Safe isolation in the TN-C-S world

[pc1966]

While reading the IET articles there was one on the open PEN risk and now the DNOs are adding another step to "safe isolation" where they clamp the earth bond to check if there is diverted neutral current present before disconnecting anything related to that.

The youtube video for this:

TL;DR Get a clamp ammeter and check ALL cables you plan on disconnecting!

 

[stevethesparks]

Who said a non contact voltage indicator had no use

 

[pc1966]

Who said a non contact voltage indicator had no use

Yes, that was a surprise but equally it makes sense!

Of course it is more one of confirmation of polarity and metalwork being at earth potential, but certainly anything that makes you think "oh, that should not be happening?" is worth having for the rare case you come across a potentially dangerous system to isolate or (possibly worse) a dangerous "dead" system to be connected back up.

 

[stevethesparks]

They can be a very useful tool if used sensibly and nor wholly relied on.
Edit: Only thing is in the video, he didn't prove/test the unit before applying it.

 

[Strima]

Who said a non contact voltage indicator had no use

Part of the process for opening street furniture (G39) is to check using a voltage pen. You can get proving units for them but I use the Martindale TEK200 which has a built in test facility.

 

[loz2754]

Very interesting video. Just added it to my CPD portfolio.

What's that "contact" tester he was using? Never seen one of them before.

Nevermind. Found it. It's a Martindale VT7 single pole contact voltage indicator, 50 to 600 volts. Can be used with PPE gloves.

 

[7029 dave]

Non contact voltage indicator, they have their uses. ?

 

[loz2754]

Non contact voltage indicator, they have their uses. ?

No. Not the non contact one. The other one he used, specifically referred to as a contact voltage indicator. It has a metal tip.

 

[stevethesparks]

He used both ?

 

[loz2754]

He used both ?

Indeed he did. A smaller blue volt stick type, and a larger yellow one with a metal tip. I looked it up and found it on Martindale's website.

 

[timhoward]

Good video - thanks.
And also thanks @loz2754 for identifying that tool. I have one guy who resolutely refuses to chuck his neon screwdriver, and I've just ordered him one of those VT7's so I can personally smash his death-trap up!