|> | Generally in Australia the system distribution, both the very hi voltage
|> | grid and the local street high voltage is 3 phase DELTA and hence no
|> | neutral.
|> So the single phase pole pigs would have two insulation bushings for the
|> primary connections?
| There are NO single phase pole pigs except the remote SWER installations.
| All street transformers are 3phase 3 wire in 4 wire out. and as far as I can
| find out higher voltage distribution transformers are alwys 3 wire in and 3
| wire out with only relatively light lightining protection wires at the top
| of some tower runs.
Well, that certainly makes it much easier to get three phase service, even
if most homes are only getting one or two phases from that transformer.
But if there was a single phase one, it would have to be the two bushing
type. Suppose you have a neighborhood area, but off to one side of it at
some distance (say 1km) not suitable to run 230 volts directly, is a home
isolated from the others. The closest place to feed it is from the same
distribution going around these neighborhood streets, because that is also
the way the road goes to that house. That distribution is delta, so there
is no neutral handy. So you'd have to run at least two of the distribution
wires out that 1 km road, and put a transformer out there. Would the do
this with three wires and put a three phase transformer, anyway?
|> | There is then a large 40kva or more transformer in the street, sometimes
|> | a pole (outside my house) and sometimes in a box on a pad or hidden in
|> | buildings. These each serve more houses than the typical US pole pig.
|> How many houses can be served by one 40 kVA transformer down under?
| It is hard to tell because the 4 wire 230/400 wireing is often looped with
| more than one transformer connected to a bigger group with hand operated
| disonnects for fault isolation.
So it forms a "networked service".
|> | Gloat (- for USA home workshop people, 3 phase 230/400 volt power is
|> | available anywhere (except at SWER instalations) just for the cost of
|> | installation or sometimes for free. Most ducted Air cons are 3 phase so
|> | of houses already have it installed.
|> Three phase is fine to have around if you don't have the penalty of having
|> and odd voltage. I'm sure nothing for consumers is made designed to be
|> run from 460 volts, so no one would have a reason to get 230/460 volt
|> phase power. The voltages would strictly be 230 and 400 (240 and 415 in
|> legacy installations). In the USA and Canada, many consumer appliances
|> 240 volts single phase. But you don't get that 240 volts where three
|> power is provided in the form of the 120/208 volt system.
| I think I undestand the various voltage problems with three phase and split
| Anything you are likely to buy here is either 1 phase 230v or 3 phase
What if you have a very high power device that can only be run single phase?
Would that not be wired for 400 volts?
| There are some legacy kitchen ovens that were 2 phase.
| Of course it is only a short while since we started to move to 230 from 240
| and some years ago Western Australia was 250.
| My comments about how easy it is to get 3phase were aimed, in jest, at home
| machinists in the US who buy commercial equipment then have to resort to
| some odd convertors to get them to run.
And that is a well aimed jest. It is in fact a real issue. My grandfather
did get 3 phase power for his wood shop, which was in a detached building
on the side of the house distant from where the power came in. This was
done in 1961. My guess is he had assumed the three phase power would be
in the form of "center tapped delta" without him necessarily understanding
the details (he was not an engineer, he was a school teacher of subjects
wood shop and business math). But instead of getting center tapped delta
he apparently got "208Y/120" and wired 3 phases underground to the shop and
just 2 phases into the house. They had the "slow heating" problems with
that lower line-to-line voltage on everything, and it was most problematic
for my grandmother who was always doing cooking for many things. The house
was one of those early "all electric" houses which had no gas service at
all. My grandfather was trying to get the electric issues corrected for
the next 11 years until he passed away. Perhaps the new owners afterwards
would have not needed three phase and single asked for the service to be
reverted to single phase.
I posted a while back a description of the kind of electrical system I would
have used if I could, back in time, have determined what it would be before
all the economics locked us into what we have now. It would have been a
system somewhere beteween what .US and .AU have now. But I would have also
avoided using directly connected line-to-neutral light bulb connections.
The service would have been either 144/288 or 288Y/166 with all utilization
wired line to line. Incandescent lights would have been wired through a
step down transformer to operate at 24 or 12 volts.
OTOH, if the whole world had simply done 400Y/230, fewer issues would exist
today. An electric stove could be wired to 230 volts at just 40 to 60 amps
while if only single ended 120 volts were all that people got in .US then
it would have needed 80 to 120 amps. So we needed that extra split phase
to handle the extra voltage for a few big appliances. The problem comes from
the need to have TWO single phase voltages, which cannot be reproduced using
simple three phase wye/star systems. Eliminating that need solves it.
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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