Every now and then i'll read something here that'll make me wonder if i've led a sheltered life..
This and and this have me fairly rattled
~( compliments of Bjarney )~


i've so many Q's about this i don't know where to begin....so i'll simply throw it out in hopes that you fella's can answer the call.

Not SWER but hi-side URD concentric-neutral cable, miles away from civilization except for the asphalt road—NE Oregon. Just seemed a bit weird—underground primary and underground secondary to an overhead transformer. It fed a cathodic-protection unit, so there must have been a steel pipeline close by.





[This message has been edited by Bjarney (edited 05-06-2003).]

Bjarney,

When My Wife and I rode the Coast Starlight [Amtrak] from L.A. to Seattle, we [more like I ] saw a lot of poles like the one in the image you posted.

Also saw [what appeared as] one Line of the Primary connected with one Line of the Secondary. I am guessing this to be a Common / Grounded Conductor on both sides [???].

As soon as we crossed into Washington, things were back to "Normal" - Two Wire [or Three Wire] Primaries and all Pots were Isolated [no "Common Line Conductor between Pri. and Sec.].

Thanks for the image and the info!


Scott S.E.T.

this was the best link i could find to describe it... maybe we should go into business with this one wire concept and undercut the big utilities...
http://www.elec.canterbury.ac.nz/ME...%20African%20rural%20electrification.htm

i copied this from a conversation 6 years ago:
"You may not believe this, but in many parts of rural Alberta (Canada) there are single phase AC systems which run with one (1) wire only. The AC neutral is (you guessed it) the Ground. Line voltages are typically 14.4 kV for such systems."

and this link was ok too..... i copied the SWER section below
http://www.holec.com.au/references/basic_elec_theory/distribution_systems.html

SWER Two or Single Wire System (Single Phase)

This system uses one phase of a three-phase system but the return path is via the earth. One side of a transformer primary winding is connected to the active conductor and the other side is connected to earth. These systems are connected to the 22kV and 33kV systems. This means the single-phase transformer voltages on the primary side of the transformer are 12.7kV and 19.1kV respectively.

In Western Australia an overhead earth is used so it is a two-wire system, in other states only the active is on the pole and the ground is used as the return wire.

The return current path goes through the ground or the earth system. A poor or missing earth connection can prevent the flow of current even though the system is still alive. This is true for all circuits, and highlights the need for care when working near system earthing equipment.

Lethal high voltages can exist across a poor or broken earth conductor.

Should be an excellant area to study " Step Potential".

Likely guys the 'step potential' is why this thing died a natural death. Military linemen were taught, and used this, for a long time. The higher the amperage, of course, the worse the problem.

A friend of mine still has pics from an investigation in the late 50's of a line he installed. A group of soldiers in a 6 X 6 had to traverse an area where the line dipped very low. One of the group took what they thought was dry 2X4 to hold the line over the truck.

The post mortem pics show the nail marks from his boots burned into his feet.

This AIN'T something worth studying.

This must not be the most efficent circuit , given earth resistance.
I don't know , or see, much on the secondary configuration, is there a potential , as in some autoX-formers, for the primary to 'loop' through the secondary circuit?


I am in awe here...

That's some interesting info in the links Cindy provided.

I notice in the African studies, they propose that for SWER there should be a minimum of three ground rods, with a conventional 2-wire system where it comes into the populated area of the village.

Noticeable too are their comments about 3-phase not necessarily being the most economical way to supply power to these outlying communities; I don't doubt that where 3-ph is/was considered, this shows a heavy influence from their colonial past (many of these countries having taken British/European conventions in the early days).

As an electronics/radio enthusiast, another reason I would have for not wanting SWER is the amount of stray signals floating around in the earth ready to induce interference into a grounding rod using for telecommunications.

This was apparently a problem when electrification came to some rural areas which were still using earth-return telephone lines.

I can't help but wonder about what effects this system has on "Mother Nature" in the areas where this is used.

Anybody know?

Bill

Bill:
I have been trying to find information on this further than the references posted, and even tried 'keyword' SWER found about 73000 hits one titled Mittelhochdeutsche Texte but nothing on Swer.
Also from what I have heard about stray voltage especially on farms is that even in our area, Ohio that is because the primary is grounded without isolation to the secondary and stray voltage is picked up in barns and by the animals. Now our primary distribution is about 12.8kv and they are talking 22-33kv this sounds extreme and I would think just off the top of my head this has got to cause problems in the area.

