I got a desperate call this morning from a local childrens nursery - "our heating isnt working, we've had some electrical problem overnight, and now the heating wont come on".
Ok, I dropped my stuff and went straight over, to find the full story.
Eon had just left, there had been a voltage surge, and they had traced the fault not to the local sub-station, or a damaged cable, but to the neutral busbar (more of an Henly block), inside the building, just after the cut-outs, in a TP+N switch.
The 25mm cable had melted the insualtion for around 3 inches, and left a lot of welding style splatters around the henly block. It was all sealed up when I arrived, so I didnt see the damage inside the box.
Onto the heating, luckily, an easy fix, the programmer had blown, so a few wagos linking wires inside the box had the heating on, until a new programmer was fitted later.
Then onto the rest of the building. Virtually everything that was connected to the mains was dead. A few flourescents had survived, and the oven, but 2 freezers, a fridge, 10+ phones, the router and computers, fire alarm, security alarm and many other smaller items were dead.
I reckon £5000 to repair/replace.
Now may be a good time for me to submit a price to fit SPDs.
I asked if they will be claiming on the electricians insurance who did the rewire in July, but, apparently he said he hadnt even opened the main switch box, which I found hard to beleive, but possible I suppose.

Alan.

A good policy is to check and tighten all sub-mains terminals as you go. Sometimes not officially possible if they have been sealed up by the DNO.

Legh

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Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."

If the fault was within a DNO sealed enclosure, then they would be liable for paying the compensation / replacing the failed appliances, just as if the fault was out in the street affecting a larger part of network. I would expect the DNO's representative to examine all the items in the property, then arrange for their replacement.

On the subject of SPDs, I am not sure that you would find SPDs with ratings that were appropriate for protecting against a broken neutral. You could of course use SPDs together with an overvoltage relay and shunt-trip on the main incoming device, but this is not really sensible in most cases.

Regards,

Alan.

Sounds like the single phase kit got the full 400v
when the neutral was lost, as Alan says SPD's won't help in this circumstance.

Regards