In the USA, our power companies and electric codes insist on the house feed be in a conduit or cable mounted on the outside surface of the outside wall of the house to the meter and to the "service equipment" (main circuit breaker or fuse). Idea being that it's easier to spot theft of electricity ahead of the meter, and if the feed gets shorted, it won't set the inside of the house on fire.

In my mom's house, we have an underground conduit from the power pole to the basement, where there's the meter and immediately below the meter is a pair of 100A fuses. Less than about 60cm of wires without overcurrent protection (and no wood nearby), code allows about 100cm or so. Then that feeds a heavy BX cable to our circuit breaker panels (wired as subpanels), located in the middle of the house.

By today's American standards, 100A is kinda puny. But it was heavy duty when my father built the house in 1950.

I think we are heading towards that here. I'm an electrician but I've done very little domestic work so I cannot be certain but back when I was working for myself it was legal to run 16mm² single double insulated (SDI) cables from the point of attachment down the wall cavity to the meters.

I am guessing but I think the latest edition of the SAA Wiring Rules (AS/NZS3000) requires the cables to be in a continual conduit though it is still allowed to be in the building cavity.

Because of the 'old way' of doing things, electricity theft is quite common, mainly done to run drug farms and labs. It's not all that uncommon to see on the news someone getting dragged out of their home by the coppers for growing hydroponic marijuana in their home with the use of dozens of 400w metal halide highbay light fittings.

Because our 240v system has an active and neutral wire rather than two actives there is only one service fuse - still called a council fuse by the old school in New South Wales as electricity retailers here used to be split into county councils which were owned and run by local governments until stolen by the state government under its compulsory acquisition reserve powers. Generation was done by the government-owned Electricity Commission until it was split into three seperate corporate entities, still government owned though. Other states had a simpler structure though some have privatised their operations.

Usually, the only time one will see a switchboard inside a residential dwelling is when it is a block of flats and perhaps townhouses. Detached houses will have the council fuse, meter(s) frequency counter for off peak heating and hot water and fuses or circuit breakers for final subcircuits all in the standard meter box at the side of the house.

100A is pretty much all most need here as everything is on 240 volts so the current flow is typically half that found in North America and even Japan, which uses 100 volts. Stove (32A), hot water (20A), pool pump (4A), evaporative air conditioner (3A), two light circuits at 10A each and three power circuits at 16A each is a typical installation these days and 20 points are permitted on each general light and power circuit.

Back in the 1950s here only the kitchen, laundry, dining room, lounge room and perhaps the main bedroom had power points and they were mostly singles. Electrical appliances were limited to a mantel radio in the kitchen, a console radio and heater in the lounge, perhaps a telly after 1956 for those with the affluence for one, washing machine, vacuum cleaner, toaster, fridge and electric jug in the kitchen and optionally a food mixer for the wife to make cakes and bikkies. All that could be sorted with a 40A main service if you had the gas on to cover stove and hot water.

Oddly enough, the Housing Commission had this bad habit of fitting instantaneous electric hot water heaters to their blocks of flats - each flat had one, even if the block had hundreds of flats and these things chew power like there's no tomorrow. These heaters had three elements (one on each phase) at 18A per phase. If everyone in the block was having a shower at the same time you could imagine the load on the substation! To their credit, they equipped flats with gas instantaneous heaters where gas was available. I still remember my grandmother swinging the burner out to light hers when she wanted to wash up the dishes. They weren't automatic back then.

I still remember my grandmother swinging the burner out to light hers when
she wanted to wash up the dishes. They weren't automatic back then.

I had one of those in a place I was renting in the early 70's. I called it the V2 rocket because of the blast that came out the bottom when the main jet lit. Thankfully, it went out with the advent of natural gas.

I also recall those tubular 3 phase instant heaters. I think they were Zip brand.

That's a pretty good summary of house power in the 50s. This topic made me recall my grandfather's house built in the early 1900s. There was hardly a power point to be found. In his garage -- which was a favourite playground of mine as a kid -- I used to find old appliances with bayonet plugs on them (some wooden!) indicating that light sockets were the usual source of power in the early days.

Among that stuff I found a short extension with bayonet plug on one end and standard bakelite GPO socket on the other.

