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do you have such protection (differential switch) on the wiring of buildings ?In USA and Canada it is called "Ground Fault Circuit Interrupter", GFI or GFCI.
In the UK electrical systems the name is "Residual Current Device", something like that.
Wikipedia English article on RCD/GFI is UK point of view with comments about US and other areas.
I like your name "Interruttore differenziale" better. The GFI does not need a ground to operate, and can trip even when current is leaking to someplace other than ground. These all operate on a *difference* in current in the two legs of the circuit.
In the USA, GFIs were required on bathroom outlets in the 1970s, then in many more places, but not in the whole house. Older units are outlets, which may power (and protect) additional outlets. Now it is common (in new-work) to put the GFI in the cellar fuse-box, built with the over-current protection in standard circuit-breaker format. This is also available on the UK market. Yours (in the Wikipedia pictures) appear to be 2-in-1 units with an over-current breaker permanently strapped to a GFI breaker, a bit more bulky. (I suspect that you can now get them all-in-one, narrower.)
One global difference. In the US market the trip current (after many milliSeconds) is 5mA. The UK market GFIs are marked 30mA (your pictures show 0.030A which is 30mA). While this sounds like a big difference, I once went through the details and decided it was not a BIG difference in protection, but a difference in the way they are tested and marked.
There are, in addition, in both markets, "equipment protection" GFIs with much higher leakage trip currents. A motor in a damp location may leak 10mA "normally", so a 6mA GFI would keep tripping. The "differential" is never perfect, so a 100 Amp starting-surge with 0.9999000 accuracy will trip a 6mA GFI. You can get 50ma and 100mA GFIs if you are only protecting equipment, not people.
I am shocked to learn that Germany did not require RCD until 2007?
In the UK, apparently you can have one RCD for the entire house. Better is to separate power and lights, and have at least two RCDs for the lighting circuits so the whole house won't go dark. This is never done in the US. We put GFI only where "needed". This can be a non-GFI circuit to bedroom and bathroom with a GFI outlet for the bathroom. Because of our smaller circuits (120V 20A vs 230V 16A) and large hair-dryers, we now favor a dedicated bathroom circuit with GFI preferably in fuse-box. I have 25 circuits in my house, four breakers (bathrooms and kitchen) are GFI, and one non-GFI breaker feeds GFI outlets on the outside of the house.
We put GFI in kitchens and bathrooms because water pipes were all metal, good way to get shocked. However as I was installing all those GFIs, I was also converting all plumbing (water and drain) to plastic pipe. So it is a bit silly.
Your next step, which you should resist, is "Arc Fault". The idea is that when there is a bad connection in a plug and outlet, and it heats-up, the AFCI should detect this and break power before a fire stars. These do not work!!, except in very severe cases, maybe. They trip for no reason, they give false hope of safety, and they cost way too much. 
Topic: Neutral Switching (Read 4097 times)