Electronics > Beginners

Isolation transformer and electrons

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IanB:

--- Quote from: nForce on December 13, 2018, 03:43:27 pm ---If we take an ampermeter and connect it in the earth let say 10 meters below ground, then we will measure AC current if we have single wire earth return power system?

--- End quote ---

If you have an ammeter, it has two wires. You are going to stick one wire into the ground? Where are you going to attach the other wire?

Where does the single wire earth return transmission system come into the picture? Is it part of the test or is it far away?

nForce:
We should be in a cave, below ground. One wire goes on one side of the wall the other goes on the other wall. Because of power grid and power stations nearby or above ground, we should measure AC current.

IanB:
Yes, those are called stray currents. They always exist. Occasionally they are harmful and can cause galvanic corrosion on buried metal objects. But mostly they will be negligible.

Stray ground currents are why the London Underground has two insulated power rails and does not use the running rails to return the traction current.

Zero999:

--- Quote from: nForce on December 13, 2018, 07:14:12 pm ---We should be in a cave, below ground. One wire goes on one side of the wall the other goes on the other wall. Because of power grid and power stations nearby or above ground, we should measure AC current.

--- End quote ---

Like this?

Yes, some of the current will flow round the cave and some through the meter.

As mentioned above, they can cause problems, if the system isn't implemented correctly, especially if the ground isn't conductive enough, resulting in a high potential difference gradient, near the transformer.

nForce:
Why didn't you tell me about this at the beginning?

It took 3 pages of this topic just to explain to some beginner that yes an AC current flows in the earth because of the power grid and it's called a stray current.

I didn't know about this, because in convential circuits there is always a return wire. The earth does not look like a wire.

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