Why it is not important where we connect our hot and neutral wire when connecting them to our Schuko plug? Is it because current flows in both directions?
It is only important that our ground wire is connected in the middle but I don't understand why the order of our hot and neutral wire is not important while connecting them to Schuko.
Answer
Schuko is a standard used primarily in Germany and Austria. (PS: Also in the Netherlands.) Neighbouring countries have different standards which are compatible to some extent (protective earth gets in the way) and mostly asymmetric. The plug in sweber's image is the most common type in Europe because it fits into most of them and so covers most of the European market. (I am assuming plugs that have protective earth. Among those without, euro plugs are even more common because they are even more compatible, e.g. with the Italian and Swiss systems. Due to a euro plug's flexibility, it even works with different pin distances.)
The standard dates back to a time when very often both wires were live at the same time. An electrician in Berlin told me that he once still worked in a place with extremely old wiring where this was still the case. Before changing something, he checked one wire, which was live, and so assumed that the other would be neutral. It was live, too. Before that background, the symmetry makes sense, though it does indicate a certain lack of foresight.
While obviously not ideal, this symmetry is not a big problem so long as all appliances are built in such a way as to be still safe when the two main wires are swapped. As almost everything is being produced for a global market today, in practice this is always the case - or at least manufacturers always claim and usually provide it. It will be like that until the countries without the symmetry provide the overwhelming majority of consumers, at which point the few remaining ones will have to switch as well.
The responsible standards bodies and authorities in Germany and Austria are so little concerned about this that when you buy a switchable power strip here, the switch almost(?) always cuts off only one of the wires, which of course in a symmetric system may be the neutral one. Though this should theoretically be a factor in accidents occasionally, I have never heard of one and nobody seems to be worried about this. Nowadays the old schuko plugs without the French hole are so rare that it would be no problem to introduce new schuko sockets that simply add the French pin to the existing schuko standard, resulting in three connections for protective earth and solving the problem at once. Or, even simpler, to just switch to French sockets. Apparently something similar already happened in Poland, where the old Russian system (like schuko but without the two protective earth connections that gave it its name; consequently, schuko plugs fit into Russian sockets but not vice versa) was replaced by the French system, though reportedly people are careless about the wiring, sometimes switching live and neutral.
The schuko system is rather strongly incompatible with the British one even now that the voltages have been unified all over Europe. The British system is traditionally asymmetric. During the Second(?) World War, as part of a war effort to save metal, people started to use thinner wiring than would otherwise have been necessary, but closed the wiring to a circle. So you have a neutral loop and a live loop, and you can add sockets or light switches to that at various points. This is actually quite dangerous because if the live or neutral circle gets disconnected once, you have no way to know that the wires are now loaded beyond their specification. I believe modern British standards still take this problem into account, and that this is why all British plugs must be individually fused, which could actually be dangerous if you put the fuse on the neutral wire. (In other words, schuko plugs must not be fused.)
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