I hope that this question is appropriate for this group. I was advised
by a colleague that many of the group regular members were
well-informed.

I have site that has a medium voltage powerline crossing it. I am
engaged in a dispute with the power utility to get the line relocated.
It would bolster my argument if I could show that the electromagnetic
field (EMF) levels were above a certain level. I know the voltage
level and current in amps of the line.

Does anybody know how to:
1. Calculate or estimate EMF at a given distance from the powerline
with data described.
2. Or where I might find on the Web a site that contains table with
precalculated EMF and electric field values for different line types.
I think these are called wire codes in the trade but googling has
produced little of use - I need at this stage expert or experienced
recommendation!

Many Thanks
Martin

"Martin H. Robinson" wrote in message
om...
I hope that this question is appropriate for this group. I was advised
by a colleague that many of the group regular members were
well-informed.

I have site that has a medium voltage powerline crossing it. I am
engaged in a dispute with the power utility to get the line relocated.
It would bolster my argument if I could show that the electromagnetic
field (EMF) levels were above a certain level. I know the voltage
level and current in amps of the line.

Does anybody know how to:
1. Calculate or estimate EMF at a given distance from the powerline
with data described.
2. Or where I might find on the Web a site that contains table with
precalculated EMF and electric field values for different line types.
I think these are called wire codes in the trade but googling has
produced little of use - I need at this stage expert or experienced
recommendation!

Many Thanks
Martin

Buy or hire an emf meter. I hired one as I was concerned about high levels
in my house. I also walked across a local field with power wires across it,
the readings at head height were off the scale. In my house my sons room
had a bad area right where he slept.

I think I hired from healthy house. These people hire all sorts:
http://www.powerwatch.org.uk/sales/equipx.htm

MrCheerful

On 10/02/2004 Martin H. Robinson a wrote :
I hope that this question is appropriate for this group. I was advised
by a colleague that many of the group regular members were
well-informed.

I have site that has a medium voltage powerline crossing it.

I am not suggesting it is inappropriate for this group, but if you want
expert advice on this, then repost your question in
alt.engineering.electrical

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.org

"Steve" wrote in message
...
MrCheerful wrote:


Buy or hire an emf meter. I hired one as I was concerned about high
levels
in my house. I also walked across a local field with power wires across
it,
the readings at head height were off the scale. In my house my sons
room
had a bad area right where he slept.


I would like to see a certificate of calibration from an ACAS registered
standards lab before I trusted a meter to tell me anything.

What is "bad" ? What is "off the scale" nV/m ? V/m If I remember the
thrust of some of the recent "research" it is LOW fields that cause more
problems (if they do) than High fields

Steve

The meter and research on the net gave some suggested figures that were the
maximum to be exposed to. I cannot remember the precise figures that I got,
suffice it to say that the only household problem place was my son's room
and this was caused by the water pipes under the floor acting as some form
of radiating antenna, near which was a very high field.

I mention the power lines as an interesting show of the variations the meter
would show.

The figures indoors where bad were hundreds of times less than below the
power lines.

I am certain that for a court case it would need a calibrated machine with
an expert witness, but I don't believe that is what the OP needs at present.

MrCheerful

MrCheerful wrote:

The meter and research on the net gave some suggested figures that were the
maximum to be exposed to.

The problem is any figures will be based entirely on guesswork - there
simply hasn't ever been any evidence that exposure to such fields causes
any harm, and without such data any figures are meaningless.

--
Grunff

"Steve" wrote in message
...

What is "bad" ? What is "off the scale" nV/m ? V/m If I remember the
thrust of some of the recent "research" it is LOW fields that cause more
problems (if they do) than High fields

I remember hearing a paper by an Oxford academic making this very point -
probably about 8 years ago. Something to do with chemical free-radical
generation at these lower levels.
--
M Stewart
Milton Keynes, UK
www.megalith.freeserve.co.uk/oddimage.htm
http://myweb.tiscali.co.uk/ms1938/

MrCheerful wrote:


Buy or hire an emf meter. I hired one as I was concerned about high levels
in my house. I also walked across a local field with power wires across it,
the readings at head height were off the scale. In my house my sons room
had a bad area right where he slept.


I would like to see a certificate of calibration from an ACAS registered
standards lab before I trusted a meter to tell me anything.

What is "bad" ? What is "off the scale" nV/m ? V/m If I remember the
thrust of some of the recent "research" it is LOW fields that cause more
problems (if they do) than High fields

Steve

On 10 Feb 2004 11:45:42 -0800, (Martin H. Robinson)
wrote:


I have site that has a medium voltage powerline crossing it. I am
engaged in a dispute with the power utility to get the line relocated.
It would bolster my argument if I could show that the electromagnetic
field (EMF) levels were above a certain level.

