Backup down under

[wattmatters]

In a 3phase configuration you should have 5 conductors entering from the main. 4 current carrying conductors including the neutral and the grounding conductor. Is that correct?

No, 4 wires. 3 lines with a common neutral. I get 4 wires fed from the pole just like a, b, c, d on the right of this diagram:

https://electrical-engineering-portal.com/current-systems-voltage-levels#lv-three-phase-4-wire-system

 

[Ozark Tinkering]

Correct with an apology and wording correction. Count the wires in your diagram again from the secondary side of that utility transformer. That's a center tapped Y secondary configuration of a delta wye utility transformer and they bring 4 current carrying conductors down from the pole to your service head. You also have to count that ground you see. It's established at the service ground. That's a total of 5 wires that must be carried to any sub-panel as in my original statement minus a key word.
Let's put my statement in context with the conversation you and I were having. That's my fault and I left out one word (panel) that it wasn't taken in context because I ramble on about stuff unrelated to the subject so before I digress further...it took some effort to figure out why I said it that when it was presented back to me "stand alone".
So if I add panel to my statement it would read;
"In a 3phase configuration you should have 5 conductors entering from the main panel. 4 current carrying conductors including the neutral and the grounding conductor. Is that correct?"

Does that change your answer?

I do note that both our outbuildings, which each have sub boards, have their own local ground post. The sub boards would have a ground wire connected back to the main panel (part of the 3-phase supply cable). So I guess they would be classed as supplemental grounds in your terminology.

In a 3phase configuration you should have 5 conductors entering from the main. 4 current carrying conductors including the neutral and the grounding conductor. Is that correct?

No, 4 wires. 3 lines with a common neutral. I get 4 wires fed from the pole just like a, b, c, d on the right of this diagram:

View attachment 82043

https://electrical-engineering-portal.com/current-systems-voltage-levels#lv-three-phase-4-wire-system

 

[wattmatters]

Does that change your answer?

Some photos might help.

Here is the power pole:





4 wires only connected to home main panel:



The house's main panel has an earth (connected to a copper water pipe - they did that back in the '70s), while the two sub panels for the granny flat (the building you can part see in the power pole pic) and the mancave each also have their own earth rods.

I'm not clear however about the relationship between the individual panel earths and the neutral. It's all been done by licensed electricians so I can only presume it meets our code.

When it's appropriate I'll have a peek behind the panel to see what I can see. It's a bit of a bugger to pull out, there's a LOT going on with my panel and I prefer to not be moving it often.

The main feed appears to be 16mm² cable based on what's connected to the main links.

 

[Ozark Tinkering]

That would be an illegal installation in the US. A licensed electrician would risk his license if he did that, if he were making that installation in today's world. Anything installed prior to 2008 NEC changes were grandfathered. But the changes were made for safety reasons.

A significant change occurred in the 2008 National Electrical Code ( NEC) at Section 250.32 (B) pertaining to the acceptable grounding methods at buildings or structures supplied by a feeder or branch circuits from a grounded service located at another building or structure supplied from a common service.


Edited

 

[Ozark Tinkering]

That would be an illegal installation in the US. A licensed electrician would risk his license if he did that if he were making that installation in today's world. Anything installed prior to 2008 NEC changes were grandfathered. But the changes were made for safety reasons.

A significant change occurred in the 2008 National Electrical Code ( NEC) at Section 250.32 (B) pertaining to the acceptable grounding methods at buildings or structures supplied by a feeder or branch circuits from a grounded service located at another building or structure supplied from a common service.


Edited

Maybe think of it this way;
Would you feel safe out in the yard using an un-grounded extension cord on your weed eater that has a metal handle while standing in damp grass? Do you want to be the path of least resistance?

 

[wattmatters]

Would you feel safe out in the yard using an un-grounded extension cord on your weed eater that has a metal handle while standing in damp grass?

With many acres of land to cover, all yard equipment is self powered.

There's no such thing as an ungrounded extension cord here. All regular extension cords include a ground pin and all our power outlets have a ground socket (all 3-pin outlets).

But yes some appliances have plugs which don't use the ground pin, just the active and neutral. These would be double insulated to A/NZ electrical standards. Probably the only item I occasionally use which plugs in for outdoor use would be the pressure washer. It would be a typical double insulated device. Touch points are all plastic anyway.

