Single Wire Earth Return

Greetings, all. Single Wire Earth Return (SWER) AC power distribution is used in the Australian outback. Does anyone know if SWER is used
anywhere in the US? Thanks for your time and comment. Sincerely,
--
John Wood (Code 5520) e-mail: snipped-for-privacy@itd.nrl.navy.mil

Naval Research Laboratory
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On 3/17/2010 5:41 AM, J.B. Wood wrote:

I think they tried it in Alaska.
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----------------------------------- It has been used successfully in rural areas in Canada. However, this has been discontinued in general -an uninsulated and grounded neutral being used. Part of the reason may be the semi-bogus stray voltage argument (often due to poor secondary wiring -but - hey, lets sue the utility). In one case that I know of , the local telephone company complained- so the utility ran a ground to the edge of town and then dropped it to ground, continuing with single wire, ground return. The "telephone problems" somehow disappeared on their circuits parallel to the power line.
It works but the use of a return conductor works better as it doesn't depend on ground rod systems and good ground paths to keep the impedance low so , as far as I know it is a thing of the past, suitable for low loads widely dispersed. That is, if you can't see your neighbor's place, it works-that should suit the outback.
--
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Don Kelly
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On 3/17/2010 10:38 PM, snipped-for-privacy@shawcross.ca wrote:

Thanks, Don, and all who replied. It seems that saving a few bucks on wire wouldn't offset the disadvantages of using soil in place of copper/steel. I'm an EE by profession (not that well-versed in power distribution systems) but SWER seems kind of silly when all the alternatives are weighed. Sincerely,
--
John Wood (Code 5520) e-mail: snipped-for-privacy@itd.nrl.navy.mil

Naval Research Laboratory
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I did a little research as I was not familiar with this term and was amazed that farmers would even try this, based on my experiences at the company I used to work at. Using the earth as a neutral, particularly in Canada or the northern US where the soil conditions can change dramatically over the course of the year is foolhardy and dangerous. Protection systems, particularly GFI would not work correctly if at all. The farm animals, being 4 legged, are more susceptible to step potential than we are. In a fault condition that step voltage could get quite high.
The research I did came up with a paper written back in 1947 for New Zealand, and a WEB site titled "RuralPower.org" which advocates it but seems directed towards countries like India and Nigeria.
--

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Bob wrote:

I think they did it during WWII. Just about everything was rationed. My dad said he had a Maytag washer engine to pump water for a stock tank. He had it rigged so that the water would short out the spark when the tank was about full. This was back when farmers still had windmills.
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Dean Hoffman wrote:

People did all sorts of stuff back then that would be considered too dangerous now. GFCIs did not exist until decades later, it was still common to build transformerless radios with one side of the line connected directly to the metal chassis, nothing had a safety ground, it's just how it was. During the war when supplies were short, one did whatever they had to in order to get the job done. Safety was a luxury.
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Which war was that ('60s)?
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snipped-for-privacy@att.bizzzzzzzzzzzz wrote:

Scroll up a bit "during WWII"...
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The point being that they were still doing it in the '60s, when "supplies being short" was not an excuse.
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snipped-for-privacy@att.bizzzzzzzzzzzz wrote:

Sure it could be, perhaps the area didn't have a lot of money and it was still considered an acceptable way of doing it? Half the conductors means half the cost. Obviously it did work, even if we wouldn't do it that way anymore. In regions where the ground is moist and relatively low impedance it ought to work pretty well.
Gasoline still contained lead, mercury was still commonly used in household thermometers, kids chemistry sets still used real chemicals, most cars didn't have seatbelts, buildings were built without earthquake reinforcement or fire sprinklers, a lot has changed in 50 years and people are a lot more safety conscious, sometimes even ridiculously so.
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Regions? The entire US? Stop being an idiot.

I see that I'm asking the impossible.
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James Sweet wrote:

It was probably the old 'We've always done it this way' problem, until the old timers retired or died off.
--
Lead free solder is Belgium's version of 'Hold my beer and watch this!'