I don't see how that could persuade them of anything.

Does anybody know how to:
1. Calculate or estimate EMF at a given distance from the powerline
with data described.

Not reliably, there are a number of environmental effects to be
considered and in any case the current flowing in the line will vary
at different times of the day (and on different days). You will need
to carry out field strength measurements. Avoid the toys that
certain anti-power line groups hire out. Apart from their dubious
calibration state they are marked in wholly unrealistic ways showing
false "danger" levels to further their propaganda.

Trying to argue a health case is in any case almost certainly futile.
The studies which will be relied upon by the power companies can be
found at http://www.nrpb.org/radiation_topics/emf/index.htm and none
show any deleterious link between power lines and health. Trying to
refute those will be somewhat difficult.
http://www.spiked-online.com/Articles/00000000551D.htm is also worth
looking at.

--
Peter Parry.
http://www.wpp.ltd.uk/

In article , Harry
Bloomfield writes
On 10/02/2004 Martin H. Robinson a wrote :
I hope that this question is appropriate for this group. I was advised
by a colleague that many of the group regular members were
well-informed.

I have site that has a medium voltage powerline crossing it.

I am not suggesting it is inappropriate for this group, but if you want
expert advice on this, then repost your question in
alt.engineering.electrical

Where you'll probably get quite a range of opinions too!.

IMHO there is, like mobile phone radiation, a lot of research needing
doing into these effects, but I suspect that its not going to make a lot
of moolah for anyone so it isn't a real high priority as such.

I have heard of an anecdotal tale of a number of people who got various
cancers who lived in a house near here that is directly under twin 33 KV
overhead lines.

The current incumbent is a university biological researcher who seems
unfazed by his surroundings, and likes the peace and quiet in his
location, except for damp foggy nights when the wires hum and fizz quite
a bit!......
--
Tony Sayer

The Lord alerted my mind to the presence of this EVIL article by Harry
Bloomfield, and I thusly replied:

On 10/02/2004 Martin H. Robinson a wrote :
I hope that this question is appropriate for this group. I was advised
by a colleague that many of the group regular members were
well-informed.

I have site that has a medium voltage powerline crossing it.

I am not suggesting it is inappropriate for this group, but if you want
expert advice on this, then repost your question in
alt.engineering.electrical

Who died and made you Queen?

--
The Reverend Parson Peter Parsnip
Smiting Sinful Usenet Users Since 1874

"A ******* shall not enter into the congregation of the Lord; even to his
tenth generation shall he not enter into the congregation of the Lord."
- Deuteronomy 23:2

Hi,

If it is that important to you to get the power line relocated then
have you tried asking the power company what they would charge to do
the job?. (I am assuming you have been trying to get them to do it at
their expense - sorry if I am wrong)
Maybe if you were to pay, they would be happy to do it and it may be
cheaper than taking the legal route. You say it is a "site" so I am
guessing you have bought (cheap?) land where the line was already
present. If so, I think you have no chance of getting them to move it
at their cost.

I got the overhead lines into my house (only 240V) put underground. I
dug the trench and they supplied/fitted the cable. It only cost me
£125 - bargain - although medium voltage would undoubtedly cost a lot
more but may still be a bargain if it makes your site a great one.

Costs nothing to find out. Let us all know what they say.

Alan.

(Martin H. Robinson) wrote in message . com...
I hope that this question is appropriate for this group. I was advised
by a colleague that many of the group regular members were
well-informed.

I have site that has a medium voltage powerline crossing it. I am
engaged in a dispute with the power utility to get the line relocated.
It would bolster my argument if I could show that the electromagnetic
field (EMF) levels were above a certain level. I know the voltage
level and current in amps of the line.

Does anybody know how to:
1. Calculate or estimate EMF at a given distance from the powerline
with data described.
2. Or where I might find on the Web a site that contains table with
precalculated EMF and electric field values for different line types.
I think these are called wire codes in the trade but googling has
produced little of use - I need at this stage expert or experienced
recommendation!

Many Thanks
Martin

Just as a follow up I discovered a good resource that might be useful
to others.

National Grid, the UK power infrastructure company, maintains a
website about EMFs at www.emfs.info . Amazingly, given the business
that National Grid are in, it seems to be reasonable enough summary of
the current debate about the potential dangers of EMFs, an explanation
of EMFs and a wide range of links to interested parties including
groups and people who clearly are not lackies or dupes of the
electricity industry.

It is about the best resource that I've seen so far.

regards Martin




(Alan Campbell) wrote in message . com...
Hi,

If it is that important to you to get the power line relocated then
have you tried asking the power company what they would charge to do
the job?. (I am assuming you have been trying to get them to do it at
their expense - sorry if I am wrong)
Maybe if you were to pay, they would be happy to do it and it may be
cheaper than taking the legal route. You say it is a "site" so I am
guessing you have bought (cheap?) land where the line was already
present. If so, I think you have no chance of getting them to move it
at their cost.

