ECN Forum Forums Technical Discussion Electrical Theory and Applications Voltage Gradient

"...single HV line with a return path by just a local ground rod." 'Earth return' has been done in southern Alberta at 14.4kV to rural homes. It's quite odd to see the first time.

Bjarney;
would'nt this be a somewhat inefficent circuit, given earth impedance

sparky, it's for real. I found a few comments about it...a bit unusal. Don't know if it's used in the US.

“The Single Wire Earth Return (SWER) system was developed to achieve minimum cost in supplying widely dispersed rural customers, and is used in most States [of Australia.]”
http://www.worldaware.org.uk/awards/awards1997/gibb.html http://www.ctech.ac.za/conf/due/2001/abstracts/ab13.html

Regarding hobby flying in Australia: “The SWERs do not run along roads but cut through farm land and are not easy to see from the air. They consist of a single wire strung from the tops of pencil poles. The wires are high tensile strength steel. The poles are needed only every 500 feet, not the 200 feet we see in the US.”

Gives a new meaning to giving someone a hot foot!

It would be interesting to know what precautions they will be taking in Africa to keep people and animals away from any potential (excuse the pun) voltage gradient area around the rod.

Barrier? Fences?

In southern Alberta, Canada, SWER was observed at probably a dozen or two farmhouses. At each transformer the one visible “safety feature” was two driven rods—one at the transformer pole and one at the second pole out. For each transformer there was one lower neutral span between the first and second poles for interconnecting the two rods. They utility was required to conduct periodic ground-resistance testing by governmental mandate.

Each 14.4kV-primary transformer was limited to something like 15kVA, making the hi-side ground current a bit above 1 ampere at full secondary load. I’m sure earthworms considered it their version of The Vulcan Death Ray. In maybe 50 miles of road, I noticed only one ‘open-wye-primary’ transformer bank, to serve what appeared to be a small-town water pump. {This was couple of decades ago.}


[This message has been edited by Bjarney (edited 05-22-2002).]

Vulcan Death Ray Hehe... Conjures up memories of watching the old 1930s "Flash Gordon" serial on children's TV during the school holidays!

Leaving aside SWER, just how common are single-phase xfmrs fed line-to-neutral? I've never been on the HV distribution side of things here (except a local site system), but I've never seen anything other than 3w delta with single-ph xfmrs run phase-to-phase.

The majority of the utility transformers that serve single family houses in this area are single pahse line to neutral, with a common primary/secondary neutral.
Don(resqcapt19)

Bjarney,
this SWER is giving me a real short circuit, what say we move it a tad mainsteam???

One more way-off-topic post and then I'll quit. pauluk— phase-to-phase versus phase-to-neutral primary transformer connections in the US are a regional thing, and often passionately defended on local turf. Overhead or underground, the choices are the same. Within a mile of my house is ~ten 1ø ø-ø, [12,470V…and two primary fused cutouts] one 1ø ø-n, [7200V—probably a 50-year-old installation…one primary fused cutout] 3ø delta-primary dairy and <150Hp irrigation pumps, but also a new ~25-unit housing tract fed full 3ø underground from 3ø4W overhead […all with 3 primary fused cutouts.] One older ungrounded-wye-primary bank to a ~40Hp pump was recently retired. But also, I don’t think a homeowner could get 3ø residential service in the same development at any price. The subsurface 1ø transformers there are served ‘staggered’ ø-ø; probably 3-4 homes per transformer. In most cases, phase-to-phase powered 1ø transformers have better voltage regulation than otherwise equal ø-n versions, but are probably somewhat more expensive to install and maintain.

There are a lot of reasons for either, and in 3ø arrangements they manifest as delta-primary and wye-primary connections. Your favorite open-delta service can even be fed as open-delta or open-wye on bank primaries.

I understand that 3ø servce [208Y/120] in larger homes is common—as larger houses go, but usually billed at commercial power rates. (If you’ve got enough the money for a home, power cost isn’t a make-or-break decision.) There are cases of homes having indoor atriums cooled by 60-ton water chillers…i.e., with ~60Hp motors.

"America -- Land of contrasts." Also applies to power distribution systems!

Many thanks for putting up with my questions on this, but I thought it was about time I investigated the HV distribution a little more deeply.

Steve,
Sorry for unintentionally hijacking your thread. Didn't mean to, but one thing just seems to lead to another.