An OT question for those west of the pond. I have just been on Holiday
in Montreal and have noticed that the local HV network is wired in Star
and there are many instances of single phase extensions. What happens to
the LV when the HV neutral breaks?
On Jul 2, 12:41 pm, James Salisbury <nntp.dsl.pipex.com> wrote:
That's interesting question! Here, Eastern Canada the 'local' high
voltage is around 13Kv and is 3 wire (3 phase) plus neutral.
Furthermore that neutral is bonded and grounded to everything in sight
including aerial telephone cable messenger support cables, pole guys
etc. The system is called Multi Grounded Neutral. It includes the
neutral on the low 115/230 volt side of the transformers and the house
supply neutral is grounded and bonded (or supposed to be!) at each
I guess there will always be some unbalance current in the neutral but
maybe the overall practice of grounding takes care of voltage
But if neutral were to break!!!!! An affected single phase extension
might suffer a voltage drop? And the two other phases might not? Or
the voltages on the 3 phases might unbalance?
In practice, during the last 39 years living a single phase existence
from one phase of a 3 phase sytem that goes down the opposite side of
the road, we have had no such events. Due to the addition of
additional homes the local distribution has been gradually extended/
improved. Most houses are all electric; this one is now served from a
pole mounted transformer, shared with several other houses, two pole
Despite the sometimes icy winter weather our power is extremely
reliable and restoration always fast. Dedicated line crews work on
aerial plant in even the worst weather. Whereas digging out
underground cables with 30+ inches of frost can often only be done in
daytime and with road closures.
** BTW I guess most know that a standard North American house service
is 3 wire single phase. Comprising Leg A +115 volts, Neutral 0 volts,
and leg B -115 volts.
Lights and outlets are distributed between each leg and neutral.
Heavier appliances (cooking stoves, clothes dryer, hot water tanks and
home heating are supplied by 230v via double pole breakers. All
circuits are radial; haven't seen any ring-main circuits. So the
toaster and the TV etc. are 115 volts, plug in to an outlet and the
hot water tank is permanently wired to 230.
Our electricity is generated almost entirely by hydro power several
hundred miles away, with a Bunker C thermal plant run during the
coldest weather. With a total population of only 500,000 in this whole
province one might expect cost to be high. However for this typical 39
year year old moderately insulated house average cost is 10 cents
(Canadian) per unit. There will be a slight reduction (about 6% this
July) due to lower oil consumption and oil price last winter.
There is no gas except delivered or pick it up yourself propane, which
is expensive. Oil home heating is rapidly falling into disfavour often
being modified by installation of an 'electric furnace'. This house
has individual room electric baseboard heaters. Each room has it's own
Oddly enough although huge amounts of hydro power are generated within
this Canadian province and exported from Labrador to the USA (New York
State) and beyond the island portion of this province is not actually
connected (yet) to the North American grid system! With a major
expansion expected in Labrador, called The Lower Churchill that is
expected to change.
"James Salisbury" <nntp.dsl.pipex.com> wrote in message
I don't know the answer to your question, but perhaps the reason for this
may be to make remote locations more cheaply serviced with a Single Wire
Earth Return ( SWER ) HV supply ? ( ie one conductor on a pole ).
I saw this a lot in Africa ( Namibia, Botswana ) last year.
"James Salisbury" <nntp.dsl.pipex.com> wrote in message
Not in itself, but perhaps there are remoteish areas served from there.
It's a big ole place, and you don't need to travel far from the cities to
find yourself in the wilds.
I don't know Montreal area at all myself, tho.
It was just a thought as to why the HV network may be configured with a
On Fri, 03 Jul 2009 19:31:33 +0100, email@example.com wrote:
Sure it's not 22kv? I'm aware of some 22kv, but it's generally part of the
sub-transmission network, most of which is 33kv, and which goes up to
132kv. Transmission these days is 275 and 400kv. I'm also aware of 33kv/lv
transformers in isolated places where there's no 11kv in the vicinity, but
generally ehv to lv transformers are quite uncommon.
On Thu, 02 Jul 2009 15:41:12 +0100, James Salisbury wrote:
No different to this country. All system transformers are wired delta/star,
with the star point being connected to earth through a liquid resistance to
limit fault current. How else could the system be protected against earth
faults if there were no connection to earth?
There is no neutral conductor on the 11kv system. I'm guessing you saw an
aerial earthwire. Normally only used in the country on tower lines,
Computers are incredibly fast, accurate, and stupid;
On Fri, 03 Jul 2009 10:30:00 +0100, Dave Osborne wrote:
I don't think so, BICBW. It's unlikely he'd have found out how the
transformers were wound. You trimmed off the bit of my previous post that
might have answered his query if he was basing his comments purely on the
number of wires he was seing.
OK, I'll bite. You apparently didn't read the OP's answer to my original
question which was "What makes you think HV network is wired in star?"
to which the OP replied "Lots of single phase extensions with only 1 HV
fuse and only 1 connection on a HV insulator"
Therefore, presumably there *is* an HV neutral on the OP's system. If
some of the HV network in Canada is wired star, then some of the network
transformers would be delta/delta and some would be delta/star and some
would be star/star.
Your assertion that "all system transformers are wired delta/star" is
untrue anyway. Pretty much all EHV/HV, HV/HV, HV/MV transformers in the
UK are wired delta/delta. In general, only final MV/LV substation
transformers are wired delta/star .
On Fri, 03 Jul 2009 14:50:34 +0100, Dave Osborne wrote:
That is not abundantly clear from the OP's reply to you.
A reference to support your counter assertion?
Can you kindly explain, then, how the 11kv system is protected against
earth faults if the secondary windings of a system transformer are delta
I suggest you stop now, before you dig yourself into an even bigger hole.
(Hint: I know what I'm talking about, you don't.)
Whenever I look for something, it's always in the last place I look.
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