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Old January 13th, 2021, 09:38 PM   #1
iant
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Smile USA Farm Power supply

just a quick question
Some of our sheep farms use a SWER (single wire earth return) in Australia
Phase to Earth is 240v
Phase to Phase is 480v
Frequency is 50Hz here
primary supply is 11KV using a centre tap Trans

do you use the same system in remote wiring
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Old January 14th, 2021, 01:32 AM   #2
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Ian - I can remember designing and building SWER transformers in the 60s - yes - bloody old! The biggest issue is when the ground dries out - bad result. Ground is moist or wet not a problem. Even if moist and not wet the losses can be quite high - when dry bugger all at the other end over a long run. Phase to phase is OK but neutral can be really dicky.
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Old January 14th, 2021, 06:58 AM   #3
Lynx777
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I've seen it here in the states a couple of times but only in very remote areas. Once feeding a fire watch tower way out in the woods in a national park and once way up in the Appalachian Mountains.
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Old January 14th, 2021, 09:23 AM   #4
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In the US, rural distribution voltages typically are:
5KV class; 4160V phase to phase, 2400V phase to ground.
15KV class; 12,460V phase to phase, 7200V phase to ground.
Transformers are 3 wire secondary 208V or 240V phase to phase with the center tap (neutral) grounded. Each phase to ground voltage is 120V.
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Old January 14th, 2021, 10:43 AM   #5
Tom Jenkins
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I think most on-farm power is still 240 single-phase 60Hz with a center tap neutral grounded at the service entrance. Some larger operations may have 208/240/480 three-phase 60 Hz. It has been many years since I was on the farm, so maybe someone younger can confirm.
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Old January 14th, 2021, 11:21 AM   #6
GaryS
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The system you described in not used any ware in the US
It is illegal and very dangerous. All electrical must use a clear return path
The ground (earth) return resistance is constantly changing a high resistance would mean lower operating voltage at the point of use. Cattle are more susceptible to the electrical shock or electrocution then people are there bodies are better conductors then the ground they are on, with four legs and overall body length the current will flow through them with bad results. A person could also be in the return path and get electrocuted. The power company where I am requires every 10pole to have the neutral conductor to be grounded they run a copper ground wire down the pole to help keep the ground potential down. I would recommend that you reevaluate using earth return.
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Old January 14th, 2021, 11:39 AM   #7
Lynx777
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Wikipedia, Single-wire earth return

Not saying anything about weather it's safe or not, just that it has been used here in the states. When I came across the installations I mentioned earlier, it was back in the 70's. Maybe it's all gone now. IDK

Last edited by Lynx777; January 14th, 2021 at 11:43 AM.
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Old January 14th, 2021, 02:32 PM   #8
GaryS
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Lynx777
can you get a picture of the transformer service pole on any of those remote locations that use a single wire with earth return
I have been on many remote locations and every one has a natural return while it may be uninsulated and attached directly to the pole but it's their.
as I said before the earth return resistance changes all the time and it would cause the delivered voltage to very greatly you will have nothing but trouble with a system like that it could lead to an electrocution as animals are better conductors then earth
the old telegraph worked that way but they have stopped using it because it was unsafe and they were 48VDC very low power

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Old January 14th, 2021, 04:56 PM   #9
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To save a wire around here, they use corner grounded Delta, so one of the phases is grounded and 480 to the other 2.

Back in the 80's a lot of it was open delta, with no neutral. They changed that to corner-ground around 1990 or so.

The Industrial locations are slowly getting changed to 480Y277 luckily.

I've never run into a ground-return neutral system.
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Old January 14th, 2021, 10:21 PM   #10
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Thanks for the info.
- we have a VSD application ( sorry I can’t give details ) that will work.
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Old January 15th, 2021, 12:31 AM   #11
GaryS
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You are welcome
I assume that you are using a VFD of some sort
I can assure you that the 11K supply line has a return conductor, it just may appear to you as ground (earth) and in fact it should be grounded at both ends but earth in not a conductor
lust make sure you talk to your vender and give them all the information you can to make sure you get what you need the first time
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Old January 15th, 2021, 11:01 AM   #12
Lynx777
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Quote:
Originally Posted by GaryS View Post
Lynx777
can you get a picture of the transformer service pole on any of those remote locations that use a single wire with earth return
I have been on many remote locations and every one has a natural return while it may be uninsulated and attached directly to the pole but it's their.
as I said before the earth return resistance changes all the time and it would cause the delivered voltage to very greatly you will have nothing but trouble with a system like that it could lead to an electrocution as animals are better conductors then earth
the old telegraph worked that way but they have stopped using it because it was unsafe and they were 48VDC very low power
Sorry, no pictures. But what I saw was simply a string of poles with a wire on top. On the last pole hung a small transformer. The one location in the mountains was feeding a small shed with what looked like some weather measuring equipment mounted on top. The fire watch tower (at least i think it was a fire watch tower) was way up in Michigan. Same string of poles with single wire and last pole with a transformer. There was a gate at the bottom the stairs with a single bulb night light. Have no idea if there was anything else up top.