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Bob The farmers didn't try it. The utilities did. All the farmers did was use the power from the utilities that used the Multi Grounded Neutral (MGN) distribution system that is the standard methodology in public power distribution in North America. I suppose the misunderstanding of what I was saying was my fault because I was contributing to thread drift while replying to Don Kelley's sentence "Part of the reason may be the semi-bogus stray voltage argument (often due to poor secondary wiring -but - hey, lets sue the utility)."
Since I have done rural farm wiring and many who talk about it have never set foot on a dairy farm I take umbrage at people falling for the utility industry propaganda that stray voltage problems are caused by poor secondary wiring rather than by the Multi Grounded Neutral distribution system that would cost the utilities millions to replace. MGN distribution is not widely used in Europe because they learned from our mistakes. Their animal husbandry industries do not suffer from stay voltage problems even though some of their farm wiring also dates from the dawn of electrification. The fact is that the voltages used in secondary wiring on farms in North America are too low to cause most of the stray voltage problems that are complained about by dairy farmers. What does cause quite a few of those problems is the inadequacy of the neutral in MGM utility systems for maintaining a low impedance return path for the High voltage currents in the utilities distribution systems back to their point of origin at the substation transformer. As the neutral return path impedance rises the flow of current through the earth from utility MGN grounds back to the substation grounds and thence to the source at the substation transformer also increases. As the current flows through the earth increases so does the voltage across the surface of the earth through which that current is flowing. It is that increasing step potential that causes the health and behavioral changes in live stock. The stock power utilities allege that the stray current is caused by the condition of the secondary wiring of the affected farms. But if you look at a schematic of a farm's wiring before and after upgrading to isolated neutrals in the entirety of the farms secondary wiring you will find that the stock utilities spin does not stand up to careful scrutiny. In both the before and after case you have a deliberate ground connection at each building on the farm. In the before case those connections are on the neutral in the after case they are on the equipment grounding (actually equipment bonding) conductors. Both sets of conductors provide a continuous low impedance pathway back to the utility transformers secondary and the MGN which is common to both the transformers primary and secondary windings.
The deliberate, code required connections between the farm's secondary wiring and the earth are not the cause of the stray high voltage current that flows over those conductors from the MGN to the superior grounding electrodes located on the farm during that currents travels back to the substation transformers that are the source of the high voltage current in the first place. The utility's MGN grounding electrodes consist of a flat coil of untinned copper wire on the buried butt end of the utility pole or, at newer poles, a single galvanized steel rod driven adjacent to the pole. Notice that driving an eight foot ground rod immediately adjacent to the buried pole is a violation of good grounding practice in that it does not provide an undisturbed shell of soil which is the length of the electrode in all directions away from the rod. Now contrast the likely impedance to earth of those utility installed electrodes on the MGN to the code required grounding electrodes that the electrician or the farmer / rancher her / him self installed on the farm's secondary wiring. On an older farms early technology secondary wiring instead of the aforementioned butt coils and driven rods there will be a metal well casing that is often hundreds of feet deep, underground metal water piping dozens of feet long buried below the frost line, and driven rods at barns and milking parlors that are continuously doped by animal urine thus improving its connection to the earth. While it is true that some of those electrodes will be badly corroded the dairy farmer and her/his stock are better off if those electrodes are poorer than the utilities. In actual practice that is seldom the case. On a newer or newly rewired farm the electrodes are likely to be no less effective. There will be Concrete encased electrodes at each newer farm building that has a concrete foundation or footing. There will be a genuine Ufer grounding array in the floor of any recently rebuilt milking parlor. All of these on farm electrodes are of lower impedance than the utility installed grounding electrodes. It should not be any surprise then that the high voltage return current flows heavily on these distributed private premise grounds that are so carefully and deliberately attached to the utiltity's MGN by the service neutral conductor and the main bonding jumper at the service equipment. (Customer Service Unit for our overseas cousins.) It is this high voltage current flow that generates step potentials beyond a dairy cows tolerance as it spreads out into the earth away from the farms superior electrodes.
Exacerbating that problem is that stock utilities are now managed by bean counters rather than by electrical engineers. As a result of Corporate America's obsession with stock price and quarterly earnings reports the bean counters reduce the staff of skilled unionized labor that maintains the outside plant as a quick way to cut costs. Thus neutral connections on the MGN deteriorate and ground return current rises. There are some utilities, most often consumer owned rural electrification cooperatives, that have addressed these problems successfully. Some have installed special transformers that provide a high impedance on the connection to the customers neutral. Having not had the opportunity to examine one up close I have no idea how they accomplish that. Others have resorted to providing isolating transformers at dairy farms in place of the regular pole pig. Some have also resorted to using transformers with two high voltage bushings in place of the cheaper one bushed one bonded type with the primary connected across two primary lines without an MGM connection on the primary side of the transformer. That latter practice is only effective if it becomes wide spread on any given distribution circuit. What I haven't ween tried that might be both effective and cheap would be to use small light truck mounted drill rigs to rapidly install sectional driven rods to the depth it takes to achieve single digit ground impedances. That technique was often used successfully in McCullough loop fire alarm systems were the back up signal path for the forty eight volt 200 mA current was via ground return.
Ok. I'll put my soap box away now. -- Tom Horne
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Tom, I have often wondered if the impressed current cathodic protection system used on the trans Alaska pipeline causes moose to stop giving milk and thereby causing calves to die from starvation. The impressed current systems use very long anodes run parallel to the underground portions of the pipeline about 6 feet away. The cathode side or negative side is connected directly to the metal pipe. The anodes are a copper wire embedded in a carbon wrap that allows the current to disperse along the entire run which can be up to several miles long per rectifier. The voltage is adjusted to current and can be as high as 30 volts. Moose are common along the pipeline corridor. Civil engineers design these systems for the pipeline company..
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Apples and oranges. They both grow on trees. They both provide food for all sorts of creatures. But you wouldn't call them the same thing now would you. How far does that cathodic protection current have to travel through the soil. Six feet you say verses say six miles. You say the voltage is as high as thirty volts as compared to a rural utility distribution voltage of say 13.9 kV. The current comes from rectifiers so it's Direct Current correct? And this has something to do with High voltage return current from the Multi Grounded Neutral of an AC utility distribution system how? -- Tom Horne
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I suppose it depends on how sensitive Moose are to stepping potentials. I am sure there are potentials in the earth for the distance between the moose feet. Based on the elaborate NEC requirements for equipotential grounding for agricultural buildings to prevent cows from not giving milk I would hypothesize that the cathodic protection systems can cause a problem even at the realtive low voltages. It should at least deserve a stimulus grant for study. The Agricultural people at the University of Alaska recently got a stimulus grant of 1/2 million dollars to study a foreign weed called white sweet clover that has invaded Alaska. The electrical engineering department should get the same amount of money to study the effects of cathodic protection systems on moose (hint).
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Tom Horne wrote:

