Talk:Single-wire earth return

MALT is a single-phase metallic return distribution system. While interesting for its innovative use of high voltage, it is off-topic because it is not an earth-return system, at least according to the citation, which describes using a second neutral wire. Perhaps it should be in a different article? The removed text follows for reuse. Ray Van De Walker (talk) 07:19, 20 April 2009 (UTC)

These include Tunisia, which has made its own version of the single wire earth return; notably MALT. MALT is used within the country to reduce costs and simplify installation; an approach which is working and has made Tunisia's electricity network one of the best amongst the developing nations. ^[1]

This text refers to a system that that does not use earth return. While rather interesting, it is off-topic. Perhaps it should be in a different article? Ray Van De Walker 03:53, 31 May 2006 (UTC)

At the end of the 19th century, Nikola Tesla demonstrated that by using a electrical network tuned to resonance and using, what at the time would be called, "high frequency", a single wire was necessary for power systems, with no need for a return conductor. In the spring of 1891, Tesla gave a demonstrations with avarious machines before the American Institute of Electrical Engineers at Columbia College. His lecture exhibited this feature, the chief import exhibited that all kinds of devices could be operated thru a single wire without a wired return. The one-wire transmission system was protected in 1897 by U.S. patent 0,593,138, "Electrical Transformer".

This patent diectly deals with this topic. And the text and Tesla's intentions in his one wire system is exactly a "Single wire earth return". 204.56.7.1

I'm seeing a few articles mentioning how an earth ground is used as a "return path" for a circuit. Admittedly, my understanding of electrical engineering is very limited, but I was under the impression that the idea of a literal "return path" through the ground was disproven, and an earth ground is now understood merely as a "source/sink". Reading the article about SWER and ones that link to it, I'm getting impression that there's an electrical path through the ground from a user back to the power plant, which I'm pretty sure is not the case. Could this be clarified? -- User:NewtN Question copied here by C J Cowie 00:21, 8 December 2005 (UTC).

The earth can conduct an electric current, but electric power sources and loads are normally not connected to the earth in a manner that would allow the earth to be used as a return path between the source and load. In fact, power distribution systems are usually designed so that an accidental connection to the earth (a ground fault) will cause a circuit breaker to trip and disconnect the faulted load circuit from the supply.In an SWER system, there is an isolation transformer at the point where the SWER transmission line connects to the normal power distribution grid. One end of the secondary winding of that transformer is connected to the earth. At the load location, there is another transformer with one end of the primary winding connected to the earth. The use of two isolation transformers assures that the earth is used as a return path only between the two isolation transformer locations. -- C J Cowie 00:38, 8 December 2005 (UTC)

Thank you for the comments regarding the isolation transformers. I saw something to this effect in a circuit diagram of a SWER system and I shouldn't have skipped that very important point. My question regarding the terminology "return path" still stands, though. My understanding is that if you grounded these transformers in very large piles of earth that were totally separate and insulated from each other, the system would function equally well. Is that more or less accurate? If so, is "return path" merely a metaphor? If not, does that mean a wave of displaced ions is travelling through from one transformer to the next, heating the ground as their energy dissipates? -- NewtN

I have an electrical engineering degree and working experience, but I am not an SWEW expert, not even an electric power distribution expert. However, I hope that I have enough expertise to be useful. My comments are based on my understanding of some fundamental principles plus my understanding of what I have found on the internet:

http://www.ruralpower.org

http://www.eng-tips.com/viewthread.cfm?qid=122070&page=19 (This is a discussion about another subject, but it contains some comments about SWER in the middle of the main discussion.)

The term "return path" is not merely a metaphor. With SWER distribution, an electric current does actually travel through the earth between the transformers. Electrons are actually exchanged among the molecules of water and other conducting materials in the earth. Since electrons removed from one molecule are immediately replaced by electrons from adjacent molecules, I don't believe that ions accumulate or travel in the earth. There is certainly some power dissipated in the earth as heat, but that effect would be quite small. The transformer windings are connected to the earth by boring holes in the earth and inserting long copper-clad steel rods. If 2 rods were to be driven into the earth at 2 locations along the SWER path, it would probably be possible to measure a voltage between them. It appears that SWER systems are designed to limit the voltage in the earth to 20 volts per meter to avoid shocking people and animals that might be in the area.

