One of the weirdest happenings electrical, that I have seen, the result of, burning all the way back to a fuse box & stuffed it: Was caused by a single phase welder.

The operation was being done outside an old tin lined shed. When things went awry the ground return ended up going via the tin wall into a venerable metal goose neck light & into its light gauge (correct for job) wire. This fused the earth in the cable from start to finish & wrote it off, naturally its fuse did not let go as its active was not involved. Despite the spectacular results, it did not start a fire.

This was a pre-RCD equipped fuse box, but plastic.

Marc

It's quite common for hard wiring to melt down like that without igniting. Standard TPS cable is rated at 90 degrees. So it'll start to melt after that but definitely before 200 degrees, given the assumption that a rating is about half the tested safe level. So the heat generated to melt the cable insulation isn't always sufficient to ignite timber, dust, etc.

1mm² lighting cable definitely wouldn't cope with the voltage drop from a heavy load like a welder. Whilst a welder can consume less than 10 amps, the constant surge currents will be the culprit.

My conclusion was that due to the fault which appears to have been within the welder, The earth wire ended up being the Neutral / Earth return to the box & it was the shear load that did the damage.

I would have loved to see the Electrical inspectors report on that one. I do think that there had to be issues with the Neutral / Earth of the system for it to need to ground via the gall iron on a wooden framed shed wall and the metal light fitting.

One of the 3 Stooges, as a plumber, confusing a conduit for a water pipe...

Was/is B-grounded delta 3 phase used in Australia?

B-grounded...

Never heard of that.

Connection to transformers and motors can be in a star or delta configuration though and in some cases both. A motor can be started with star connections and then switched after a second or two to delta connections - this lowers the starting surge current consumed by the motor if it is under heavy load. Two popular examples are large air compressors and oil pumps for passenger lifts with hydraulic traction.

I'll note that I've read the editorial for September's Silicon Chip today and there has been quite a response to that of last month.

I believe it's also known as corner-grounded delta:

http://forums.mikeholt.com/attachment.php?attachmentid=7090&stc=1&d=1340927953

Funny thing is I ran into it today and was a bit confused: A rooftop air conditioner on a commercial building that had original 1966 electrical wiring. Its compressor was fed by a 3 pole contactor but its circuit breaker downstairs was 2 pole! Measured 240v across phases and from phases A or C to ground!

Found this about this scheme:
http://static.schneider-electric.us/docs/Circuit%20Protection/Molded%20Case%20Circuit%20Breakers/2700DB0202.pdf.

Thought it would be suitable for Aus because it provides a neutral + same voltage for single & 3 phase.

Ahhh I see. No, I've never seen that here. In Australia, as far as I've seen anyway, we only bond a neutral wire to earth and even then that is only legal (and required) at the main switchboard for an installation. Unbalanced loads are always connected in 'star'. 'Delta' connections are only for balanced loads such as motors and furnaces. As per the diagram in the linked document, balanced delta connections need not have a neutral conductor but none of the actives are ever bonded to earth.

Apropos of the subject, an 11 year old girl in WA is in a coma following contact with a live garden tap:

http://www.abc.net.au/news/2018-03-05/denishar-woods-remains-in-critical-condition-after-electric-sho/9510242

The article mentions recent electrical work having been done in the house. The photo of the tap involved doesn't say much for the plumbing.

I hope the young girl fully recovers.

Any tingle like that could be dangerous.

At my mechanics for a car service and when picking something up off the concrete floor I noticed a tingle. The mechanic eventually got his electrician in for a look and he discovered that the workshop earth rod was corroded.

Yep, any such tingles are not to be ignored/overlooked. They are indicators of a bad situation.

Following on from my post #55, this article contains photos of the supply terminals involved in that case. The incoming neutral looks to be completely cactus, leaving an innocent young girl with severe brain damage:

https://www.abc.net.au/news/2019-09-27/denishar-woods-garden-tap-electrocution-report-released/11553734

That junction box is the one that is installed on the barge boards and eaves of hundreds of thousands of homes around the country. If those screws aren't tight, arcing will heat up the conductors and anneal them, as well as eating part of them away, which in turn increases the arcing. In the middle of winter, having the stove on, cooking tea, whilst the heater is on in the lounge room, enough current will be flowing to get the job done.

Do yourselves a favour - don't use a hose when removing cobwebs from them. They are reasonably weather resistant but not water proof.

A lot has changed here since that was written. In 2013 the replacement house was built here. It became the second building with underground power the studio (1984) having had it re-installed first but with provision for the house. It actually was fed from the previous house.

2016 saw everything put underground. The earth is in wet soil in the cable trenches (old creek bed) and at the time it was installed there were issues getting the job done as the point where the distribution boxes were going was inundated. Originally Neutral was Earth and tied to several metal power poles so there was never an earth issue until in one shed a light had fused neutral to earth & the RCD was never going to be happy with that.

Water pipes were never going to get used for earth as they are all Plastic (miles of it), However, where possible the earth stakes / lines are where the ground is not going to be bone dry. I have as yet not (clamp meter) registered earth current. They damaged the Utility transformer (age not young) seals and after the dirt & oil crept up the EHT insulators (Have photo) and it started to creep past 254V it got replaced.

One should beware that at another place there was a "stick welder" that shorted secondary to ground and burnt out the earth in its lead.
Naturally the fuse /RCD held in as the fault was in the secondary & the primary never over loaded.

There is a comment in the current SC re-tickles. I would note that you can get minor tickles from the old radios with shielded transformers. I had a Kriesler here that I sent out. Where test equipment wasn't happy and it had 55V AC on the chassis measured with a 10M meter. It left with a grounded chassis. Transformer had no earth leakage (I tested it).

With the boxes. They are I assume from looking at the ones I had: designed to have water fall on them from the top not jetted onto them from the bottom. They really should never have been built like that.

I would re-iterate that I wonder how stuff like Leader LSG-11 and a few other transformer fitted things got into the country with metal cases and a cap from mains to chassis (& case) and no mains earth wire? That situation does not last long here.