50 volt can still make you jump. But in the main I work with just the single pole switching RCBO turned off, with of course the clip and lock so can't be switched on, and always test for voltage and current before working on the device, I don't use a proving unit, I know I should, but I am a bit lazy, and in my own house don't bother locking off, as no one is going to switch back on.
The biggest risk is likely the borrowed neutral, I hope my clamp on which will measure down to 0.001 amp will alert me, and it also has NCV sensor so even without a reference point I should detect and live wires, I don't know how the NCV works, but it beeps, flashes a red indicator light, and shows 1 to 4 bars on the display, so not a simple reed switch.
I know many feel the NCV testers should be thrown in the bin, but I feel there are very good as a secondary test. Opps sorry NCV = non contact voltage.
But it can miss-lead
seen here showing all 4 bars, when put next to a USB charger which should be 5 volt, so it should not have shown any AC voltage, tried 3 power supplies, including the lap top, if I unplugged the lap top charger it stopped, but can't see three independent devices all being faulty, however showing voltage when there is not is better than not showing when there is. No voltage it displays EF.
I always check now since in the late 70's I went to remove a socket which was halfway up a wall, house not occupied so no point removing fuses, I simply turned off main isolator, lucky I was using a neon screwdriver, which alerted me it was live, found it was tapped into next doors supply, houses stepped up the hill which was why half way up the wall, owner of the highest house had left keys with neighbour while on holiday, and he had drilled a hole back of neighbours socket and put his socket where the wires came through, there had been a number of people in the lower house, so no idea when or who did it.