Just to be clear. I saw these installations and think I recognised what they were. I did not install or work on either one.

I agree with you that earth return system has definite safety and reliability concerns and I'm not saying that it should be used. I'm just saying that I saw what I believe to be the earth return system in use. Admittedly I was young and green at the time, so maybe I was missing something.

As a side note. I was stationed in the outback of Australia for a couple of years in the 90's and saw several installations like this feeding the remote ranches in the area. It was amazing to me that even in the dry outback with many, many miles of distance, the system seemed to work fairly well. Some of the residents of the stations did describe to me how in the summer as the ground dried out they would see the lights flicker and dim. One station I visited even had a voltage regulator installed for the radio equipment the kids used to attend "radio school".
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Old January 15th, 2021, 12:34 PM   #13
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Lynx777
I would like to actually see what you were seeing
Because I am sure that you missed a good part of it.
What part of Michigan was this in my guess it the far north just across the border from Canada. I doubt they were built as fire towers they are probably over 70 years old we have some of them not far from me as well when it was a kid we would climb them. My father and grandfather told me what they were for. They were put up during WW2 to watch for unauthorized aircraft crossing the border.
Ground resistance is very important on any system, there are a lot of meters designed just to read it. I have seen grounding systems that were designed as loops and grids of copper wire buried under the floors and foundations of large buildings just to insure the ground / earth would have the same potential sometimes depending on conditions they even have to add chemical salts to the soil to lower the ground resistance. They could never use that as a power conductor.
As an example if you measured just 10 volts between ground point 100 ft apart if you expanded that out to say 2000 ft the voltage potential could be as much as 200v or more and that’s a low example. Another example of why not to use the earth as a conductor
You have a cow standing in middle of a field 100ft from a tree. The tree being the tallest object get hit by lightning the cow 100ft away is electrocuted not contact to the tree at all the distance between the front feet and hind feed caused enough potential / resistance difference to cause the electricity to flow through the cow and kill it. This has been documented. So why would want to risk you animals to that. There is a good reason why they require good proper grounding on electrical systems.
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Old January 15th, 2021, 03:29 PM   #14
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Gary,

Single Wire Earth Return systems certainly did and still do exist. All your points are valid, but that doesn't mean these systems don't exist.

They are typically only found in very remote places that were costly to get power to, and are only valid for low current applications where the voltage rise from the earth return is negligible. They all would be medium voltage, with a mv/lv transformer on the end for the user. The current at MV would be only fractions of an amp.

I still see a few while driving in the central north island here, but have never worked on such a system myself.

I don't believe they are allowed to be installed in new systems anymore, not since our standards mandated the MEN system be used.
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Old January 15th, 2021, 04:27 PM   #15
GaryS
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Saffa
I hate to belabor this point but.
Simple prove it take some pictures of the and post them here or post a link to them on this site I have worked on systems before 1900 single phase, 3 phase, 2 phase (4 Wire) 500DC Generated from MG sets on site double feed substations at 66KV 60hz and 25hz (Railroad) they all have a return line
the fact is that electricity don't work with a return path
I have seen system catch fire and burn up because somebody thought it was a good idea to rout the natural through the earth ground
by the way check the code the natural means that that conductor is bonded (connected to or part of ) earth ground - and structure in some systems a phase wire may be connected to ground but in all cases their is a return path that's basic electric
if you use the earth as a return I can be sure you will have nothing but trouble
you could see voltage fluctuations of over 1000v on the end How's that going to work on your 120v light bulb or an motor
so again I say show me pictures will say it all
and if the farmer has horses they will not stay around with current passing through the earth the can feel it i has witnessed it.
so go ahead and keep believing this false information until somebody get hurt or killed
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