 

[Ozark Tinkering]

With many acres of land to cover, all yard equipment is self powered.

There's no such thing as an ungrounded extension cord here. All regular extension cords include a ground pin and all our power outlets have a ground socket (all 3-pin outlets).

But yes some appliances have plugs which don't use the ground pin, just the active and neutral. These would be double insulated to A/NZ electrical standards. Probably the only item I occasionally use which plugs in for outdoor use would be the pressure washer. It would be a typical double insulated device. Touch points are all plastic anyway.

The point has always been that your outbuildings are effectively being powered by un-grounded 3-phase extension cords and rely instead on whatever other least path of resistance it finds to ground, making it less safe. That condition exists all over the planet including here in Arkansas and everyone is grandfathered in the US if it was installed prior to '08. That doesn't change how it affects safety. We investigated an electricution death once involving that same issue and that's what drove it home to me. Everyone can choose for themselves of course. I know just about all the tools sold today are either double insulated or are battery run and that further obscures best practice to the casual observer/user. again the point remains.
You've got a really nice place there. Wifey's packed and been waiting in the truck to leave for the boat for 3 days now.

 

[Ozark Tinkering]

Here is the configuration that my utility provides. Follow the grounding in the illustration. Look and see that the neutral is grounded at the transformer and then feeds out to the customer service? That ground is strictly to protect the utility transformer and the service cable feeding your service. The service cable has no other protection than the 7200volt fuse on the primary side of the transformer. When it enters the main panel it is immediately grounded again to establish YOUR service. One place and one place only. Otherwise it has to choose which ground no matter how far away, is easy the path.

 

[Hedges]

An all-pole GFCI would be a nice thing to use.
Since both Neutral and Ground come from power pole on a single wire, if that opens then neutral downstream becomes hot. We have those for portable use, since can't be sure the outlet we plug into isn't wired backward.

Trouble is, your Ground also becomes hot, so I'm not sure what to do about that.
Your main panel having ground to copper water pipe may help, but not guaranteed. If you're holding the handle of a grounded metal tool and standing on the dirt, ideally tool and dirt are at the same potential. But not guaranteed; there will be a "step potential" between different locations of the earth, due to ground rod at house being driven to perhaps 240V relative to ground rod at power pole. That would be avoided if only a single ground location, at your panel. When several houses are fed by one transformer and each has its own ground rod, the issue would still be present.

Does anybody make, and would it be proper to have, an all-pole GFCI that disconnects ground of a socket as well?
Disconnecting ground probably wouldn't be considered proper, so let's say a spring loaded device to yank extension cord from outlet if power of outlet goes out. (Because that would be the proper approach to rescuing someone experiencing a shock from a tool on an extension cord. In fact, that was demonstrated in a safety video I saw for class yesterday.)

By the way, since you have 3-phase, be aware of "arc flash" (another topic of our training).
It was said this is only a problem for multiple phase power. I think because single phase has a zero crossing which will extinguish arc in 1/2 cycle. With 3 phase, the plasma of arc can be kept alive by each phase in turn, because one always has voltage. Until the sustained arc goes out by breaker tripping, you're exposed to extreme heat and UV. Magnitude of current depends on resistance of transformer and wires (voltage droop under load would indicate what short-circuit current is available.)

 

[Ozark Tinkering]

I should have looked closer at what I was asking you to look close at... Homes with copper plumbing have the cold water side bonded to ground for safety reasons. My home doesn't have a copper water line and we use an 8' copper clad ground rod here. A ufer ground is also acceptable. So for the diagram I provided delete the cold water ground. It's just about a given here to bond the cold water line on commercial buildings

 

[Ozark Tinkering]

By the way, since you have 3-phase, be aware of "arc flash" (another topic of our training).

I don't have 3-phase at my house. Look at the diagram. It's single split phase on the secondary.
I had NFPA 70E arc flash training. I did hv splicing and terminations up to 15kv and still wear flame retardant shirts.

 

[wattmatters]

Here is the configuration that my utility provides.

I find that diagram confusing. Seems to me there is a ground both at the consumer side of the transformer and another at the home's distribution panel. What exactly is different to what I have then?

Note my local transformer is 380m line distance away and services other properties.

 

[Ozark Tinkering]

I find that diagram confusing. Seems to me there is a ground both at the consumer side of the transformer and another at the home's distribution panel. What exactly is different to what I have then?

Note my local transformer is 380m line distance away and services other properties.