There was also a surprising number of 110v AC things made in the USA, like a motor with a rubber wheel on it for powering a windup gramophone and a 110v shaver. There must have been a stepdown transformer in the mix but I don't recall finding it.

I would have liked to ask him about all of that but he'd had a severe stroke and conversation with him was difficult.

In the 60s there was campaign called "House Power Plus" aimed at getting people to wire their houses for an electric future, and all of the ads featured double GPOs.

Also in the 60s, off peak hot water was all the go with gravity feed tanks in the roof. Ours was switched on and off by ripple current that was audible in the B&W Kriesler TV. Was glad to see that replaced by on-demand mains pressure. I think domestic off peak is a dying breed these days. Don't hear much about it anymore.

Our pair of 100A fuses on our 240VAC centertap grounded system should be equivalent to a signle 100A 240VAC feed in Australia.

Decided to upgrade from the now deleted dangerous method. Installed another in another bedroom, so my 2nd Healing radio has a place to play.
Reason I have 2 of these was that the first one I bought arrived with a broken cabinet, so I got another when it showed up on that auction site. I was able to make a passable repair on the broken cabinet, so at a casual glance it looks fine. Though anyone who knows radios will spot the repairs. Both are electronically restored.

Oh, about 20 years ago we had excessive voltage, 132VAC/264VAC. Too high. Complained to the power company, and it took them a few weeks to track down as to why. Turned out that the distribution network in this town was badly balanced, and they had to switch some parts of town from one phase of the 3 phases to another.

I am taken with the economical use of hardware shown in Wa2ise's opening post on this thread, compared with the "business" referred to by GTC in his post.

Have we something to learn here in Oz, because this "business" seems typical everywhere I have been in Oz? Replacement of street transmission infrastructure currently going on seems to be just replicating the existing hardware, at least in my area of NSW. Maybe it is due to a good supply of cheap hardwood.

One advance is the use in my area of the compact insulators replacing the larger ceramic hardware. Is there an interesting technology story to be told here?

"I am taken with the economical use of hardware shown in Wa2ise's opening post on this thread, compared with the "business" referred to by GTC in his post."

Realize that there are usually 3 to 4 diamond shaped insulators between a pair of power poles. Some are cross shaped.

Older one pictured here (used in pairs to form the diamond shape):


We often mount flags to power poles, as you can see in the top picture.

STC830: I am taken with the economical use of hardware shown in
Wa2ise's opening post on this thread, compared with the "business" referred to
by GTC in his post.

The major difference is that our suburban model is based on low voltage distribution direct to the customer, requiring numerous steps of progressive step down, whereas the American system apparently trunks HV through every street and provides a transformer per customer. Our system certainly makes for some very busy and unsightly poles. No wonder the push for under-grounding in new developments.

As Brad mentioned earlier, the closest we come to the American model is SWER in country areas and therein may be the clue. Perhaps the American distribution system is based historically on very long distances between generators and users, making it economically sensible to stay at HV for as long as possible.

As with many things, I guess we inherited our model from Britain/Europe.

"whereas the American system apparently trunks HV through every street and provides a transformer per customer."

In our USA suburbs, it's about 8 single family houses (customers) per transformer. Depends on the size of the houses, and how packed the neighbourhood is. And there is HV feeding the transformers running down most every street. Mid sized business often have 2 or 3 transformers to themselves (places like Burger Kings (I think the Aussie Burger Kings are called "Hungry Jack") and supermarkets).

^ Okay, so each transformer is capable of supplying around 8 x 2 x 100 amp loads at 240v, or about 400kVA, and each group of 8 separate loads shares the same HV phase.

Looking more closely at your photo, I guess that's a number of LV lines fanning out from below the transformer, and it seems that there is a LV line running to another pole for other residences in that "section"?

I guess those businesses with a three phase requirement get three transformers?

"Okay, so each transformer is capable of supplying around 8 x 2 x 100 amp loads at 240v, or about 400kVA, and each group of 8 separate loads shares the same HV phase"

No, the power company figures that on average each house will not demand all of its rated current. It's more like 10%, on average. That's more like 10amps at 240V per house. And the odds of multiple owners of electric stoves or ovens turning them on at the exact same time are low. The transformer feeding my house is 50KW, if that is what the "50" on it means.

