Not a lot of people know this but pure water is classed as an insulator.
By pure, I mean pharmaceutically pure.
I understand that power stations have a station chemist to ensure that pure water is used for cooling the stator windings in a generator. Which are apparently pipes, not solid conductors.
(I am talking hearsay here because it’s not my area).
Probably, adds a little extra spring in the step of the local antelope, No?
Must be why there are so much Springbok in the area 
The Cahora Bassa line also uses an earth return. Then I wondered why there are 2 lines: I found this explanation: The 1,420 kilometres (880 mi) long powerline runs through inaccessible terrain, so it is mostly built as [monopolar] lines 1 kilometre (0.62 mi) apart. In case of a single line failure, transmission with reduced power is possible via the surviving pole and return through the earth.
This is a really, really interesting thread. Thanks to all involved.
On a very practical level, how does one drive in a copper earth rod without damaging the thread at the top?
Use a couple of nuts at the end that extend beyond the thread (and lock them together)
The rods aren’t solid copper so the steel rod is quite hard… 
This is actually quite tricky, you can try locking 2 or so nuts which extends from the thread so yu actually hit the nuts with a hammer, but sometimes this can also bugger up the threads.
I also did one or 2 in the past by drilling a hole in a wooden block then placing the block ove the rod like a cap, then your hammer makes contact with the much larger surface area of the wooden block and doesn’t damage the thread of the rod.
On youtube you will see videos where people drive these with a SDS hammer drill, you get a special attachment for it, but I never tried to find out if they are available in SA.
We have very rocky soil, so what I did with one or 2 very tricky ones was to first knock a gwala in to the ground to make a whole, literally bashing threw some rocks, then the rods went in quite easily.
I lock the two nuts as high up on the thread as I can. Knock the spike in. There will be some damage. After you done with the hammer, just unscrew the top nut completely, it "restores the thread and you re-tighten the same nut after you installed your lug.
The second way is to install your lug before the knock it is. Once the lug is installed, you don’t need to loosen the top nut again. I sometimes install an empty lug, knock the pin in and crimp the lug in place later on…
They do sell a specialised thing that screws on top for this as well, called a “driving cap” “striking head” “driving stud” or similar.
Man, those were nice, but very few electrical wholesalers in SA stock them, I use to ask, but gave up long ago… Maybe I should ask again…
One thing I learned from my father. Never strike the thing directly (unless you know for sure it’s not going to be used again). Wood, if you care about the thing, another piece of steel if you simply want to prevent it from expanding like a rivet head.
That’s a word I am not familiar with. Koevoet?
The electrician for my house insisted on one, along with the special “driving spike” tip that goes on the front, after being looked at like an alien at a few of the local places ac-dc (express) did eventually arrange these for me but it was a 1 or 2 week lead time.
Judging by the reactions I got from most the stores I assume these things are not frequently used.
Many years ago, they were easy to come by, but they disappeared over time, I stopped looking for them all together.
The spike I used had a clamp next to the main rod where the earth cable is bolted on. So I had no issue just banging the spike in with a beeeeeeg hammer.
Can’t remember where I got it from, 90% sure it was builders warehouse.
Whatever you do, don’t force it, use a bigger hammer 
Groetnis
Koevoet ja.
I kind of knew the meaning of the word. I understand it’s Fanagalo for crowbar.
My colleague who has been in mining all his life says: ‘A gwala is a crow bar, as in the expression Chia gwala! Means hit it with the crow bar’
Remembered about this topic again.
Anyone recently found the cap / tool thing with which you can drive in earth spikes, or even better, did someone maybe find the attachment for a SDS drill locally?
In the next few months I want to drive in quite a few spikes, at first 8 and later some more, so I definately want to get something which will make it easier.
Our ground veries from nice and soft to rock hard just a few meters further, a few months ago when installing the electric fence energizer we gave up with one of the earth spikes after a day of trying and grinded off 200mm or so which was still sticking out the ground.
I used this type of spike and just knocked it in with a sledgehammer. No need to worry about the thread getting damaged.