I have been reading about SWER and how is used developing countries and Australia outback and is a poor system.
Well I was checking out the transformer on the pole in my back yard and it sure looks like it is hooked up SWER. The poles have 4 wires. 3 off them are the lines to the houses and the 4th is the high voltage. The transformer has 5 wires. The 2 that look like the primary have the high volt on one terminal and a wire coming down the pole to a ground rod the other. The other 3 go to the homes with the center one also connected to the ground. I live in the middle of a city in Ontario. This sure sounds like SWER. Is it?
The primary and secondary share the same grounded conductor. It is not a SWER.
Don
jdevlin,
You're unlikely to have SWER in the middle of Ontario.
SWER systems are really only used where it is un-economic to run more than two wires, and I'm talking way out in the sticks!.
![[Linked Image]](https://www.electrical-contractor.net/ubb/smile.gif)
I read that thread. That is what got me thinking about this.
The primary has only one wire referenced to the ground rod. How is that different SWER just because the secondary is tied to the ground rod also.
One grounded conductor carries both the primary and secondary current. The earth is not being used as a grounded conductor.
Don
Ok I understand that. I was thinking from the primary side. I only have one wire coming in. Doesn't that mean the earth is used as the return to the power plant. That is what I thought SWER was.
The common grounded conductor is connected to a conductor that returns to the power plant. The earth is not being used as a return.
Don
jdevlin
Take a close look at the neutral conductor in the seperate secondary wires that run from pole to pole. When the hot secondary conductors are broken so as not to connect two transformers together, the neutral will be kept continuous.
At each transformer, the secondary neutral will be bonded to the ground wire running down the pole to the butt plate (or ground ball or ground rod) as well as to the transformer can itself. The low side of the primary will be bonded to the inside of the can.
If there's cable TV and/or telephone on these poles, the support messengers for them will also be bonded to the same ground wire.
In my mind, I see the PoCo primary neutral interconnections as being similar to the way the NEC has us hook equipment grounds together out on branch circuits. . .if they are present at a location, they are all connected together. Kinda forms a web.
Don,
Would these be autotransformers?
Redsy,
Just because one point on the primary and secondary are connected to the same conductor does not make this an autotransformer. In an autotransformer connection, the primary and secondary windings are connected in series. Look at
these drawings .
Don
Redsy,
Many older residential sections of a PoCo's distribution grid will have a single Ø of primary high tension line snaking down the alleys for many blocks (one conductor sitting on an insulator right on top of the pole - no cross arm). Each of these lines will carry as many transformers as needed for the installed load in the dwellings and small commercial occupancies along its path. The basic PoCo owned, pole mounted transformer supplying 120/240 1Ø to these buildings has a primary hooked up as one leg of wye. The transformer primary winding has one end connected to the high tension primary line, and the other end connected to a very busy grounded conductor. The secondary center tap is connected to the same grounded conductor.
This transformer is an economical choice as it has only one high voltage insulator leading into its primary winding (cheaper to manufacture), and the line crew only has to mount one cutout to the primary line (less labor).
The turns ratio, for 8 KV to ground, is roughly 33:1, making the return current small by comparison to the secondary neutral currents.
Do, Al,
Thanks for the clarification.
I have occasionally wondered why our local PoCo. systems apparently have only one primary conductor.
The thing that I can't get off my mind, about this setup of common grounded conductors, is this. . .
If I shut off the service disco and pull the meter at my house, and then put a clamp on ammeter on the GEC leading to the metal water service pipe, I will measure current. This will generally be on the order of a few amps. A nice steady background uncancelled alternating magnetic field. Far too many homes have the water service in the front and the electrical in the back, so this magnetic field creating GEC runs right through the house.
Now, admittedly, some of this current is going to be from the collective load unbalance of my neighbors homes and business, but even when they are balanced, the place where my child sleeps is bathed with the field left by the parallel return path for the 8 KV primary current.
I just wish I knew what that means.
Ok I get it now. The neutral I see for the secondary also goes all the way back to the distribution center.
Have any of you gentlemen ever heard of a phenomenon called "stray voltage" or something like that.
Saw an article recently in a local paper; seems some areas of some towns that have had population growth over the years have "ground voltage". Seems like the POCO has "bare" neutrals, and there is leakage thru the earth. The next time the subject hits the papers again, I'll post it.
Any clues???
John
Hotline, most of you probably haven't thought of it, but in my town of about 20k souls, which is fed by a 12.47 kv grounded wye system, the primary neutrals of all the feeders of all the substations are tied together. At every transformer there is what the POCO calls a sectional ground, which is basically a 24 foot deep ground rod. Then on each adjacent pole there is one 8 foot ground rod. Cross country lines are grounded at some set interval that I can't remember right now. In my community this is an area that is roughly 40 square miles. Then there are a couple of 12 kv lines that extend in opposite directions an additional 6 miles or so. It's no wonder "Stray Voltage" exists. Do a google search for it and you will find lots of references. Dairy cows are especially sensitive to low voltages, so most of the better references come from dairy country. When I worked for the POCO no one had ever heard of stray voltage. There was an occasional complaint of being shocked while in the shower, but we were clueless as to the cause or the cure of the problem. Just doesn't happen enough here to be a problem that gets a lot of attention.
Niagara Mohawk has a good site. And
here is a way to lick it.