GFCIs are great: they detect even small leakage currents and modern ones also detect neutral-to-ground faults. But, in the US, it’s very unusual to have any sor

GFCIs are great: they detect even small leakage currents and modern ones also detect neutral-to-ground faults. But, in the US, it’s very unusual to have any sort of ground fault/residual current protection on anything other than individual branch circuits, and even then it’s usually just the outlets. GFCIs are also fixed at 5mA, and they don’t coordinate with each other (meaning that if you have two GFCIs in series, they are both likely to trip in the event of a fault). So individual outdoor wires in rust metallic conduit without GFCI protection are very common. Outdoor receptacles in nice “extra-duty” boxes, where the receptacle itself has “weather resistant” GFCI (modern code) are very common, and nothing protects effectively against water getting into the box itself and causing a problem immediately upstream of that fancy GFCI. I don’t understand the European codes well, but as I understand it, it’s common to have a big RCD in the distribution box, and that will protect the distributed wiring even if it doesn’t have the magical 5mA threshold that supposedly makes wires extra safe if you touch them by accident. (I’d like to see standardized ratios of ground fault current sensitivity to breaker size, so a 15A residual current device downstream of a 60A one would coordinate properly. The hardware is cheap enough these days that this could be done cost-effectively.