Talk of canadian pole pigs reminds me of something strange I saw in Canada
a few years ago and verified again last summer: Some places in central
Canada (I think it was MB or perhaps the contiguous province west of it)
have soil conductivity so high that the local power company uses earth as
the return conductor for AC power distribution!
I was driving down the highway (probably hwy 16) there in 1998 and noticed
only _one_ wire for a HV power distribution system (BIG insulators). I
asked at the next stop about that weirdness and the guy I was talking with
first assured me that it must have been telephone wire because power
systems always use 2 or more llines, but it just so happened that his
friend worked for the power company so he would just call to verify. Well,
his friend confirmed that indeed it was their power distribution system,
and they only needed one conductor because of the extremely high
conductivity of the earth in that area.
We drove through this same area last summer and they are still using only
one conductor. I don't remember the exact area off-hand, but could locate
it on the map if I had to.
I can't help but wonder how efficient that system was.
Jerry W4UK
At 05:53 PM 12/20/2001 -0500, Phil (VA3UX) wrote:
>Not a bad point Jack. Ultimately most of the pigs are removed from the
>can when used for amateur service. I don't know about the standards in the
>US but here in Canada, these pole transformers had to have enough sheet
>insulation between winding layers to meet the electrical requirements
>*before* they were put in oil. The oil then just added a huge additional
>insulation factor as well as providing the required cooling. This came
>from a conversation I had with a design engineer at Ferranti-Packard (at
>one time, one of the largest makers of pole transformers in Canada). So at
>least in Canada, these things can be safely run dry. However the sheet
>insulation is still subject to the same time/temperature/aging effects as
>any other transformer so eventual failure is expected.
>
>Phil
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