Dangerous Practice by Supply Authority

The comment below and in the posts following were provoked by a picture originally posted here:

The occupier of the premises has made it clear that the wires in question were installed by a representative of the Distribution Network Operator, to temporarily power a supply monitor, and on the supply side of the meter for reasons that are obvious given that explanation. No criticism was made nor inferred of the poster or the occupier of the premises.

Ye Gods! I’d condemn that installation straight away :exploding_head:
What’s the (at best) 1.5 mm² wires protected only by the 100 A supply fuse? If that’s not dangerous, I don’t know what is. And whatever is on the end isn’t being charged for the energy extracted.

A bit - as you say on your side of the pond - Heath Robinson. :wink:

Thanks for getting and posting the photo.

And, as Robert has commented, not safe in at least one respect. shocked icon_exclaim

Please note that is my installation and the 1.5 mm2 coming direct from the main fuse is by the Distrubution operator testing why my voltage drops below 210volts.

Please don’t condemn before checking what is actually happening

It would have been nice to have given my permission before my photo was used and this could have been avoided

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Welcome. I think sometimes some people on here could be kinder expressing concerns but it was something people considered potentially lethal and so they spoke out quickly and a bit forcefully. I’m not sure why it’s ok to have near-unfused thin wires even on a temporary measure. But it was criticism of your distribution operator’s work not yours.

While it may have been nicer to get
your agreement, authorisation is not actually normally required when reproducing a picture for commentary. Such use is permitted by law, with a few conditions. This has caused me a few surprises in the past too, so I’m cautious what I post!

Here’s some info and a 30-second video clip on what happens when wires are connected to an overcurrent protection device (circuit breaker) that has a rating greatly exceeding the max current carrying capacity of the wires connected to it.

This is the reason for Robert’s reaction to the picture. Things can go south mighty fast
and the consequences aren’t pretty. We’re NOT trying to twist anyone’s jaws the wrong
way. We simply want folks to understand how dangerous something like this can be.

Some might think that because its “only 240 Volts and single-phase” as well as
“it can’t/won’t happen to me” is truly a false sense of safety.

An electrical explosion, or “arc flash”, occurs when one or more high current arcs are created between energized electrical conductors or between an energized conductor and neutral (ground). Once initiated, the resulting arc(s) can bridge significant distances even though the voltage is relatively low. In the above demonstration, arcs were intentionally initiated by bridging #28 AWG wires across three bus bars in a testing laboratory. When power is applied, the wires immediately explode, forming a conductive plasma which evolve into high-current power arcs between the bus bars. In the above example, three one inch copper bus bars were separated by one inch, and were connected to a 480 volt open circuit source (a large delta-connected distribution transformer). During the 842 millisecond event, the average short circuit current was 17 kiloamperes, and the peak current exceeded 30 kiloamperes. The energy dissipated within a power arc is limited only by the fault current capability of the upstream power source and the duration before protective hardware “clears” (interrupts) the short circuit. In many low voltage (480 - 600 volt) electrical power distribution systems, fault currents can exceed 70,000 amps. The thermal energy liberated within these high-current arcs can be many tens of megawatts - equivalent to several sticks of dynamite. The arc core may reach 35,000 degrees F (four times the surface temperature of the sun!). As the arc “roots” vaporize portions of the copper bus bars, the copper vapor explosively expands to over 60,000 times its solid volume. The incandescent copper vapor rapidly combines with oxygen in the atmosphere, forming dense clouds of cupric oxide, blackening the air and covering nearby objects with black “soot”. Globules of molten copper are also violently ejected, showering the immediate vicinity with 2,000+ degree droplets at speeds that can approach 700 miles per hour.

Magnetic forces also propel the arc along the bus, extending it in the process. The high currents also generate huge magnetic forces that can bend thick bus bars or even rip them from their mountings, possibly creating additional shrapnel. Any unprotected individual unlucky enough to be anywhere near this event would be seriously injured or killed. Because of the extreme danger, most countries now require electrical workers to wear protective clothing and headgear whenever working near energized high-energy equipment.

If the wires are only powering a CT recorder - then I can’t see any good reason not to have connected them in AFTER a suitable fuse in the consumer-unit / fuse-board.

The DNO engineer who did this -should perhaps be formally reported? It is unquestionably dangerous.

It would have been perfectly OK connecting directly to the supplier’s fuse IF the connection was straight into a suitably fault-rated fuse - something a lot less than 60 / 80 /100 A.

I agree it should be reported, the Health & Safety Executive ought to be on the tail of the DNO as well as the individual concerned. He either hadn’t been trained properly, or he disregarded his training through laziness, or his supervisors had pressurised him to the extent where he felt obliged to disregard his and his customer’s safety in order to get the job done fast. None of those are acceptable excuses.

But I disagree with your description

I don’t think a professional engineer would (a) have been sent out to install a monitor on a customer’s premises, and (b) would have bodged a connection like that. They’d have been only too well aware of the consequences had something gone wrong.

Again, assumptions being made that this piece of equipment that you have no photo of is not designed for this.

Regarding powering it, I also thought it would need to take readings at source. Of course it could be battery powered and just be taking readings? The aim was to read every 10 sec to see if it was my equipment or theirs that was faulty.

Put this to bed please.

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I agree that without knowing what is on the end of the wires they’re prejudging the situation somewhat. But I think their point is that unless there is a fuse at the head end of the wires then any problem that results in damage to the wire could potentially cause a very large current to flow. It really doesn’t matter what is on the far end of the wire; the problem is the wire itself.

How likely it is that there could be such damage to a piece of wire I don’t know, but they believe the regs are clear that this wiring is not allowed and is dangerous, and as such somebody operating on behalf of the DNO should never have wired it like this. And they should be reported.

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