Flash Overs

[Wontdothatagain]

If you have ever pulled a servise fuse or think about doing so in the future, STOP and think about this thread.

Untitled

• Wontdothatagain
• 26 May 2013
• 1

Untitled

• Wontdothatagain
• 26 May 2013
• 1

Untitled

• Wontdothatagain
• 26 May 2013
• 1

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[westie101]

The last photo is the most telling, showing the state of some insulated gloves following the failure of a 100A domestic cut-out

 

[Porque223]

There can be quite a bit of energy in an arc flash.
http://ecmweb.com/content/calculating-arc-flash-energy-levels

 

[Wontdothatagain]

There can be quite a bit of energy in an arc flash.
http://ecmweb.com/content/calculating-arc-flash-energy-levels[/QUOTE]

The last time i went for my compentency update, the calculation in that link was used to show some new meter ops the energy that can come out of a service head and it equates to a small car hitting you in the face a 5 MPH

 

[JohnW2]

If you have ever pulled a servise fuse or think about doing so in the future, STOP and think about this thread.

Yes, a salutory reminder. However, is it just me, or is there a 'mismatch' afoot - between theory/sense/rules and practice? Admittedly, I don't recall ever having seen anyone pulling a fuse from a metal cutout, but I've seen it done many times (by DNO or meter people) with plastic ones (most recently 3 or 4 weeks ago) - and there has always been little, if any, PPE used (usually none).

Kind Regards, John

 

[Spark123]

The last photo is the most telling, showing the state of some insulated gloves following the failure of a 100A domestic cut-out

What size fuse feeds a domestic 100A cutout?
I'm thinking that the energy will be a lot greater on the supply side of the 100A fuse and that will depend on external factors such as supply impedance, fuses, transformer size and so on. A fault on the downstream side will be less owing to the 100A fuse let through.

 

[westie101]

What size fuse feeds a domestic 100A cutout?

Anything up to 630A depending on size of transformer and cable, though generally we would use 400A.
Though, of course, there is absolutely no guarantee that one would operate for a fault at a cut-out!

 

[JohnW2]

Anything up to 630A depending on size of transformer and cable, though generally we would use 400A.

Roughly how many domestic installations would that typically supply (per phase)?

Kind Regards, John

 

[Wontdothatagain]

and there has always been little, if any, PPE used (usually none)

And their lies the problem, on the metering side, i could list many factors for not wearing PPE but the most common one is time. More and more companys pay by fit and their seems to be a "throw it on the wall" atitude.

On the DNO side, i must say, almost all wear the PPE.

 

[westie101]

Roughly how many domestic installations would that typically supply (per phase)?

70 to 100

 

[JohnW2]

And their lies the problem, on the metering side, i could list many factors for not wearing PPE but the most common one is time. More and more companys pay by fit and their seems to be a "throw it on the wall" atitude. On the DNO side, i must say, almost all wear the PPE.

I must say that differs from my (albeit very limited) experience - in my experience, the DNO personnel are at least as bad! The case three or four weeks ago (when my daughter's RCD blew up and took out the service fuse, as per the thread here) was certainly a DNO person - and he used absolutely no PPE.

Kind Regards, John

 

[JohnW2]

Roughly how many domestic installations would that typically supply (per phase)?

70 to 100

Thanks. Per phase? Goodness, is the average consumption per installation only 4A-6A at all times of day and in all seasons? ... or do does your design concept allow the fuses to be run for significant periods of time at currents beyond their 'rating'?

Kind Regards, John.

 

[RF Lighting]

I had a DNO bloke out to a failed TN-S a few months back. It was an iron clad cutout, and he pulled the fuse with no PPE at all.

 

[westie101]

Unfortunately in a lot of employment situations staff fail to follow H&S instructions from their employer (in itself an offence under the act)

That does not mean that the risks involved do not exist or that their individual failures can be used as an excuse to "do it yourself"

 

[Wontdothatagain]

I am autided every month by 2 different people, one from my company and another from the company we sub to. They watch you do 1 job and carry out 2 post completes on previous jobs.

The new bloke from the sub company has a little habit of arriving early (all our appointmeents are timed) and parking a ways down the road, he will watch you enter the property and wait 15 minutes and then go in after you and see if you have the PPE with you and the relervent test instruments are being used.

I got a warning last month because i did not have my flame proof overhalls on.