Meter Tails Incident

[Sam Ball]

Hi everyone, I am not an electrician and have joined this forum for some help. Here is some background information to my incident:-

Background

House Built 1985
Took ownership December 1999
Electricity meter replaced by electricity supplier 12 January 2004
Consumer unit upgraded 16 January 2008
Current Incident March/April 2017

Incident
During March 2017 I noticed a thud in the lounge on right hand wall and investigated and could not find the cause

The thud or popping sound continued four or five times daily until 2 April 2017 when I investigated further. The electricity meter box was open and I looked inside and noticed the meter tails had a sooty deposit and was arcing.

I contacted my electrician who told me to switch off the power at the consumer unit and he came out immediately and made everything safe.

He noticed that the meter tails were of the wrong size being16.0mm² twin and earth cable old colour conductors of red and black (current rating 70Amps). Possibly original installation as the only work I had done is detailed above.

I agreed that the meter tails be changed to correct specification of 25.0mm² double insulated tails (current rating 110Amps) with 16.0mm² earth (current rating 74Amps).
This work was completed on 4 April 2017

Conclusion

There was an electrical storm early March 2017 and I noticed shortly afterwards that my AV amplifier stopped working due to a short burn fuse blowing. I can only assume that the electrical storm caused a power surge sufficient to not blow the main fuse on the incoming supply at the consumer unit but sufficient to cause heating and arcing of the twin and earth cable which had a current rating of 74Amps.
Is this feasible?

 

[Pete999]

Was the sooty residue at the connections to the meter, which wire was it in your case black or red, if so how far up the wire did the scorching extend? Any idea what size the DNO's fuse is?

 

[Bobster]

Both incidents I'm 99.99% sure have no relevance to each other.

 

[Sam Ball]

Was the sooty residue at the connections to the meter, which wire was it in your case black or red, if so how far up the wire did the scorching extend? Any idea what size the DNO's fuse is?

The sooty residue was not at the meter connections but some 10 inches down from the meter where the red and black wires were arcing/shorting, burning the insulations and sheath. I do not know the DNO fuse but have assumed it to be 100Amp.

 

[Flanders]

As above it sound to me during the meter change or consumer unit upgrade the connections were left loose , which coarse the burning, not the power surge ,The fuse in your amp could of blown for many reasons , the electrical storm being one of them

Edit
OK Sam with that additional information it may not of been a loose connection but a damaged cable

 

[Midwest]

Might have looked like this, if you left them long enough;

 

[HandySparks]

Can you post a photo of the problem cables?

 

[Sam Ball]

Can you post a photo of the problem cables?

No they have been ditched.

 

[Upton Sparks]

Its a loose connection 100%... if it was a lighting strike which filtered into the Electrical system it would do more damage than just blow a fuse in an amplifier and this. also if it was a demand issue i.e you were taking more current than the cable could take, then I would expect to see this thermal damage in more place, along the cable either end of the cable connection at the meter and main switch would be equal susceptible to this damage Live and neutral as well, but if its in one place like this then its a loose connection.

 

[Flanders]

Its a loose connection 100%..

That what I thought but Sam is saying that the damage was 10 inches from the connections , if it was a loose connection the damage would be at the connection ..

 

[Wilko]

Where the 16mm cables were damaged, were they touching each other or anything else? Either they were damaged by heat alone, or had their insulation damaged (by something...) which allowed arcing and further burning damage. Does that fit what you saw? Moral of story - always take a pic

 

[Sam Ball]

Where the 16mm cables were damaged, were they touching each other or anything else? Either they were damaged by heat alone, or had their insulation damaged (by something...) which allowed arcing and further burning damage. Does that fit what you saw? Moral of story - always take a pic

Where the 16mm cables were damaged they were touching each other and glowing red. There was nothing rough enough nearby that could have caused damage to the cables through abrasion.
I was too s**t scared when I saw what was happening that a photo was the last thing on my mind.

 

[davesparks]

Whilst 16mm may be rated at 74Amps it will not overheat and fail at 75Amps, the actual current required to cause this kind of failure would be quite a lot more.
The most likely cause of this is physical damage to the cable, you say the meter cupboard was already open when you got to it, this suggests something has happened to open it.

 

[benji]

Could it have been when the cable was originally stripped the cut was too deep and nicked the inner core insulation

 

[telectrix]

have you noticed the presence of these anywhere round?