-Mark-

Using this setup would be like going back in the dark ages, as the resulting power loss even at 19,100 volts would be quite substantial not even mentioning the potential for the risk of shock. remember the loss of power across a resistance is the same at any voltage. this would be the most unbalance system I've ever heard of. and if the primary was tied to the secondary then the chance of shock would be even more just ask any one who has dealt with stray currents on the egc's just to find out the power company had lost the concentric neutral at the pole or lost it under ground and then the transformer try's to get current through the grounding system. I wish we could stop using a grounding system and an unbalanced system so we could get totally away from stray currents! this would make us change to a different way of protecting from lighting strikes but it can and has been done high impedance grounding systems have been around for awhile and a warning system to detect ground faults and trip a breaker has been used before too this way there is no potential between the current carrying conductors and ground just like in a isolated transformer set up. if every house was fed by a transformer that didn't have the primary bonded to the secondary you would have every house isolated from the next and also from earth an little relay tied between the neutral and ground could trip any breaker and shut that breaker off in case of a ground out since the ocp would now be only looking for shorts between hot and neutral. and also lighting does not want to go to any electrical system it's just trying to get to earth in the shortest way possible. this is why it hits our electrical system most of the time now, because we ground it so why are we giving it a shorter way through our house and not directing it around the house by installing a better grounding system for it to hit. essentially a shorter path to ground this would protect our electronics better too. and in the long run it would save allot of money down the road.
I had seen in a post by an electrician that the ship that he was on, had an ungrounded electrical system on it to prevent shock hazards and electrolysis if the government does this on there ships and thinks it's a good practice then why we cant evolve it in to our power grids and even in to the residential electric

:Wayne

SWER seems like an impossible practice, especially when there are incidents like a fallen line that is turning soil into glass as you "stand by."


(From JLC photo archive)

Most don't realize that Jethro Clampett was a seasoned lineman. It's a little hard to make out, but that's him bar-be-quing some nice fat hog jowls and tasty sqirrelbacks at the end of his hotstick. He came up with a clever can't-lose-'em-in-the-coals hotstick accessory to do it.



Above 600 volts, the rules (especially "earth return") really change.

It been a while, but the guy I talked to at the Alberta electric utility was very helpful, but seemed to indicate that the government enforcers really were concerned about proving and keeping low ground resistance at the load ends of the circuit. I can't remember if they had to test yearly or longer.

Apparently, based on usenet postings, it's also done in very rural Minnestota, Wisconsin or Michigan to a small degree.




[This message has been edited by Bjarney (edited 05-06-2003).]

Sparky,

The key to the success of S.W.E.R. is that it is used for dispersed small loads to quote the first of Cindy's citations.

A friend of mine, recently arrived from S. E. Asia, was amazed to realize that an 18 kW 60 Amp 120 / 240 Volt service was marginal by today's single family residence standards. His expectations were that 2.0 kW was more than could be used. The best wired residences he had known were wired for a max of 2.0 kW.

Al,
2.0KW ?...how do they do it?

still, in theory, the earth must act as a variable resistor per conditions, there must be more loss than a copper return right?
, so why waste it??

Bjarney;
did he mention how the localized earth R addressed?

George;
no argument....

Good point on the widely dispersed small loads. This being Africa they're not going to be using much in the way of electric heating, and as these places ar just getting electricity they certainly can't afford luxuries like air-conditioning.

Although here in Britain we're not up to American levels of service yet, most new homes get a 24kW (100A) supply, and the lowest ratings I've seen still in service are 7200W (30A), although there are very few this low still around.

But it's not necessary to go as far as an Asian country see that in other places they take a different outlook. For example, EDF in France still offers a service option of just 3.3kW.


[This message has been edited by pauluk (edited 05-27-2002).]

sparky--

Sorry... I remember 14.4kV and 15kVA so that would limit return current to about an amp. I think 5 (or maybe 25} ohms was mentioned, but I'm not positive.

My question would be that at a distance of a few feet from the ground rods you might have a reading of 5 to 25 ohms but what about all the way back to where the soiled return path ground is connected at the power co. it has to be very high. and even though the voltage is high enough the power loss accross this resistance has to be high.even at the 19,100kv that cindy stated and at .5 amps \ 5 ohms would be about 1910 or almost 2kw of lost power that the power company has to generate for nothing. no wonder we have power shortages. and also this would only be good for 39.6 amps at 240v at the secondary side of the service. the loss will be much greater at higher loads. or Im I useing the wrong formula? but what a waste, like sparky said. and bill I could guarantee that no earth worms will live under this pole! lol

'27,

I can't quite see how you got those figures. If I=0.5A and R=5 ohms, then power lost is I^2*R = 1.25 watts.

At a line current of 1A the loss will be 1W per ohm of resistance. Because the loss increases with the square of the current, there's good incentive to keep the voltage as high as possible (just as with any transmission line).

'27

The resistance in earth is interesting.

Here's another way of thinking about it.

A village of people, let's say 100, live beside a water source that they use for cooking, sanitation, crops and livestock. The Rural Electrification Assoc. (REA) comes along and offers them 1 Amp at 19.1 kV. The REA substation is 50 miles away as measured down the S.W.E.R. right of way. A single strand of #4 aluminum conductor - steel reinforced (ACSR) is installed to the village.

Everyone decides that a water pump will be powered by electricity, greatly reducing the time spent hauling water, and making it practical to do some irrigation. A 10 HP pump is installed along with a few street lights. The village draws 0.5 Amp @ 19.1 kV with everything running, or 9.55 kW.

