pylons', give their young children mobile phones.


Wood work but can't!

#143265 - 06/19/05 05:22 AM Re: health & high voltage  
jooles  Offline
Member
Joined: Sep 2004
Posts: 93
brussels, belgium
We were looking once at houses in Portugal to buy. The idea was to use it as a holiday home and to rent it out when we don't want to use it ourselves.

There was one in particular that was beautifully appointed and would have been superb, but for the power lines whose path swooped straight across the upstairs balcony! The lines looked as if they where close enough to touch, although there was a perfectly safe clearence -- it was the optical illusion of being right under them.

Not sure of the voltage: I would guess it was 150kV, but the line was buzzing like a hiveful of bees. The internet says there is an effect called Corona discharge that causes this noise.

Whatever the scientific evidence for the risks of electric and magnetic fields, I'd rather not risk being deprived of a good sleep because if it sounds as loud as that in the day, then at night it would be intolerable.

The only good thing would be that thing of standing under the lines with an old flourescent tube and playing 'light sabers', but I should think the novelty would probably wear off very quickly [Linked Image]


#143266 - 06/20/05 10:25 AM Re: health & high voltage  
djk  Offline
Member
Joined: Dec 2002
Posts: 1,237
Ireland
What I don't get is that there is no evidence of massive cancer clusters in power workers. Lets face it, someone who's has spent their life ontop of, beside, sitting on, having lunch near etc high voltage AC cables would be the most likely person to have any problems.

So, I'd say if the power workers have been doing it for over a century it can't really be that big of a deal.

I'd agree though, I wouldn't fancy a power line that close to my house. Noisy and ugly!

I'd be far more concerned about getting sunburnt than I would be about A/C power lines to be quite honest when it comes to cancer risks.

Smoking, Pollution, excess use of volitile cleaning chemicals, pesticides, radon gas, dental and medical xrays and their overuse.. food additives etc seem to pose far more of a risk.

I'm not even very concerned about mobile phones. Ionising radiation sources and chemicals are what worries me most!

[This message has been edited by djk (edited 06-20-2005).]


#143267 - 06/20/05 07:50 PM Re: health & high voltage  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,217
SI,New Zealand
Dave raises a very interesting point here.
We are monitored here annually with various tests to make sure that nothing untoward is going on with our bodies.
I have to agree though, surely anyone that works that close to the lines, has to be a litmus test for everyone else.
However, this aspect of the power-lines vs. cancer has never even been mentioned.
Instead, the media tends to go for the more emotive side of the story.
One thing that a lot of people here in New Zealand seem to forget, is the fact that in a lot of places, the Asbestos pipes that fed water to thier houses are either still in the road or have only just been removed in the past few years.
It seems that people here only blame things that they can see. [Linked Image]
Another thing about using a Gauss meter is the rule of distance when it comes to radiation sources, I can't be sure, but I seem to remember that the field strength decreases by a multiple of 4(?) of any unit distance away from the source.
{Could someone please correct me if this is in-correct?}
Quote
Italy and one other European country have now legislated to segregrate HV transmission lines from residential land.

In my opinion, this whole problem has come about by urban sprawl, the power lines were more than likely there before any housing was.
To a degree, any councils and developers really need to bear some of the blame for the reason why houses are under the lines in the first place.
Quote
Would an earthed shield around the HV lines running over houses solve this problem ?

In a word, no, in fact it would cause more problems than what it would solve.
At 110 or 220kV, the Eddy currents flowing in the shield would be horrendous, not to mention the problem of Flash-over between the bare line and the shield.
The last thing you want near an HV or EHV line is an earthed conductor anyway, that's why they use insulators on pylons.


Let's face it, these days if you're not young, you're old - Red Green grin

#143268 - 06/27/05 03:45 PM Re: health & high voltage  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Quote
What I don't get is that there is no evidence of massive cancer clusters in power workers.


Nor is there any evidence of such in telephone switchmen, who for over a hundred years have worked in equipment racks surrounded by coils, solenoids, and relays generating various steady and pulsing fields.

If there was any real concern, surely we would have seen some sort of higher average occurrence rate in those exposed to strong fields regularly by now?

Quote
I'm not even very concerned about mobile phones.

Over in North Walsham -- about 10 mi. from here -- there's a protest going on about the new TETRA antennas which have recently appeared on the town's police station. It's funny how the people never complained about the old VHF and UHF antennas, which have been there for years.

I've never heard of any protests over UHF TV masts either, which on the upper end of the band are on near-enough the same frequencies as cellphones, but with a much higher ERP.

Have a look at this site and see what you think:
http://www.emfs.info/



[This message has been edited by pauluk (edited 06-27-2005).]


#143269 - 06/27/05 05:49 PM Re: health & high voltage  
djk  Offline
Member
Joined: Dec 2002
Posts: 1,237
Ireland
The ironic thing about mobile phone mast protests is that the bigger number of masts that go up the weaker the signals you're going to be exposed to are.

i.e. if you're in a good coverage area your mobile uses far less power to connect to the cell mast!

----

Also, with regard to the transmission systems for TV and Radio. In modern radio and tv systems operating on FM/VHF/UHF you usually have a network of small repeaters covering a small area with relatively low power signals, much like a cellular telephone network. However, in the old days you had truely scary AM and VHF towers that broadcast using brute force technology i.e. just pumping in huge amounts of power from a single site.

Modern technology is probabally a lot healthier.

There are a few things when it comes to cancer risk:

1) Cancer's now being diagnosed more effectively where as decades gone by it was often undetected and the symptoms may have been attributed to something else. So, rates may not be actually rising, but rather detection.

2) We're sorrounded by known carcenogens, yet we choose for whatever reasons to ignore them.

The fundemental people have to get into their heads is that life is carcenogenic generally. And living will lead to your eventual demise!


[This message has been edited by djk (edited 06-27-2005).]


#143270 - 06/28/05 09:54 AM Re: health & high voltage  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Quote
if you're in a good coverage area your mobile uses far less power to connect to the cell mast!

Maybe we need a campaign to educate people on this subject? How many times have you heard somebody going on about the radiation from the cell-tower, yet not say anything about the field from their own cellphone?

I'm sure you must have tried to explain the inverse-square law too. I've tried dozens of times, but I'm not sure whether I've always been understood or believed.

Quote
However, in the old days you had truely scary AM and VHF towers that broadcast using brute force technology i.e. just pumping in huge amounts of power from a single site.

Back in the early days of TV when the BBC was still broadcasting from the Alexandra Palace transmitter my family lived in a part of North London just up the road. That was before my time, but my parents assured me that they could get a viewable picture with nothing connected to the average set, and an absolutely perfect picture with just a couple of feet of wire hanging out the coax socket. That was Ch. 1,, so fairly low freqencies (~45MHz), but it still must have been a pretty high field strength.

I still remember the announcements from Radio Luxembourg when I used to listen in the early 1980s: "This is RTL Radio Luxembourg on 208 meters, 1440 kilohertz, broadcasting with one million three hundred thousand watts of power!" [Linked Image]

If you lived next door to their AM array I reckon that with suitably placed coils you could get enough free power to light your house! [Linked Image]

Quote
2) We're sorrounded by known carcenogens, yet we choose for whatever reasons to ignore them.

Yep, there is more than one variable in the equation, which makes objective comparisons that much more difficult. Even finding a suitable section of the population to use as the control is going to be tricky.

Quote
And living will lead to your eventual demise!

Hey nobody told me that when I started out on this adventure. I've been conned! It's not fair! [Linked Image]



[This message has been edited by pauluk (edited 06-28-2005).]


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