That's what I was trying to tell you...

Follow the grounding in the illustration. Look and see that the neutral is grounded at the transformer and then feeds out to the customer service? That ground is strictly to protect the utility transformer and the service cable feeding your service. The service cable has no other protection than the 7200volt fuse on the primary side of the transformer. When it enters the main panel it is immediately grounded again to establish YOUR service. One place and one place only. Otherwise it has to choose which ground no matter how far away, is easy the path.

They don't want a fault on your end over-loadning their line and transformer. Remember the neutral is not fused at your service so that would mean lots of amps are possible back to neutral/ground whever it is established. My fire stops at my service disconnect. Your fire goes back and burns that pole down.

 

[Hedges]

I don't have 3-phase at my house. Look at the diagram. It's single split phase on the secondary.
I had NFPA 70E arc flash training. I did hv splicing and terminations up to 15kv and still wear flame retardant shirts.

Mine is about same as yours. Ground rod at house, don't know if neutral also grounded at underground transformer (shared with several neighbors, and I also don't know if we each have separate windings or are electrically connected. Spring loaded terminals connect each wire. Utility had to replace it in the past year.

Wattmatters, though. He has 240/415V "Y"
That could get into the arc flash/blast hazard range when working on a panel.
From the tables in the class I just took, could require category 2 protection (up to 8 cal/cm^2 exposure).
Making sure nothing is live of course is the thing to do. Our OSHA/NFPA standards call for wearing the garb while testing to ensure no voltage.

I don't have any such gear. Almost all work on 120/240V split-phase. A little bit of 230V single phase or two legs of 208V at work.
Once did job that included relocating a transformer, 480V to 120/208Y.
That's the only higher current stuff. Occasionally high voltage supplies, little to no current.

 

[Quattrohead]

The USA split phase is totally different from anything else in the world, don't be getting yourselves all confused about how everyone else does it.
The UK and Austrailia are similar in that everything is either earthed or double insulated. However I did not know that 3 phase is common in Austrailia. Makes sense because the distances are further ???

 

[Ozark Tinkering]

Mine is about same as yours. Ground rod at house, don't know if neutral also grounded at underground transformer (shared with several neighbors, and I also don't know if we each have separate windings or are electrically connected. Spring loaded terminals connect each wire. Utility had to replace it in the past year.

Wattmatters, though. He has 240/415V "Y"
That could get into the arc flash/blast hazard range when working on a panel.
From the tables in the class I just took, could require category 2 protection (up to 8 cal/cm^2 exposure).
Making sure nothing is live of course is the thing to do. Our OSHA/NFPA standards call for wearing the garb while testing to ensure no voltage.

I don't have any such gear. Almost all work on 120/240V split-phase. A little bit of 230V single phase or two legs of 208V at work.
Once did job that included relocating a transformer, 480V to 120/208Y.
That's the only higher current stuff. Occasionally high voltage supplies, little to no current.

I removed the cover from a live 3-phase 480volt 250amp panel in a factory back in '94 that made aluminum injection molded bbq grills. Part of the process involved finish grinding. Aluminum grindings had collected in the conduit that fed into the top of the panel. When I lifted off the cover, the dust fell down and created a white fireball between the 3 terminated feeders 2' in front of my face. It blew me off my feet and unconscious. When I regained came to I was temporarily blinded and apparently my face was smoking and most of my beard was gone. A crowd of workers had gathered around me thinking I was dead. My glass saved my eyeballs. My nose looked like a sausage left on the grill too long. That's my personal up close experience with 3-phase arc flash and I've seen worse.
It wasn't until '07 we got the NFPA 70E certification and flame retardant shirt. By then you'd never know I had over cooked my beak.

 

[curiouscarbon]

glad yer beak is doing better these days ?

 

[wattmatters]

In any case, there's not a lot I can do.

Off my own bat I had the main circuit board upgraded to current standards right after we moved here in 2016. It was full of the old ceramic based wire fuses, with not a breaker in sight, well except for this old switch which looked like bakelight although don't quote me on that. Surely they were not still being used in the 1970s?

And again in 2018 whatever upgrade standards were required were again met when the grid-tied solar PV was installed (required to gain approval for installation), and then again at start of 2020 when the granny flat was connected the local power distribution company made it clear what changes the sparky needed to make.