SWER systems are used in isolated areas in Australia, New Zealand and various parts of Africa. --C J Cowie 21:31, 13 December 2005 (UTC)

Hi CJ. I added some details to the article just before I read your comments above, but we seem to be saying the same things. I didn't put in anything about the conduction mechanism, since I think that's too detailed for this article, but you might disagree. If you do want to discuss the subject, perhaps it would be better to start a new article on "ground currents" or something, since it will apply to many other articles besides this one. Regards, --Heron 21:57, 13 December 2005 (UTC)

Hi Heron. I had not heard of SWER before I saw User:NewtN's question at Talk:Electrical engineering. My own curiosity prompted me to try to learn enough to answer the question. I think that the brief description and links that now comprise this article are sufficient. Regards, --C J Cowie 23:40, 13 December 2005 (UTC)

Make a reference note to these or leave them out. 204.56.7.1

Maintenance costs are roughly 50% of an equivalent line. numbers from Stone Power reference; 'regulation' from Mandeno who said that the costs were lower.

Steel's greater strength permits spans of 400 m or more, reducing the number of poles to 2.5/km. from Mandeno, who has an extensive discussion on this issue, also briefly but prominently mentioned by Stone Power

Reinforced concrete poles have been traditionally used in SWER lines because of their low cost, low maintenance, and resistance to water damage, termites and fungus. Local labor can produce them in most areas, further lowering costs. Mandeno developed concrete poles, as outlined in article below, and they have apparently become standard in these systems; ruralpower features them, and mentions that local production is an important point.

[several hidden] from Mandeno

standard operating procedure under Mandeno, below

the entire distribution upgrade sequence is ref. Stone Power, below

[several hidden] from Stone Power, below

ref. RuralPower.org

from presentation on Single Wire Ground Return Interties at Univ. of Fairbanks, about alaskan interties, above

Besides the one in the article, please read,

• Nikola Tesla and the induction motor. CM Jarvis - Physics Education, 1970 - iop.org

Also, a simple book search will show that this is what tesla was doing. G.book search. 204.56.7.1 15:36, 2 June 2006 (UTC)

This is interesting, @ the patents of Tesla it states that his patent is cited by U.S. patent 6,104,107 (Method and apparatus for single line electrical transmission). 134.193.168.236 18:42, 2 June 2006 (UTC)

"SWER and conventional single wire rural electrification is generally installed in remote areas and can be prone to energy theft. Methods of countering this include centralized metering at the distribution transformer, prepayment meters and the use of neutral screen service drop cables. " For this to occur a thief must install a transformer and an effective earthing system. Energy theft in a developed country typically occurs by bypassing or in some way retarding the customers meter. In a developing country illegal connections direct to the low voltage street circuits would be more common. In either case comnnections direct to the HV system would be rare. If there is no major objections I will remove this point. Steve 23:04, 15 June 2006 (UTC)

Otoh SWER brings up an intersting possibilty for theft of its own and that is magnetic coupling to the line itself. Not sure how feasible it would be but it would certainly be interesting to run some calculations. As the current in the line is unbalanced it shuold be possible to pick up some significant magnatism without needing to get dangerously close to the line. Plugwash 18:52, 25 September 2006 (UTC)

I vaguely recall Mythbusters having a go at this concept and busting it Lumberjack Steve 00:28, 27 September 2006 (UTC)

If they did i suspect it was for a normal line not a SWER (as SWER basically doesn't exist in the USA). Mythbusters is a long way from rigours science! Plugwash

It was indeed a normal line, but it wasn't intended to be a SWER one. The original myth may have involved one, but if it did, that detail has been lost in time. --StarChaser Tyger 01:09, 22 August 2007 (UTC)

Right, I'm saying that the myth in the case of a normal line is indeed pretty easy to bust (btw most of mythbusters crappy experiments prove nothing that couldn't be easilly calculated and have no scientific rigour at all, mythbusters is entertainment not science). The basic problem is that the magnetic field drops off rapidly because of cancellation between the two lines. SWER on the other hand doesn't have a nearby canceling line so there should be a much bigger field. Plugwash 00:09, 23 August 2007 (UTC)

I agree that, in theory, we expect SWER to have a much bigger magnetic field. And I agree that Mythbusters is entertaining. But disagree with your "not science" comment. Because "Ideas are tested by experiment. That is the core of science." -- Zombie Feynman. :-) --68.0.124.33 (talk) 15:58, 10 December 2008 (UTC)

The current in the ground would be too diffuse to tap into the magnetic field. The magnetic field around the conductor cable is proportional to the current, which would be weak because high voltage/low current is used for power efficiency. And I would guess that most energy thieves don't really want to get close to 22kV !-) Darkman101 (talk) 23:53, 21 May 2014 (UTC)

It's s SWER transformer, the image is taken in CANADA and the history section of the article doesn't mention that SWER lines are used in CANADA.

