Rural Power Line Without a Neutral Safety Issue

How does the 7000VAC get through the transformer to the secondary side to place 7000 volts on the secondary neutral? Unless you are talking about a failure of the transform as a short between primary and the secondary. Should be load devices to shut it down in that case. Each house should have the panel grounded which is bonded to the neutral. In the event of one of the connections to ground becomes an open there are many more in the system. Each house is connected.

With out more specific information on each case. It is difficult to make any conclusions as to the cause of these deaths.

The situation that you describe is common in the U.S.

Like you, I have wondered about this and guessed that the answer is the one that was previously given: there are many ground points for the system.

However in the case that you describe - where there is but one ground point - suppose the ground wire - typically directed to a rod at the base of the pole - were severed.

It would seem that the primary voltage would appear across the gap and, since the center tap on the secondary is bonded to the same ground point, that it too would be at high voltage.

I'm confident that someone who knows this stuff will explain.

You speak of single phase I think.

7000 V a.c. this seems very high for even it peak voltage and not RMS.

A single phase is only one "hot" wire until a device is connected then the a.c. can flow.

The Earth is not part of the circuit and can be even connected to the neutral as in some marine applications.

All electricity is dangerous above a certain voltage.

25 v a.c. p-p or 48v d.c. I think danger starts to arrive.

I think the problem might be bad installation.

If you measure the resistance between the pole knocked into the ground and the generating station I would think it is a large number of ohm's.

Do you mean 700 V a.c. p-p ?

Baffled has it pretty much on the money. However, I think you would find that in the US if a single phase is run, there is also a neutral, not just the HV phase. In less developed areas, as OP stated, it is done to save on wire costs by not running a neutral along with the phase. Along with that often also goes a lower value placed on the safety of the public.

7000V is not far from reality. A common distribution voltage is 13.2kV (L-L), which would be 7620V L-G. That would be quite dangerous if there were a break in the neutral grounding wire, with that voltage across the break.

I may have exaggerated in using the word "common" based on an inadequate sample size, but I can attest that the "SWGR" (to translate the acronym from raw Strine) system is highly popular in Fresno California as well as in Jacksonville Florida. I assumed (without any evidence) that it would be popular in places in-between.

Large areas of central Australia run "SWER" (Single Wire Earth Rethurn) systems, but from my understanding, the earthing at transformer and house box (and other points) ensures the neutral/earth relationship is maintained.

The difference here is that we don't centre tap to get 120V, everything is run as 240V.

Metering has overvoltage protection built in, so if there is a fault, it all shuts down.

In some cases I've seen, it averaged 20km between houses on the lines.

Yours was by far the best and most accurate answer up to now, therefore a GA from me!

South Africa also uses this in very remote areas. I suppose a search for SWER (single wire earth return) will find something. Or try Eskom's site. It is done for economic reasons, but not at the cost of safety, as pointed out in the Australia example. It allows for grid electrification where it is otherwise not economically justified. And now a farmer can actually have a dairy that is on an even cost base with other farmers, for example. Or you can electrify tiny rural villages. And before you ask, photovoltaic systems here are prone to theft (both the panels & the batteries).

The other rumour I heard (not verified yet) is that they sometimes use steel as the conductor, after all calculations are done. It reduces the massive cable theft issues we have here. The loads probably have to be very low for this, otherwise the cable size will require such strong poles that the economic benefit is lost. Usually ACSR is used successfully.

All Hi-Voltage lines [11KV, 33KV, 66KV, 132KV the Transmission Transformers] run only 3wires [hot]

Nutral is produced in 11KV/220V the Distribution Transformers.

I don't know the distribution transformers' voltage in 110V supplycountries distibtion transformers.

OK, Thank you all for your comments. It's interesting to note that this single wire high voltage line is found in many parts of the world. The cases of deaths were related to copper thieves who stole the solid #2AWG ground wire running down the pole to the soil. These "copper bandidos" do this during power failures which are very common here. Unfortunately when the power returns the 7600VAC now appears all over the house on chassis's and ground points electrocuting the user. I was called out to a town near the haitian border where we installed a solar system but with grid power as back up. The grid powered charger had "blown up". Being cautious (I've lived here 42 years and seen some wierd stuff) I use a small, pencil sized, AC voltage sensor. When I got to the site before touching anything I pulled out my sensor and it was beeping when I was 5 feet away from the blown charger. I then went to the power pole and got the same beeping. The ground was gone/stolen. I got a villager to pull the high voltage fuse using a 20' PVC pipe and the trouble cleared. We then regrounded the pole and all was well. I guess I would have been electrocuted if I hadn't done that beeper test. Thanks to all.

Regards.

Earth return systems were in use for Manual telegraphy NOT for POWER DISTRIBUTION.

Can you imagine the danger of Voltage distributed from the Service-Earth & your house????

Specially in rainy days when ground is fairly conductive.

Voltage between both feet while walking.

I have seen this scene on a dog & his handler where Earth was being used as the return path.

And how earthcan replace a conductor.

Astonishing !!!!!

Here is some more reading for you.

http://en.wikipedia.org/wiki/Single-wire_earth_return

Please read out of reference :

Safety

SWER violates common wisdom about electrical safety, because it lacks a traditional metallic return to a neutral shared by the generator. SWER's safety is instead assured because transformers isolate the ground from both the generator and user. However, certain groups claim that stray voltages from SWER can injure livestock.^{[citation needed]}

^{Not only livestock but Men there [Haajee]}

Bare-wire or ground-return telecommunications can be compromised by the ground-return current if the grounding area is closer than 100 m or sinks more than 10 A of current. Modern radio, optic fibre channels and cell phone systems are unaffected.

What is your point? All installation methods offer some risk if not installed properly. This is just another system that works safely, properly and efficiently if installed as designed.

Had to give you a GA for such a fundamental and correct statement.

Livestock is affected by even the tiniest stray currents, very true.

But provided the earth conductor is buried to the correct depth, I do not believe that people will be injured or even notice it.

I am sure that what you say could be true on a badly installed installation. Like using uninsulated (or should I say, not an insulation for below ground usage!) cable to connect to the ground plane for example......as many electricians would believe that insulation was not a requirement in the ground wire!!!! Which of course it is.....

If you look at the ground connection as a resistor say 50 KM long, and the supply as being 5000 volts, then the voltage per km is 100 volts. Therefore the voltage per meter is around 0.1 volts. If you could span with your body even 2 meter, you might measure around 0.2 volts.....

As I said before, livestock may notice that, but humans???

Sorry but this is already fact for over 70 years.

Due to the earth return being deeply buried, its simply not a problem.