cyrano.mac wrote:I've seen that exact scenario in practice.
With respect, that lethal scenario, and the grounding option I suggested, are very different indeed and completely unrelated.
It's not unusual to have a bad ground.
Obviously, a high ground impedance can occur, but the likelihood depends on where you live (ie. the local electrical safety regulations) and the type of mains supply configuration coming into the building. Its extremely unusual to have a 'bad ground' in the UK, for example. YMMV.
I don't know what's inside these "magical" ground plugs. I hope there's an RC circuit to prevent the worst.
There's nothing magical. It's a piece of wire. An RC circuit would defeat its object. It's not a ground-lift, it's a ground-tie, replicating the hard-ground connection provided in a class-1 device.
Unfortunately, it was the one receptacle that was connected directly to mains, next to the fuse box.
That wouldn't be legal in the UK, and I'm rather surprised it's allowed where you are. :o
It's purpose was to provide light for the electrician when the fuse box shut off.
Have they never heard of torches? :headbang:
Somehow, the thing that was powered by this one connection had bad insulation.
Oh dear... substandard routine maintenance? Any needless loss of life is tragic, and I'm very sorry for your loss. But this story involves multiple catastrophic failures combined with stupidity -- albeit none the fault of your late friend. It's an inherent fact of life that it's always impossible to protect against multiple simultaneous failures of critical parts of the system. That's why we try to engineer systems so that they fail-safe with a single failure.
You should never, ever, connect audio ground to mains ground. Period.
Sorry. That's complete nonsense. There are good scientific reasons why the audio reference ground ~should~ be tied to the mains safety ground in most mains powered systems, and thats been the practical implementation in every professional studio installation I've ever been involved with.
However, multiple connections between the audio reference hround and the mains safety earth can cause problems in some systems, obviously (ground loops), just as an absence of hard grounding can cause problems in others -- especially in systems with unbalanced connections. Having said all that, a connection to mains ground is not always an essential if the system is designed properly -- as in battery powered equipment, for example, or in vehicles, or planes...
People still die every year cause some bozo decides he's smart enough to wire the plug. I see those kinds of errors at least once a week when trouble shooting.
Sad but true... the only cure is education...