The details are hazy as I recollect this from my nipper days.Many, many years ago.
“Persons were charged with stealing electricity by placing a large coil, somehow, near high voltage AC transmission lines.”
Is this feasible or was it perhaps an April fool’s article that I swallowed hook line and sinker in my youthful naivety.
There is a modern reason for this question.
Due to country wide cable and transmission tower spar actual theft. We are looking at placing modules with a gyroscope and Wifi module to form a mesh that will report if a tower is being “attacked”. Of course I will still have to test if the electronic gyroscope is sensitive enough for this. But one of the problems is going to be, how to power the unit? Solar will require an extra solar panel and battery. If I could tap into the radiated energy from the actual transmission line, great. Many modern SOCs don’t require much power and can sleep most of the time.
To clarify our needs. We are looking at building a device to sense if parts of the metal tower are being removed by scrap metal thieves. If too many parts are removed from the tower. It will buckle and earth the line. This is still at the feasibility stage.
Best Answer
Entirely feasible.
Farmers were occasionally charged with power theft in this country (New zealand) in the past. I haven;'t heard of a case in a decade or few - maybe they are getting cleverer at it :-).
This is the same principle as used for "IPT" / "Inductive Power Transfer as seen in phone chargers, industrial monorail powering, electric vehicle charging and much more.
I started to say that if the pickup coil was symmetrical with respect to two phases that were perfectly balanced that you'd get zero pickup, and then suddenly realised that I've always done IPT with essentially a single phase, and that with a 3 phase system with 120 degrees phase separation you should get the advantage of the full load current even if the two phases were fully balanced.
You are essentially getting fields produced by the current, not the voltage, and the voltage is essentially irrelevant as long as you observe the normal conventions that apply to any other dealing with xxx kV.
Energy Harvesting from Electromagnetic Energy Radiating from AC Power Lines - FAR more energy can be obtained than they achieve.
Worked example - I suspect some of the conclusions are suspect A Solution to the RWP for Exam 1 - Stealing Power
Low technical content - high relevance
Directly relevant but low technical value Electromagnetic Harvesters: Free Lunch or Theft!
Several related stack exchange questions with variably useful content.
How would an electric company detect wireless theft of electricity?
https://skeptics.stackexchange.com/questions/3520/is-it-possible-to-obtain-current-indirectly-from-power-lines
Stealing energy from radio towers or power lines
Online vehicle transfer - I do not have access to this paper but it is probably at least relevant as it will have examples of dual linear conductors and a pickup coil.
Mythbusters getting it wrong
Related:
Industrial monorail
Maximising transfer
Capacitive - but impressive: