There's a fair amount of bullshit in that thread - yanks, as an overly general rule, don't get electricity. A GFCI (ground fault circuit interruptor) is what we call an RCD, a residual current device. It monitors the active an neutral lines and if there's more current going out one way then there is coming back the other, must mean current's going to ground some where, and it cuts the power. That current can be leaving through you, or through the earth wire. Another protection circuit is an ELCB, an earth leakage circuit breaker. They detect any current flow through the earth pin, but won't trip if current goes out the active and through you - only useful if the ground is intact. If this bloke's earth was intact, without either of these two protections, it wouldn't have happened - it would have blown the fuse soon as the element blew because of a sudden short to ground, as opposed to waiting there for the brewer to touch it. I think it's odd for an element to fail and short itself to the sheath, I thought they were designed not to do that, but anyway. The most basic protection, and one you can't afford to screw up, is a good, solid, tight earth connection. Next is an ELCB, best is an RCD - newer homes will have these in the fuse box, if you've got the ceramic and tinfoil fuse jobs, you really should have an RCD on your brew outlet. Make sure everything is insulated properly, not like
this guy using a coffee cup FFS. Put strain relief on all cables, so that pulling on the wire doesn't pull on the connections. Don't strip insulation any further than it needs to, and make sure no connections have loose braids. Put emergency stop switches EVERYWHERE, which cut power to the entire brewery. Don't brew barefoot (this goes for you gasheads too), and I don't mean thongs.
Above all, don't mess with power if you don't understand it. If you screw it up, you can kill yourself or others. Same goes for gas - I was horrified at the thread today by the bloke who melted his nasa hose. Take an OH&S course if you need to, but whatever you do, make it safe first, productive second.