smart meter installer ppe

[stuartR1963]

Hi all, I just had a smart meter fitted and the guy who installed it wore insulated gloves and a full face shield, this might be daft but what would happen if he had shorted out the cut out fuse? Is he likely to blow a fuse in the substation or will it just arc and bang out of control? would the installer likely be okay? The reason I asked is I stupidly cut an extension lead cable not too long ago which resulted in a loud bang, very bright flash and a spray of molten copper (no exageration) I am a bit concerned about the face shield ppe, would the flash from the short circuit not cause blindness, it nearly blinded me, it may protect molten copper spraying on your face but will it protect against the flash? the face shield was just clear see through plastic.
thanks.

 

[securespark]

https://www.substation-safety.com/product/sofamel-sp-182-face-shield/

 

[stuartR1963]

Thanks, I wasn't aware of that feature with the face shield, out of interest when you short out the mains in your house is the short circuit flash and bang the full force from the substation? or is the short circuit impact limited by the mcbs in the consumer unit? would shorting the cut out fuse be much worse, or will the flash and bang be the same or will it be much louder and brighter and keep going until something melts?,would shorting out the main fuse or service cable likely blow a fuse back at the substation?, the substation is about 100 meters away from my house, sorry if these are weird questions i'm just interested. thanks

 

[plugwash]

There are two questions really, how big is the initial current and how long does it last.

The initial current in a short at the incoming position of a domestic installation will likely be somewhere from high hundreds to low thousands of amps. As you move further into the installation the short circuit current will reduce because of the resistance of the cables.

The big thing with working around the service cutout though is how long the fault can last. A fault in your installation will likely be quickly disconnected by a fuse or breaker but if there is a short before the fuse in the service cutout (happens occasionally) it has to blow a much higher-rated fuse. This can take a long time or even not happen at all.

 

[Adam_151]

would shorting the cut out fuse be much worse

Yes

,would shorting out the main fuse or service cable likely blow a fuse back at the substation?

A fault downstream of the service fuse would take the servcie fuse out, a fault before it is likely to blow itself clear before the upstream protection opens.

Link here you might find usful: https://www.geindustrial.com/sites/...c-Flash-Article_GE_Industrial_Solutions_0.pdf Its amercian, and while national standards and system designs vary a bit...Physics doesn't recognise national borders

You have to look at the other side of risk assessment as well, you are asking "how bad is the bang likely to be", the other side is is "how likely is it to go bang?". For a henley series 7 100A SPN cutout, most unlikely, older metal cased equipment might have a higher probably, if for example the fuse carrier has welded its self into the switchgear then attempts to remove ti might instead break the porceilin insulator that hold the fuse contacts off the metal case..

Interestingly enough, if the supply board think the cutout is in a poor condition and there is a risk of this happening, they sometimes isolate by digging down, opening and cutting the servcie cable, then changing the cutout and jointing it back together, with the correct procedures, the live jointing operation is far safer than touching a suspect cutout

 

[winston1]

Hi all, I just had a smart meter fitted

Let's hope you won't regret that when they start charging you a higher rate at peak times.

Did they tell you you will save money? You won't unless they reduce your unit rate, (they won't). They may tell you that now you can see what you are using more easily you will cut down. You might for 3 weeks, than realise you are miserable with less heating or TV. Then there is the additional, all be it small, cost of batteries for the remote unit.

 

[SimonH2]

You may think that the low voltage won't give too much of a spark - but given a low enough impedance and a trigger it sure as heck can maintain a plasma arc. OK this one is 480V - but it demonstrates just what can happen.
http://www.capturedlightning.com/frames/longarc.htm#480_volt_arc_flash
In practice, the distance between the cores (electrodes of the arc) in your supply cable will be considerably less than in this video, meaning a much shorter arc and hence less voltage required to maintain it. As to whether the substation fuses blow (and how long they take) depends on the impedance of your supply and the fuse rating - so impossible to say. So the fuses may blow quickly, they may blow after a bit of a delay long enough to spray a bit of molten copper around your house, or they might not blow for some time while your supply cable burns like a roman candle. In any case, you don't want to be in the way of the spray - just a bit of welding spatter is enough to tell me that

Then read this and see if you still think PPE is "over-reated" - it makes rather disturbing reading at times, and should rpobably be required reading for everyone involed with electrics.
https://miningquiz.com/pdf/Electrical/Electrical_accident.pdf

Having said that, when we had an isolator installed, there was no PPE to be seen

 

[ericmark]

It is ionization of the atmosphere we worry about. Luck it does no happen very often however when it does happen there is a big bang.

It also happened with the humble light bulb, when they failed most just go out, but every so often it has a large flash as it fails, the internal fuse blows and no harm but when a MCB is used these often trip first.