 

[wattmatters]

Reading a bit more and learning as I go, I went through this wiki reference (not that it will necessarily be correct, it was at least a place to start).

Earthing system - Wikipedia

en.wikipedia.org

If I am reading it right, while the earthing system now used here is the TT-C-S earthing system, mine would appear to be a TT earthing set up.

Looking at some other references, e.g.:

Getting down to earth: Earthing explained - GSES

In an electrical network, an earthing system is a safety measure which protects human life and electrical equipment. As earthing systems differ from country to country, it is important to have a good understanding of the different types of earthing systems as the global PV installed capacity...

www.gses.com.au

They state:

With a TT configuration, consumers employ their own earth connection within the premises, which is independent of any earth connection on the source side. This type of earthing is typically used in situations where a distribution network service provider (DNSP) cannot guarantee a low-voltage connection back to the power supply. TT earthing was common in Australia prior to 1980 and is still used in some parts of the country.

With the TT earthing systems, an RCD is needed on all AC power circuits for suitable protection.

As per IEC 60364-4-41, all the exposed conductive parts that are collectively protected by the same protective device shall be connected by the protective conductors to an earth electrode common to all those parts.

Our place was built early/mid 1970s.

This is the accompanying diagram, and this looks like what I have (except I have 3 x L, not 1 x L).

So it seems this is still an earthing option used here in some places, and it may be due to our location (rural). I note this statement in the above wiki item:

TT networks do not pose any serious risks in the case of a broken neutral. In addition, in locations where power is distributed overhead, earth conductors are not at risk of becoming live should any overhead distribution conductor be fractured by, say, a fallen tree or branch.

Fallen trees are a common issue for our rural networks. The distribution company spends a lot of time/money on powerline surveillance and pruning or removing trees considered to be a threat but they can't do them all and fallen trees (usually storm related) is our main cause of grid outages. Every so often their helicopters are out doing line surveys around the district. They have 189,000km of powerlines with 163,000km of that in bushfire zones, and ~1.4M power poles.

Our upgraded boards have RCDs on every circuit.

 

[Ozark Tinkering]

In any case, there's not a lot I can do.

That's the bottom line.
It's interesting how different enforcement jurisdictions around the world have developed their own "best practice" in construction and use of utility power. Most of the world population has had practical use of electricity for less than 100 years and much of the regulation we place on techniques is based on observations made over time as different scenarios take place and we try to adjust our own behavior around a natural phenomenon we can't see and is not only deadly to the touch but if angered can reach out and touch.
As each of our tribes developed means to make use of this unseen power we cunningly figured out different ways to avoid its deadly touch and expand its use to all our people.
The National Electric Code is only one of many different rule books on best practice electrical installations that has been developed over 125 years. It's America's version. The 1st edition in 1897 was only 58 pages. We didn't know much back then and rules were simple based a lot on the last worker to get blown up. The Lineman Henry Miller, considered to be the father of the International Brotherhood of Electrical Workers died from electrocution in Washington D.C. just the year before, in 1896. Tesla and Edison were about to go enter an epic battle over AC vs. DC distribution while electrical workers were being killed at an unsustainable rate.
Egos clashed.
At the same time in history Europe and the UK were doing their own thing as we all figured out how we might harness its awesome power.
Flash forward 125 years and now the world is interconnected to the point I can type this thought on a keyboard in the middle of North America and in an instant it appers on your monitor somewhere in Australia halfway across the world and not only that but it appears on 100s of monitors around the globe of other active users at the same time.
For the first time in history we are each able to examine and discuss the differences and reasons why each of our cultures systems evolved the way they have. I believe that much like the way the NEC has continued to evolve over time, every other jurisdictional authority is doing the same.
Now we can look around and see that none of us have all the answers and the truth seems to be a moving target.
What voltage your utility provides you and the means and methods they decide to employ when providing their product is up to the local authority, who base their rules on past practice results of the original provider and dead people. Egos persist.
I think where we are now is our ability to communicate has outpaced our understanding. Most of us including myself, base our own best practice on the developed best practice in our own neighborhood since the early days.
If your provider doesn't care that their wire is carrying the imbalance in your system then they have probably calculated the risk to their wire as being worth exercising Grandpa's Right and leaving it as is.
I think this is the first forum I've been on where I can discuss the differences in how rules are made and implemented around the world. It used to be we only had to argue between the 50 states in the U.S. and even then some differences are stark.