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).]
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."
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.
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 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?
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.
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.