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Earth ground is used as a reference from which all voltages are measured in systems which are earth grounded. Because the earth absorbs or dissipates nearly unlimited electric charge, it should always be at an ideal zero or ground potential. (Barring such problems as corrosion or improper grounding.)

I understand that high voltage transmission lines do not simply have a ground at each end of the system; that multiple ground connections are utilized throughout the length of the line to keep things consistent. This is because conductors are imperfect, etc.

My question is, if you could measure the potential difference between two distant points, both earth grounded, using an ideal superconductor, would there exist any difference (if so, why)? Is the "zero reference" on one continent the same as another? Common sense tells me it should be, it's the same earth. Someone asked me whether there would ever be a reason that they differ, and I couldn't say definitively.

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  • \$\begingroup\$ Earthing an HV transmission line would cause fireworks... Its the trannys and generators which get earthed (and towers but unless something goes wrong they're not part of the electrical system) \$\endgroup\$
    – Raggles
    Jul 7, 2013 at 23:49
  • \$\begingroup\$ @Raggles Really? I know the transmission line itself isn't earthed, the towers and related systems are for reference. \$\endgroup\$
    – JYelton
    Jul 8, 2013 at 0:43

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Short answer is Yes.

The differences in geology (chemical, water content, magnetic (Earth's magnetic field), electrical disturbances (including lightning), physical stresses) mean they are different.

Remember the Earth is a rubbish conductor (mixture of insulators, semiconductors, conductors and liquids in random proportions from place to place) so if you tried to harness this I believe you won't get much consistent power.

You might get a huge magnetic input of power during a solar storm due to the changing magnetic field of the Earth as it interacts, but until we can store such unpredictable power, it is of limited use.

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  • \$\begingroup\$ See electronics.stackexchange.com/questions/17354/… for how hard it can be to connect to Earth.. :-) \$\endgroup\$
    – Spoon
    Jul 7, 2013 at 22:58
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    \$\begingroup\$ Also, Earth's magnetic field is moving a little all the time, and normally this isn't a big deal in a small circuit, but integrated over a geographically large area, it can induce significant currents. \$\endgroup\$
    – Phil Frost
    Jul 8, 2013 at 0:50
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Yes, there is a difference of potential between ground at 2 geographic locations. This is why the power company has neutral grounds at poles along the route. They dont want that potential difference to cause current flow in the wrong direction. Go outside and look at the pole line if you have above ground power and you will see that the majority of the poles have a copper wire running down the pole to keep the reference equal along the whole route and ultimately the grid.

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    \$\begingroup\$ Neutral is generally not grounded along the transmission network. (It may be in your location but you should say what this is.) You may be confusing lightning conductors or spark-gap earthing wiring with neutral links. "They dont want that potential difference to cause current flow in the wrong direction." Is there a "right" direction? Welcome to EE.SE. \$\endgroup\$
    – Transistor
    Jun 28, 2023 at 19:19
  • \$\begingroup\$ :) Of course AC being what it is no there is no wrong direction but that being said there is a ground that current "flows" to. In the US we do have a neutral ground. According to the NEC neutral is the nominal return path. Thank you happy to have found you Im sure I will be educated here and hope my small amount of knowledge can help others. I am always open to learning or correction if i dont understand something. ;) \$\endgroup\$
    – Easy Ogre
    Jun 29, 2023 at 12:09
  • \$\begingroup\$ Neutral is so-called because it has been "neutralised" by connection to earth. This is the case in any system, in any country that uses live and neutral. I suspect that if you can get a decent photo of the transmission network copper wire running down the pole that you will find that it is not connected to any of the wires on the pole (which would eliminate the need for insulating hangers on that wire) but is connected to any metalwork on the pole. \$\endgroup\$
    – Transistor
    Jun 29, 2023 at 22:12

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