It's a single bushing transformer but we can't see the overhead line - could well have the neutral wire run overhead. Common as dirt in rural distribution and does not in the least imply earth return. SaskPower Saskatchewan runs some SWER lines for the same reason the Australians do -remote farms many miles apart. --Wtshymanski 17:59, 18 July 2006 (UTC)

I suspect that there is a neutral return wire for this image - you can see a wire running up the pole seperate from the wire to the bushing. Quite common when the economics of the network require SWER but the earth return is not of a high quality ie sandy soil, hard rock etc. Lumberjack Steve 23:14, 18 July 2006 (UTC)

(following comment also posted earlier on talk:split-phase) looking at http://wearcam.org/christina/billru_cottage/d325.jpg which appears to be a larger view of the photo in the article and some of the related images on http://wearcam.org/christina/billru_cottage/polemount.htm it looks like the horizontal wire in the picture is a neutral of some kind with the phase wire being higher up on the pole. Plugwash 00:13, 19 July 2006 (UTC)

to have mutliple SWER lines out of phase with each other from a single distribution point to keep the earth currents at the distribution point down? Plugwash 01:15, 18 July 2006 (UTC)

Yes, that's a great idea. But how is the result any different than standard 3-wire systems?

I was thinking the lines would all start at one point (so you wouldn't have high earth currents at the starting point) but then go off in different directions to supply different loads. Plugwash 21:10, 21 October 2006 (UTC)

According to Stonepower AB, this is a very viable way to upgrade a SWER line, and it does, indeed reduce earth currents. However, Stonepower seemed to recommend that the lines run in parallel on the same poles. If the phases are geographically separated, then the majority of earth current effects, the ones out at customer sites, would still occur. Ray Van De Walker 18:42, 6 September 2012 (UTC)

Obviously it only requires half as many conductors as a two wire system, and 1/3 as many conductors as a 3 wire system -- but the cost of the wire itself is one of the smaller costs in a electric power transmission system.

The article gives 2 other reasons SWER costs less than 2-wire systems:

• SWER's high line voltage and low current permits the use of low-cost galvanized steel wire. Steel's greater strength ...

Huh? No, steel is not stronger than the material used in 2-wire systems. And 2 wire systems also use high voltage / low current.

• SWER also reduces the largest cost of a distribution network, the number of poles. Conventional two wire or three wire distribution lines have a higher power transfer capacity, but can require seven poles per kilometre, with spans of 100 m to 150 m. SWER ... reducing the number of poles to 2.5/km.

OK, so we go from 7/km to 2.5/km. That's wonderful, but why?

Why does SWER need fewer poles?

It can't be because the cables are stronger. (The material used in SWER systems isn't any stronger than the steel cables used in 2-wire systems).

I could speculate that with 2 or more wires, we need more poles to keep the lines from swinging into each other and sparking. While with 1 wire, we just need enough poles to keep the lines from hitting the ground.

But perhaps there is some other reason? --70.189.77.59 21:04, 21 October 2006 (UTC)

This information is from ruralpower.org, which has Conrad Holland P.E., and confirmed by Stone Power A.B. (likewise an engineering group.) I suspect that galvanized wire without cladding has a somewhat better strength-to-weight than clad wire. Steel is stronger than either copper or aluminum, you know. But the information is from them, and they actually build these things. I just write articles as a hobby. Ray Van De Walker (talk) 08:15, 20 April 2009 (UTC)

They do occur, the question is how much, and what's morally acceptable.

"The advantage of such schemes is saving money for a second conductor, because the saltwater is an excellent conductor. Some ecologists claim bad influences of electrochemical reactions, but they do not occur on very large underwater electrodes."