Actually, as I understand cathodic protection used on mothballed Navy ships, you don't need very much current at all. The idea is to apply just enough voltage to counteract the voltage created naturally by the dissimilar metals in an 'electrolyte'. You could *theoretically* tune it to exactly counteract this potential so no galvanic current flows and no corrosion occurs.
I mean, the stuff the Navy used to protect ships in long term storage was in the mA range. Too high a current and your electrode corrodes away faster than the hull would rust if you have nothing at all. Then you just have a bare wire touching the water line and less protection.
I'd imagine the same is true for this set up, you want a small potential developed to counteract the natural galvanic action, but it doesn't have to be any sort of massive current.
daestrom
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Tom Horne wrote:

<edited>
I would think a wired neutral would be pretty reliable and a much lower impedance than earth return. What problems do you get?

If you have the floor mesh bonded to building ground, and entrance ramps constructed so there is not step potential from ramp to dirt is there still a problem? (Like animals in the yard?) I have read almost nothing on stray voltage.

If the supply is MGN, both of these are just not connecting the secondary neutral to the primary ground return?
Interesting post.
To the original question, I thought SWER/MGN was commonly used in the original US rural electrification - REA (starting about 1935). Rural electrification was expensive because of the low density of users. Has a lot of this been replaced with a wired-neutral/ground?
--
bud--

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It wasn't the farmers who did this-the utility would run a 6900V hot wire and at each service point the transformer was (and still is) connected from this to ground. The ground current would follow the line but its spread would be dependent on soil conditions. I am going from recall in the late 40's, early 50's when rural electrification was new and growing at a great rate. Your NZ paper indicates 1947 which is in that period- and the practice was used by North American utilities such as the then Calgary Power and Canadian Utilities in Alberta and Saskatchewan. If I recall correctly, the first such rural system in the region was installed about 1947 in Swalwell, Alberta. (I am assuming that you are familiar with these names -guessing from your service provider) However, the practice didn't last long (to the mid 50's or so) before a return wire was installed (in parallel with the ground path) so potential problems were recognized.
I hope that I didn't imply that the farmers used the ground as neutral. ----- Don Kelly (also P.Eng retired) cross out to reply
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