I don’t understand this sentence - please can you explain “much greater likelihood”? Greater than what? If the sentence is wrong/misleading/incomplete can you please edit to correct/elaborate preferably by editing your post? If you can revise so I better understand your intention then I’ll edit this post correspondingly.
I came to the reluctant conclusion that using the PAT tester INCREASED the risk of electric shock at a Repair Cafe!
Used without due care and attention, pretty much anything can be dangerous. Apparently many accidents requiring visits to A&E are a result of putting socks on or taking them off.
To be of any value, PAT testing (by which I mean the whole process of checking that mains-powered devices are relatively safe to use) must only be performed by what is termed a “competent” person - i.e. someone who knows what they’re doing, which among many other things includes knowing what the testing device does, how to use it safely (following its instruction manual) and how in general to proceeed safely when mains voltages are involved. I suppose one test of “competence” is whether the person could explain and justify their tests and results in court, should something with legal ramifications happen, and that the court would agree that those are acceptable, so it’s important to note that competence requires taking responsibility for the testing you do.
“Competence” must include discipline in following the instructions for the testing device being used. I use a Kewtech KT71 and the manual has many Caution boxes with instructions like “Do not touch the device under test whilst testing is in progress. Since a high voltage of 500V will be present the user may get an electrical shock” which seems like a pretty clear warning to me, so I try my hardest (it’s me that’s going to get the belt!) to avoid touching at all, or if I have to to hold the earth probe in contact then I avoid touching metal parts of the probe and the thing I’m testing, and to make sure no-one else stands a risk of touching it what I do prior to pushing the Start button is take a moment to stand back and check that there is nothing unintended touching the thing being tested and that there is no risk of anyone close by touching it - it’s good to have the PAT testing taking place in a little space of its own. If I have any doubt I don’t proceed. Mains voltages are dangerous. This sort of thing is also why the only people in the mending area should be those who have to be there because their stuff is being mended or they are in the repair cafe team, and why drinks/food aren’t allowed in the mending area, etc.
Also to put the 500V in context, mains voltage of 240V AC means there are peak voltages of +/-340V-ish (i.e, 680V peak to peak) when mains is connected - not that much different from 500V, so what would be the point of an earth leakage test at e.g. 1.5V or 9V from a multimeter when in real use these high voltages are routinely present? The likelihood of insulation breaking down increases with applied voltage.
We do all this because it’s generally acknowledged that devices which aren’t safety tested can be very dangerous, and importantly many of these risks are avoidable - that’s why PAT testing is often (usually? always?) a pre-requisite of liability insurance: it’s all about avoiding unnecessary risks.
Of course, devices that pass the PAT test can also be dangerous, because mains voltages are dangerous and users don’t necessarily understand what they’re playing with - but rather like our vehicle MOT tests the PAT test gives some basic assurance that the thing isn’t going to kill you or anyone else unless you the user do something slightly stupid or are unlucky.
In my experience, insulation breakdown in an appliance that looks fine on a multimeter but faulty at 500V, whilst not impossible, is extremely rare.
Yes it is very unlikely, but low probability (rareness) is not the same as impossibility or zero potential impact. Lightning does strike, and very occasionally it strikes multiple times. Aeroplane crashes are incredibly rare but I don’t want to be in one and in particular I don’t want to be in one where someone in the chain of command (and not on the plane) has blithely said “pffuh, bureaucratic nonsense that never happens [i.e. it hasn’t happened to us recently] so we don’t need to check it” when the event can in fact happen however unlikely and they could quite easily have checked it in order to avoid unnecessary risks.
If what you’re really saying is that casual non-“competent” use of a PAT testing device is potentially dangerous then I absolutely agree: yes it is, because mains voltages are involved! And that of course means you must make sure it is a “competent” person who takes responsibility for PAT testing. And then also please add that “casual”/“competent” qualifier to what you say and write because it’s important to qualify rather than making sweeping statements. So say instead “I reluctantly came to the conclusion that CASUALLY using a PAT tester INCREASED the risk of electrocution…” For me, that revised phrase really says “I reluctantly came to the conclusion that I wasn’t competent to do PAT testing” which I hope would then be followed by “so I found someone who is competent.”
Or if you have a truly compelling argument and evidence that a PAT testing device increases risks when used correctly in compliance with the instructions for that device by a competent person, then you really should make that argument to the regulatory authorities, or at least to the manufacturer of the device.
For me, performing PAT testing is a pre-requisite for liability insurance, and for helping to ensure electrical safety for mending volunteers - and this doesn’t absolve the volunteers from their responsibility in ensuring they repair safely and that the repair event proceeds safely.