The amount of reaction occuring is relatively small compared to what's expected from the line's power rating, because most of the energy in a high voltage line is delivered by high voltage and relatively small currents flow, so the power P=I*V is large, while the power loss, dependent only on current and resistivity of wire, ${\displaystyle I^{2}R}$stays low. I.e. if the same line carried 800,000 volts, or 101 volts and 1 amps over a 100 ohm line, the IR voltage drop in both cases would be dV=IR=1*100=100 Volts, delivering 1 volt on the other end of the wire out of a 100 V input, or 99% loss, compared to 799,900 output out of an 800,000 V input, or less than 1% loss. This is the reasoning for high voltage, limiting the amps that cause voltage drop, but it's also a reasoning to limit the electrochemical reactions, which as voltage independent and only depend on current, based on Faraday's law of electrolysis.

${\displaystyle m=1/F*A/n*I*t}$

where F=96485 Coulombs/mole charge, the Faraday constant

A=atomic mass, 35.5 g/mole for chlorine atoms from seawater, 16 g/mole for oxygen

n=charge per atom, 1 for chloride ions, 2 for oxygen ions

I = amperage, t=time in seconds

So an 8 amp line would generate m=1/96485*35.5/1*8*(24*60*60)=254 g of chlorine gas in a day, equivalent to dumping 25,400 g of 1% wt bleach, or about 25 kg, 25 liters, about 6-7 gallons of straight bleach into the ocean per day at the titanium cage site in question. The sea and sea biosystems buffer and nullify most of these effects - the ocean is a big place - though there is a theoretically limited buffer capacity, how much is too much. It would be nice to have a study on how much this affects a local ecosystem, compared to, say, human fishing and fish eating, or waste treatment plant effluent releases, on a relative scale, on a dollar per dollar basis - if you can put a dollar sign on damage to the environment due to fishing - and what's acceptable. Humans do inflict some damage on the environment to sustain themselves, including taking over areas from wildlife for agriculture, hunting, fishing, etc., question is how to optimize actions to get the least environmental damage for greatest benefit. For instance fishing is a "natural" process that's been around for millions of years, while chlorine and oxygen induced damaged dna might induce ecosystem changes that are far too great compared to, say, sunlight uv and cosmic ray and seawater uranium decay inflicted dna damages. By the way most public utility drinking water is either chlorinated, oxygenated/ozonated, or treated with UV, to destroy most organisms, and such water, if allowed to stand for long, the organisms that haven't decayed remultiply and the water becomes stale. It's amazing how life is both so fragile and so resilient at the same time. Sillybilly 13:03, 8 November 2006 (UTC)

It's been a while since I last looked her and the article has become a very good reference piece on SWER. It has presented what can be a very confusing engineering concept in simple terms. Well done. Lumberjack Steve 22:42, 24 January 2007 (UTC)

The article has no statement that SWER is an AC low-frequency electricity power transmit technology. This confuses things for a bit. Please make some additions to make understanding faster! thanks! —Preceding unsigned comment added by 91.76.25.177 (talk) 16:39, 11 November 2007 (UTC)

Not quite sure what you mean here - in terms of the frequency it will transmit at whatever is generated 50Hz or 60Hz being the most common Lumberjack Steve (talk) 01:26, 29 November 2007 (UTC)

I added some clarifying text; I myself heard of Tesla's scheme long before I heard of SWER, and I was initially confused. Ray Van De Walker (talk) 08:28, 20 April 2009 (UTC)

Please cite any references or sources. (January 2008) J. D. Redding 15:11, 9 April 2008 (UTC)

The safety discussion is a paraphrase of Mandeno's article, and reviewed by Conrad Holland, P.E., both already cited. If you mean "regulatory" issues, it's the National Electrical Code (obvious to me, I guess), and it's not available on line because it's copyrighted, and the copyright is enforced for safety reasons. It can be purchased here: Ray Van De Walker (talk) 08:16, 20 April 2009 (UTC)

Please cite any references or sources. J. D. Redding 15:13, 9 April 2008 (UTC)

The reliability references are already cited: Mandeno, and also Holland. Ray Van De Walker (talk) 08:00, 20 April 2009 (UTC)

Please cite any references or sources. J. D. Redding 15:13, 9 April 2008 (UTC)

