Safe Isolation Procedure

[Steve D]

Hi All,

Over the last few years I've been harping on to my company bosses that we need to wise up with our safe isolation procedure.

The company I work for has approx 100 field service engineers, and in the last couple of weeks our training manager has agreed to purchase approved GS38 voltage indicators and proving units for each engineer.
This is instead of using multimeters to test for dead, as they are currently (although, to be honest, I'd be surprised if as much as half our engineers truly did test for dead before working anyway).

However, the proving unit that has been selected is the cheaper 240V type and not the 690V version.
Our engineers do work on 3ph equipment.

The training manager says that his intention is to test from each line to neutral and each line to earth, to check for dead, instead of also testing between lines.

Now, at college, it was always drummed in to us that safe isolation on a 3ph installation is a 10 point test as you MUST test between lines.

Is there a scenario that might arise where all L-N and L-E show dead but there is still a dangerous voltage between lines ?

I'm not really comfortable agreeing to it as is contradicts everything that I have been taught.

What are your thoughts about it ?

Cheers
Steve

 

[johnboy6083]

voltage is also known as potential difference. So if a phase shorted to your CPC/bonding conductor or neutral or both, and you measured between phase and that, then your meter would read 0v. thats why you test between lines/phases.

 

[ian.settle1]

When I carryout checks to prove that a peice of 3 phase equipment is dead consists of 12 checks

Use proving unit to make sure test lamp is working OK then

L1-L2
L1-L3
L2-L3
L1-N
L2-N
L3-N
L1- EARTH
L2-EARTH
L3- EARTH
N-EARTH

Then check test lamp again with proving ubit

 

[topquark]

You should always test across phases as well as there is a much higher PD across phases ie 400V (sqrt(3)x230).

 

[Guest123]

One of these should be the minimum for 3P confirmation.


Martindale VIPD Voltage Safety Kit - VI13700G and PD690 proving Unit - Voltage Detectors & Proving - Safety Voltage Indicator and Proving Unit VIPD Kit - Test Meters and Electrical Test Equipment Supplier - Test and Measuring Meters

 

[Steve D]

I agree Lenny, I personally have got one of the 690v proving units, however my training manager seems content to give everyone the cheaper 240v proving unit.

 

[JulianC]

You could argue that if your voltage tester is showing the 240v generated by the cheaper proving unit then that's good enough to tell you that your tester will indicate if voltage is present on your system.