Hi, 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?
Thanks
What makes you think the local HV network is wired in star?
Lots of single phase extensions with only 1 HV fuse and only 1 connection on a HV insulator
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 residence.** I guess there will always be some unbalance current in the neutral but maybe the overall practice of grounding takes care of voltage problems?
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 spans away.
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 thermostat.
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.
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.
-- Ron
Would suburban Montreal count as a remote area?
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 Neutral.
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,
Single wire earth return hv systems were fairly common in the UK a few decades ago, but largly died out with standardisationas did all the non-standard hv voltages.
The OP was suggesting that the transformers in his case are wired star/star.
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 .
That is not abundantly clear from the OP's reply to you.
If
A reference to support your counter assertion?
Bullshit.
Can you kindly explain, then, how the 11kv system is protected against earth faults if the secondary windings of a system transformer are delta connected?
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.)
Has it been fully standardised? We have 11KV /and/ 20KV distribution in this area.
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.
It's 20kv/lv, in parts of the former NEEB area. I gather that it is historical, and as it works well, it wouldn't be cost effective to change it.
Thank you. Just goes to show you're never too old to learn something new! I have little knowledge of the distribution system in that part of the country, my experience wass all down south.
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