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This is a follow-on question to an earlier question of mine; I think it deserves its own question, though.

I am trying to learn as much as I can about how current in a power grid (transmission and distribution) returns to the substations, power plants etc.

In researching this, I came across the claim that in Minnesota in 1995, 59% of the power returns from the consumer to the substation through the ground rather than the neutral wire. On the face of it, I find this number hard to believe, and am looking for an explanation.

The source was given as "Hendrickson, R.C., Mike Michaud and Alvin Bierbaum. 1995. Survey to Determine the Age and Condition of Electric Distribution Facilities in Minnesota: Report 1: Analysis of Overhead Distribution Feeder Testing Data. Minnesota Public Utilities Commission. May 18, 1995" but this does not appear to be available online.

I can think of a few potential explanations:

  • Is SWER widely used in Minnesota? I found some mention in passing that SWER is used somewhere in the upper Midwest, but not where, specifically.
  • Three-phase distribution systems out of perfect balance without a neutral wire would also cause ground current.

Are there any other explanations?

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  • \$\begingroup\$ Isn't that because of where the neutral-Earth connection is made (I'm from EU, I expect you have a residual current protection system)? \$\endgroup\$ – Mister Mystère Apr 6 '15 at 19:25
  • \$\begingroup\$ No, because in a normal two-wire distribution system, there should never be any current to ground. Normally, all current should go through neutral. If you actually have current going to ground, that's considered a ground fault (and would trip up ground fault circuit interrupters). \$\endgroup\$ – Kevin Keane Apr 7 '15 at 5:40
  • \$\begingroup\$ I am aware of that, but the neutral and earth are connected somewhere before the residual current devices to allow the detection of an accidental connection of live with earth. Perhaps the residual current device is in the substation, and then ground is used to carry the current to save wiring costs? I can't explain the 41 remaining % though. \$\endgroup\$ – Mister Mystère Apr 7 '15 at 10:05
  • \$\begingroup\$ I cannot imagine it to be for any reason other than prevalent use of SWER. Surely it would be easy to find out by contacting the relevant electrical authority for Minnesota to see what they use? Electricians will need to know what system is in place before they do work, so I imagine it must be very easy to find out. \$\endgroup\$ – CL22 Apr 7 '15 at 18:02
  • \$\begingroup\$ @MisterMystère - thank you for that thought! What you describe is actually SWER (Single Wire Earth Return), where the electricity is delivered to the end user using only one one and ground. In the USA, SWER is, as far as I know, against the National Electric Code, although exceptions can (and have been) made. It seems unlikely that SWER is prevalent, though. \$\endgroup\$ – Kevin Keane Apr 8 '15 at 5:21
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I've been reading about this phenomenon after reading your question and the paper you posted . I can't see how that much current could be travelling through ground unless a similar percentage of Minnesota either uses SWER or is wired incorrectly. If that's not the case then the statement must be false.

Claims of current travelling through plumbing is a problem with incorrect wiring for sure. If there is a solid connection from the neutral at the service, to the transformer in the street, to the transformer in substation and back to the plant then it must be lower than 59%. However there is a parallel path through ground rods connected to transformers throughout the grid and at services. I can't see it accounting for such a large percentage of current though.

I measured the resistance between 15 and 25 KOhms through 1 foot of damp soil with my multimeter. (Curiously it was rising steadily like I had my meter on a capacitor and then would drop and restart at different values with no particular pattern). Compared to the resistance of utility wires it is obviously very high.

I have seen (I'm an electrician) a single phase 100a service lose the neutral in the meter socket. The customer called because the screws connecting sections of the baseboard heater (hot water) were glowing red. All of the power being used in the house was travelling through any path to ground it could find.

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I'm not sure that I understand well your question, but the electricity distribution to homes is changed from Delta (triangle) to Y (star) with the neutral to ground.

After the transformer, you can see in every -lets say- 3 stylus a new ground. But if there is a charged ground somewhere (i.e during local thunder storm or lights), the balance in the low voltage transformer disturbed too much. This is a practice in my country.

EDIT

I don't know how your state is consists. May be most is rural area. In any case the problem that you reporting it is complex and have a serious ecological aspect too.

Many questioons arising that can be unswered by an idependent specialized organization. Just a sample:

-How many electricity providers are there?

-Are they using all of them a uniform system or it is a mixed distrribution (SWER etc.)?

-When they update their leaky distribution grid?

-Is farmers or rural areas follow the national codes of electrical installations?

-Are there huge EMF produced by traditional activities like electrical fences etc traveling to gnd?

It is an extremilly serious issue, that needs very-very carefull handling, since an entire state involves.

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  • \$\begingroup\$ I think this answer is only one part of what I'm trying to understand. The statement I'm trying to understand was made about the whole state of Minnesota: 59% of current returns from consumers to substations through the ground, rather than through a neutral wire. I'm sure some distribution lines in Minnesota are three-phase, and some probably are two-wire single-phase, possibly also some single-wire earth return. Your explanation may explain some ground current, but does it explain why 59% of current travels through ground, and only 41% through neutral wires? \$\endgroup\$ – Kevin Keane Apr 7 '15 at 5:51
  • \$\begingroup\$ I was try to read again your recerence, but it is hard to me to understand all aspects because of the language. \$\endgroup\$ – GR Tech Apr 7 '15 at 12:09

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