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#9979 05/25/02 07:12 PM
Joined: May 2002
Posts: 68
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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


Be Fair, Be Safe
Just don't be Fairly Safe
#9980 05/26/02 06:41 PM
Joined: Apr 2002
Posts: 2,527
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Moderator
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."

[Linked Image from 67.115.161.42]
(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.
[Linked Image from hfgp.com]


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).]

#9981 05/27/02 11:50 AM
Joined: Oct 2001
Posts: 597
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Member
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 Hildenbrand
#9982 05/27/02 12:58 PM
Joined: Oct 2000
Posts: 5,392
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sparky Offline OP
Member
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....

#9983 05/27/02 03:02 PM
Joined: Aug 2001
Posts: 7,520
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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).]

#9984 05/27/02 11:03 PM
Joined: Apr 2002
Posts: 2,527
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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.

#9985 05/28/02 01:07 AM
Joined: May 2002
Posts: 68
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Member
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


Be Fair, Be Safe
Just don't be Fairly Safe
#9986 05/28/02 11:34 AM
Joined: Aug 2001
Posts: 7,520
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Member
'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).

#9987 05/28/02 01:26 PM
Joined: Oct 2001
Posts: 597
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Member
'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.


Al Hildenbrand
#9988 05/28/02 11:27 PM
Joined: Apr 2002
Posts: 2,527
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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

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