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I have a power line near my house, and for a while now I have been wondering if I can know how much power is being transmitted along that line at a particular time, and in which direction. I could imagine that through measuring electric or magnetic fields I should be able to get some idea of the power. But would that actually work from the ground, with no connection to the cables, and can that be done with equipment that a hobbyist like myself could conceivably get? Or is that signal just way too weak?

Alfred Rodenboog
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You could come up with a SWAG estimate by measuring a voltage and the magnetic field. Telling which direction the power is flowing is not so simple.

Keep in mind that the voltage can be 500,000 VAC with lots of juice behind it. This is a speculation, not a procedure that is healthy to do. If you do anything along these lines, "Don't make an ash of yourself."

I "measured" the voltage of some power lines near my office once by connecting one lead of my volt meter to a good solid ground and the other to a fiberglass fishing pole. I measured the voltage from, say, 30 feet and again from 20 feet below the power line. Using the inverse square property of voltage, I was able to estimate what the voltage would be.

To measure the current, something I've never got working, you need to set up an air-coupled transformer to draw power from the line. The magnetic field of the line is proportional to the current so if you set up a loop of wire that will intersect the magnetic field, the induced current will give you an idea of the current. Keep in mind the there are three phases on the three wires which cancel each other out at a distance. You need to measure one line, not all three. How do you know how much induced current is how much current in the power line? Beats me. Maybe you could say the magnetic field drops off with the square of distance and you could calibrate your equipment using a known current and distance, say using a welder and a tape measure.

If the power line only has two wires, you can guess the voltage but the current will remain unknown. Two wires means DC. There are a few big power DC power lines (such as this) that are 500,000 VDC. Measuring DC current is harder since the magnetic field does not change at 60Hz. I have a Hall Effect clamp on meter that I have used to measure starting current for my car. Could something similar be constructed to measure the power line from a distance? I'm not sure.

user1683793
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