One of my references shows #4 ACSR has 0.415 Ohms per 1000 ft. 50 miles of #4 ACSR will have 109.6 Ohms in it!

The voltage drop on the #4 ACSR from substation to village will be 54.8 Volts, but out of 19,100 Volts, that's nothing.

Let's say that the village transformer ground has 25 Ohms resistance to earth. The village portion of the earth return will have a voltage drop of 12.5 Volts.

The substation ground grid will also have a voltage drop as will both transformer impedances, but at 0.5 Amp, they are also small.

The sum of all the voltage drops around the S.W.E.R. circuit won't exceed 100 Volts (which, at 0.5 Amp, is a 50 Watt loss).

Remember, the Earth, (after the contact resistance) is simultaneously an infinite source and a sink of electrons.

SWER sounds questionable to some, but I think this may be a bit worse. {From Joe T’s collection…}
http://www.themeterguy.com/gS582613af887660_jpg.html

that's worse...

That reminds me of a photo I saw of a pole in some poor part of India where people regularly added their own unofficial drops to the lines.

At least this one looks as though they're being metered for it, but it sure leaves something to be desired.

I believe that particular pole was found somewhere in the Caribbean. (Arc picture entry about halfway above revised with historical info/corporate memory.)

OMG, if someone doesnt pay their bill how do they know which one to red-tag ?

I went to Venezuela a long time ago and that was exactly what I saw and the customer did his own hookups right through any open window or hole in the wall.

but electric I thought I wasn't caculating it right as I was trying to figure the voltage drop then multiply divide it into the primary voltage. too late in the evening

[This message has been edited by hurk27 (edited 05-30-2002).]

Re the probable losses in transmission, I've sat down and re-read the whole Canterbury University article in detail.

They mentioned a 25A limit on an SWER feeder. Given that the highest quoted voltage is 19.1kV (one leg of a 33kV 3-ph system) that works out to a maximum loading of approx. 477kVA (they quote 500kVA, but who's arguing? ).

Given an overall ground resistance of 5 ohms that was quoted above, the loss would be 3125 watts, or less than 0.75% of the power being transmitted. Here are some quick figures for other ground resistance values:

10 ohms, 6.25kW, 1.3%
25 ohms, 15.6kW, 3.3%
50 ohms, 31.2kW, 6.5%
100 ohms, 62.5kW, 13.1%
250 ohms, 156kW, 32.7%

That's at full load, of course. At 25% loading (119.375kW, 6.25A) the figures are more reasonable even at high resistance values:

5 ohms, 195W, 0.16%
10 ohms, 391W, 0.33%
25 ohms, 977W, 0.82%
50 ohms, 1953W, 1.64%
100 ohms, 3.9kW, 3.3%
250 ohms, 9.8kW, 8.2%

An umetered loss, a loss to the poco...

True.... But I bet they allow for it in setting their rates, just as they would allow for losses on a Cu/Al line, in xfmrs, etc.

For a 3%-impedance pole transformer, the load loss is {surprise} ~3% at rated.

You bet utilities allow for distribution lossses in their rates.

Really though, without having a peer-reviewed paper on the matter, aren't we all taking pot shots at the real numbers?


[This message has been edited by Bjarney (edited 05-31-2002).]

You're probably right -- Some actual figures from SWER systems already in use would be good.

But however low that ground resistance, I still wouldn't wanna be near a rod that goes straight to a 19.1kV source through a xfmr.

remember those prods we used to get fishing worms to come out of the ground? lol

I have to tell this story.

About two years ago we were called to a large aparment complex. it seemed that when any one would come into contact with any thing that was grounded to the service egc the would recive a shock when we mesured it to a ground rod that we installed about 25' away it was about 56volts but it would vary in perportion to how much load was being pulled on the main service (800 amp) even the transformer pad was hot. we then called the power company and at first they tryed to tell us its on our side of the service but after a call to the companys EE they did some testing and found out the concentric neutral didn't have any current on it. so they pulled up the primary feed and found that the neutral had burned off after they replaced it every thing was fine then the next summer we got called again for the same thing. the power company came back out and when they check the neutral it didn't have any current on it but when the lineman tuched the cable it came back up he found that the preveous lineman had just cut the old neutral off about a foot from where it was bonded to the main neutral, and connected the new run to the end of it. the origenel connection was the resion the first cable burned off. but when the neutral was lost the transformer was pulling power through the grounding system which included the main water pipe which is electricly soiled between two services on another building not far away.we had about 6 amps on the neutral coming from the transformer seconedary. even though the transformer has its own ground rod.and there was two ground rods at the service on the building. then a one ott wire to the water main and the reverse at the other buildings. how could there be this much voltage drop across these grounds? the water pipe was amp probed at the other buildings to make sure it was continous.

Talked to a linesman today about this....

He said that they loose primary noodels all the time, sometimes with no customer complaints at all!

makes ya think.....

Great graphic Steve!