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?