The power company can spot possible overloads by looking at the electric bills of the houses tied to the same transformer, and by waiting for customers to complain about dim lights (sagging voltage). Or when the transformer blows up...

Australian, British and American systems have a lot of similarities. The voltages and hardware are different however the physical distribution methods are similar.

Substations are more common in Australia than most would believe however most new ones are placed underground, along with the 33kV or 11kV feeder cables.

Zone substations are still built on the surface but look more like housing than industrial buildings these days though all new cabling at the supply authority level is now placed underground. Replacement of what is known here as street distributors or put simply, the low voltage (415v/240v) cables is usually a conversion from bare single cables to insulated cluster cables. The advanage with these is that there are fewer supply disruptions due to fallen trees and flying roof iron and fewer electrocuted bats and possums. The downside is that they are more noticable and much more expensive.

Wa2ise's comment about balancing is an interesting one. Here, the SAA Wiring Rules and supply authority service rules dictate that the installing electrician must ensure that all loads are as balanced as possible. In buildings supplied with three phases it is illegal it install a single phase sub-switchboard, it must be a three phase one so that any final sub-circuits can be spread across three phases.

Promised pictures are below. Possibly more to come:-

A fairly new poletop substation, a rare find these days.

An older substation two blocks from the first photo.

One of the more common kiosk substations fed from an underground 11kV service.

Wires in a street I used to live in. Note closeup where the bare conductors connect to cluster cables.

A set of HRC fuses to protect the old poletop substation from overload. These are rated at 400 amps.

A warning to people and possums, with added protection for possums in the form of a slippery surface.

A pole with a 1950's street lamp fitted with an 80 watt mercury vapour lamp, still giving faithful service.

The whole shebang - from top to bottom, 33kV feed from a zone substation, 11kV from a zone substation to the kiosk and poletop substations shown above, 240V service for street lamps (a service no longer provided as street lamps now have their own PE cells), 415/240V three phase cables to supply homes and small businesses, Optus TV cables, Telstra TV cables.

The transformer feeding my house is 50KW, if that is what the "50" on it means.

50 KW seems more reasonable given the size of the unit.

Or when the transformer blows up

Reading that reminded me of something I once heard or read Stephen King say, along the lines of when he was a kid he saw one of those transformers explode into flames, and the image stuck with him, weaving its way into the nature of Carrie.

Zone substations are still built on the surface but look more like housing
than industrial buildings these days

When I was a very young kid, close to where I lived there was a very small open style substation plonked in the corner of a small park with swings in it. I have early recollections of peering through the surrounding chain mesh fence and listening to the hum of the transformer and wondering what it was all about.

The park's still there but the substation is gone. Its footprint was no bigger than a single car garage.

I heard a story not so long ago about a substation near the Walsh Bay piers which was decommissioned and removed when one of the piers was being used as a temporary home for Star City Casino. This substation fed electricity to the piers though one transformer brought 11kV down to 600V DC for Sydney's old tram network.

Believing the substation to be already out of service two apprentices were sent in to start cutting up the copper cabling, probably so it could be flogged to a scrap merchant for some quick cash. As it turned out the substation, every part of it, was alive and one of the workers was killed instantly, the other mentally scarred for life.

I wonder if there are other substations still running redundant equipment. Apart from being deadly, there's an awful lot of power being wasted.

Maybe the difference between the US and Oz systems is the final distribution voltage. The lower current at 240/415 would allow lighter conducters for the same power. In US the higher currrent at 120/240 perhaps makes it more worthwhile to have smaller transformers closer to the consumer.

Here the larger transformers when they fail effect more consumers. When I was a kid on school holidays the lights once went out followed a second later by a boom in the distance. A pole transformer had failed blacking out a number of blocks and setting fire to the pole. Great for the kids - fire brigade followed by a major effort by the county council with several vehicles and a crane to take out the old pole and tranny and put in the new. They must have patched in some power from elsewhere because the power was on that night but the transformer wasn't finally wired in til the next day.

Perhaps the more extreme weather in US - icing, extreme cold etc - make the use of the smaller transformers less disruptive if they fail.