I got the overhead lines into my house (only 240V) put underground. I
dug the trench and they supplied/fitted the cable. It only cost me
£125 - bargain - although medium voltage would undoubtedly cost a lot
more but may still be a bargain if it makes your site a great one.

Costs nothing to find out. Let us all know what they say.

Alan.

(Martin H. Robinson) wrote in message . com...
I hope that this question is appropriate for this group. I was advised
by a colleague that many of the group regular members were
well-informed.

I have site that has a medium voltage powerline crossing it. I am
engaged in a dispute with the power utility to get the line relocated.
It would bolster my argument if I could show that the electromagnetic
field (EMF) levels were above a certain level. I know the voltage
level and current in amps of the line.

Does anybody know how to:
1. Calculate or estimate EMF at a given distance from the powerline
with data described.
2. Or where I might find on the Web a site that contains table with
precalculated EMF and electric field values for different line types.
I think these are called wire codes in the trade but googling has
produced little of use - I need at this stage expert or experienced
recommendation!

Many Thanks
Martin

National Grid, the UK power infrastructure company, maintains a
website about EMFs at www.emfs.info

I`ll check that one out myself - but the point that all the nay-sayers
forget about - if you want electric, cables are required - it doesn`t get
around by telepathy.

I haven`t seen many of these activists wanting to get rid of all their
electric and go back to using gas lamps.

As far as EMFs go, you also have to consider "self-inflicted" magnetic
fields - of which many you will come into far closer contact with on a
regular basis.

You can think of your own, but here are few to start you off...

VDU / TV
electric blanket
hair dryer

--
Please add "[newsgroup]" in the subject of any personal replies via email
* old email address "btiruseless" abandoned due to worm-generated spam *
--- My new email address has "ngspamtrap" & @btinternet.com in it ;-) ---

See answers embedded below.....

"Martin H. Robinson" wrote in message
om...
....snipped

I have site that has a medium voltage powerline crossing it. I am
engaged in a dispute with the power utility to get the line relocated.
....it would be easier to give a relevant answer if we knew what the
motivation was (aesthetic, interference/EMC, EM exposure, (or ???) and
whether it's the electric or magnetic field that you're interested in.


Does anybody know how to:
1. Calculate or estimate EMF at a given distance from the powerline
with data described.
....it's easy enough to calculate for single phase (you need to know the wire
separation, height and current) but harder for 3-phase (need to know the
phase sequencing on the wires) and harder still for dual 3-phase - overall
it's probably easier to measure. A 3-axis magnetometer will give you the
magnetic field, the E-field can be estimated if you know the line voltage.

2. Or where I might find on the Web a site that contains table with
precalculated EMF and electric field values for different line types.
....typically between 5 and 100 microTesla except under fault conditions,
e-field depends on line voltage and height.
If your interest is driven by EM exposure considerations these levels are
way below the exposure guidelines.
If you want more info on this there are a variety of sites: World Health
Organisation EMF Project site (loads of authoritative info), UK National
Radiological Protection Board (recently published a review of research and
concluded no proven risk), International Council for Non-Ionising Radiation
Protection (ICNIRP) and so on. If you search on "EC recommendation 519"
you'll find a huge amount of info.
The bottom line is that there's been a phenomenal amount of research in this
area and the only proven and acknowledged effects are nerve stimulation at
low frequencies and thermal effects at higher frequencies. It's possible to
find loads of sensational scare stories but there is NO independently
replicated and peer-reviewed science that supports them (stands back and
waits for tidal wave).

....if your motivation is interference or EMC - the only common equipment
that's affected by this level of B field are CRT-based VDUs (anything above
0.5 to 1.0 microTesla will cause perceptible jitter. Very little is affected
by LF e-fields but ground shift (especially after a line fault) may cause
damage if you have multiple ground reference points.

Many Thanks
Martin

....hope this helps
Dave S

In uk.d-i-y, Jim Michaels wrote:


If you are at all concerned about EMF you should start by eliminating
all rings in the house wiring.

Really. Well well. Fascinating what one learns on Usenet these days.

Maybe you can explain to us all how it is that a circuit - ring, star,
or crop-circle ompholotic spiral - in which the currents 'out' and 'back'
pass in opposite directions in conductors sharing the same outer jacket -
gives rise to an Electro-Magnetik Feeled? (Hint: transformers and other
things with Coils use jsut *one* of the con-duck-tours wrapped around
the iron former).

