A question about how current travels through the real earth?

[HappyHippyDad]

When testing Ze on a TT the only connection between the line and the earth rod is the actual ground.

When you do a Ze is it actually sending a small current through the actual ground from the earth rod at the house to the earth rod at the transformer?

Also, related to the above, I have 2 separate garden light circuits. The customer complained of RCD tripping. The garden lights have junction boxes buried in the ground that lead on to the next light. These Jb's are full of water hence the tripping (IR results 0.006Mohms N-E).

With regards the above paragraph I am getting 0.15Mohms between the Neutrals of both separate garden light circuits (also the earths and line's but you would expect that as light bulbs are in and 0.006Mohms N-E). This is with all the conductors completely isolated, is this again because the separate circuits have a link via the actual ground (due to all the water in the buried JB's)?

 

[happysteve]

Some information on Wikipedia about single wire earth return HV systems (used in rural Aus, NZ etc): Single-wire earth return - Wikipedia - https://en.wikipedia.org/wiki/Single-wire_earth_return

 

[static zap]

The type of current is also important.
AC and DC results are different over time !
(For AC I like to think of lots of capacitors ,rather than weak resistors)...
__Elektrickery__ no weaseling out of it (Aunt Sally)

 

[Lucien Nunes]

When you do a Ze is it actually sending a small current through the actual ground from the earth rod at the house to the earth rod at the transformer?

Yes, although as Des says, there can be multiple paths from the mass of earth back into the distribution system cable as well as the substation earth, via bonded services on TN installations, both TN-S and TN-C-S.

an insulating material is a poor conductor but still a conductor,

Although theoretically true, resistivity is a property that has a wider variation than almost anything in human experience. The conductivity of Teflon is 100000000000000000000000000000000 times lower than that of copper, so it is a little misleading to call it 'still a conductor', when we can use materials 10000000000 times more conductive as insulators. Soil is much closer to copper than to teflon, so that does qualify as reasonably conductive given the rather large cross sectional area available.