Electromagnetic field and medium voltage power line.

See answers embedded below.....

...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.

...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.

...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.

...hope this helps Dave S
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.