The power quality references are already cited: Mandeno, and also Holland. Ray Van De Walker (talk) 08:00, 20 April 2009 (UTC)

Please cite any references or sources. J. D. Redding 15:13, 9 April 2008 (UTC)

The upgrade recommendations are already cited, see the Stonepower A.B. web site. Ray Van De Walker (talk) 08:00, 20 April 2009 (UTC)

Merging sections and putting one tag ... J. D. Redding 15:13, 9 April 2008 (UTC)

'''THIS ARTICLE IS SUPPORTED BY S.HARIPRASHANTH , WHERE HE HAS DONE A GOOD JOB FOR THIS ARTICLE THEREFORE WE ADD HIM FOR THIS PAGE.

CONTACTS - +94112525081 OR +94115847712

Thank you !!!.

There's a section "use in interties", but with no link to what an intertie is, and searching on Google it appears that entire HVDC lines such as the one on the West Coast of the US are called interties - that's the first result and this page is the second result searching for "intertie electricity distribution". Could someone explain what the definition of an intertie is in comparison to other transmission/distribution systems? Miasmic (talk) 21:26, 10 August 2010 (UTC)

An intertie allows power to flow from one grid to another. It's usually metered so the utilities involved can exchange money for power. An intertie provides alternative or inexpensive power in case generators fail, or lack needed capacity. Interties can be economical when a grid has cheap power and can afford to sell it to neighbors. Ray Van De Walker 15:15, 10 August 2011 (UTC)

Thanks Ray for your explanation. that's a pretty cool coincidence you replied exactly a year (minus 5 hours) after I asked the question. Should have checked my wikipedia watchlist a month and a day ago and made it a annual thingMiasmic (talk) 04:19, 11 September 2012 (UTC)

In the section "Mechanical design" para 3, it says,

"In Thailand the poles only needed to be 1.3m high to allow for the safe passage of the locals."

This sounds like a rather feeble racial joke. Darkman101 (talk) 00:02, 22 May 2014 (UTC)

I think that passage ment "open floating star", or which ever is the most correct name for this now rare configuration. To make it clear, this can be used to provide three phase power with only two conductors; who said the pahse angles must be even if you allow single phase loads in the medium voltage network anyway. The linked Two-phase is almost completely historic.

Some helpful editor has changed it to the correct, still-used "split-phase". Ray Van De Walker 02:24, 23 December 2015 (UTC)

Americans used to do this, I believe. They still may use open wye primary - open delta secondary connection to provide 240 V delta service with only two transformer cans if the medium voltage line is wye with four wires.

Yes. My house is wired this way. Ray Van De Walker 02:24, 23 December 2015 (UTC)

I'm not a professional enough to say why earth-return is never used in multiphase systems. Must have something to do with the earth hawing different impedance compared to the other conductors. (Could be averted with some balacing components; if so, why never used?)

--87.92.152.118 (talk) 17:05, 31 March 2015 (UTC)

I've never been involved with the actual engineering decisions, but I do know that there is an effective, more standardized substitute distribution drop that would serve the same purpose as three-phase earth-return. Three-phase delta is widely used in place of three-phase wye. Delta has no need to distribute a neutral wire for current return and the safety ground is provided locally, or in a substation as a true earth ground. Ray Van De Walker 02:24, 23 December 2015 (UTC)

Mention if Single-wire earth return is ever used on the user side of the power meter. e.g., by individual farm owners. Jidanni (talk) 08:28, 29 May 2019 (UTC)

I have never heard of such an application. Though physically possible, it might contradict local safety regulations. In most areas, a government-licensed engineer is permitted to sign-off on the safety of unusual installations. Ray Van De Walker (talk) 23:20, 2 August 2019 (UTC)

I'm thinking jungle water pump. But my tests with a light bulb showed that a copper return wire made a brighter light... Jidanni (talk) 15:27, 5 August 2019 (UTC)

This is a great piece of trivia, but it's a bit disingenuous to claim that there were no other factors. The cited article actually says that the value of 12 m comes from wanting long, unbroken sightlines between the poles. Where giraffes are mentioned, it says only that "conductor supports" (synonymous with "poles"?) had previously caused problems when placed < 5.2 m off the ground. SuscipiamSingularitatem (talk) 01:42, 9 April 2021 (UTC)