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