If you're paranoid about electrickle fields, you'd do better to pay
attention to the layout of your *lighting* circuits, in which the
feed & return (that's live and neutral in your planet's English) are
widely separated, as mentioned here in occasional discussions about
interference with hearing-aid inductive pickups. There at least there's
a mechanism to *produce* a detectable em field; how you then go from
'detectable' to 'brain and health scrambling' is another step, which
might meet with a little scepticism. Still, Gallileo was also ridiculed
in his time, wasn't he...

Stefek

In message ,
wrote:

In uk.d-i-y, Jim Michaels wrote:


If you are at all concerned about EMF you should start by eliminating
all rings in the house wiring.

Really. Well well. Fascinating what one learns on Usenet these days.

Maybe you can explain to us all how it is that a circuit - ring, star,
or crop-circle ompholotic spiral - in which the currents 'out' and 'back'
pass in opposite directions in conductors sharing the same outer jacket -
gives rise to an Electro-Magnetik Feeled?

Not wanting to contradict you too much (don't want to say too much
against the magic force as I earn my living from it), but this is only
the case if the currents and their paths are precicely balanced. In a
radial the current (except under certain fault conditions) will be
balanced, but in a ring, the slightest difference in impedance between
the two halves of the "live" ring and the two halves of the "neutral"
ring could quite easily lead to (miniscule levels of) unbalance.

The fact that the cables are side-by-side, separated by at least 1 cable
diameter doesn't help either. If they were twisted (as in flex or
telephone or computer CAT5) the radiation problem would be lessened
further, and coaxial cables - as generally used by the power companies
for the last leg to your house these days - are the best of the lot,
especially in a PME arrangement when the outer (neutral) is pretty
firmly grounded. I'd expect to see very little field from such a wire.

Not that I'm an expert in EM fields, but I do have a background in audio
where all the above measures (balancing, twisting, coaxial) are put to
incredibly good effect in reducing problems from both radiated and
induced radiation.

Good point about the lighting circuits - there was a discussion here
very recently about that IIRC, and in particular with reference to
hearing aid induction loop coils.

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... 2400 Baud makes you want to get out and push!!

On Wed, 18 Feb 2004 23:36:53 GMT, Martin Angove wrote:

In message ,
wrote:

Really. Well well. Fascinating what one learns on Usenet these days.

Maybe you can explain to us all how it is that a circuit - ring, star,
or crop-circle ompholotic spiral - in which the currents 'out' and 'back'
pass in opposite directions in conductors sharing the same outer jacket -
gives rise to an Electro-Magnetik Feeled?

Not wanting to contradict you too much (don't want to say too much
against the magic force as I earn my living from it), but this is only
the case if the currents and their paths are precicely balanced.

Err, I suspect Stefek was being somewhat ironic........

As I too spent all of my working life within the electricity supply
industry, exposed to varying levels of EM radiation, let's just keep it
in perspective, eh? The levels of radiation in yer average domestic
scenario, or ideed, a 3ph lv overhead line, are infinitesimal compared
to those encountered directly under a 400,000kv dual circuit, or within
a primary or supergrid substation.

In uk.d-i-y, Martin Angove wrote:

In a radial the current (except under certain fault conditions) will be
balanced, but in a ring, the slightest difference in impedance between
the two halves of the "live" ring and the two halves of the "neutral"
ring could quite easily lead to (miniscule levels of) unbalance.

Thanks (genuinely) for making it clear what you meant: yes, if your ring
has f'r example a well-made path to supply Live from both sides but a
looseish connection in one of the Neutral legs, you're right that there'll
be an imbalance in the currentses under such a fault condition. I thought
you were suggesting that in a normal condition, a ring would inherently
produce more of a field 'because there's a loop' than a radial would.

Cheers, Stefek

In message ,
wrote:

In uk.d-i-y, Martin Angove wrote:

In a radial the current (except under certain fault conditions) will be
balanced, but in a ring, the slightest difference in impedance between
the two halves of the "live" ring and the two halves of the "neutral"
ring could quite easily lead to (miniscule levels of) unbalance.

Thanks (genuinely) for making it clear what you meant: yes, if your ring
has f'r example a well-made path to supply Live from both sides but a
looseish connection in one of the Neutral legs, you're right that there'll
be an imbalance in the currentses under such a fault condition. I thought
you were suggesting that in a normal condition, a ring would inherently
produce more of a field 'because there's a loop' than a radial would.


I never suggested anything - that was Jim Michaels. I was just backing
him up slightly using what little knowledge I have of these things.

It needn't be a fault condition which causes an imbalance though, if
tiny is sufficient. But tiny isn't going to cause anyone any harm. I'd
suggest that if there were a large enough imbalance in currents in the
two halves of one leg of the ring to be worried, there probably is a
fault somewhere which should be rectified before somebody plugs two 3kW
heaters into a double socket and melts something.

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... Hey! Your Trakball is upside down!