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.

  • \$\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 '13 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 '13 at 0:43

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.

  • \$\begingroup\$ See electronics.stackexchange.com/questions/17354/… for how hard it can be to connect to Earth.. :-) \$\endgroup\$ – Spoon Jul 7 '13 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 '13 at 0:50

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