Oh, and breaker panel fusing usually 15-30A in 220V countries, typical IEC cable rating 6-10A. So the breaker will open when the cable from the wall is overstretched will it?
The main purpose of a breaker or fuse is to prevent fire.
So how hot will your typical IEC cable rating 6-10A get with a breaker panel fusing usually 15-30A.
Heat of cable = time + power.
What is the temperature rating of the insulation?
To have possibility to start a fire you have up to when insulation fails.
And NO the fuse or breaker is not there to protect the source of power in a properly designed power system. The power source has a fuse or breaker that serves this function.
Simple electricity rules apply.
From what you've said I suspect that you don't understand that we've been talking about the breaking capacity of a fuse, not its load capacity. The
load capacity of the fuse is the current it opens at (very approximately - the fuse's rating is more properly specified as some value of I
2t). The
breaking capacity is the flowing fault current that it can effectively interrupt or, put differently, the largest fault current that it guarantees to interrupt. That's why I say you have to consider the supply
in choosing the breaking capacity of the fuse.
The earlier example was of a 1A load capacity fuse with a 1.6kA breaking capacity versus a 1A fuse with a 35A breaking capacity. If the current flowing in a fault exceeds the breaking capacity of a fuse, that fuse will fail to open the circuit and can even induce a higher current fault itself, tripping the next bit of protection upstream. So, an example for the latter case would be that 1A glass fuse with a breaking capacity of only 35A. It's very easy to generate a fault current of >35A with a simple accidental dead short - loose wire, loose screw, that kind of thing. The 1A HRC fuse would break that fault current, the 1A glass fuse wouldn't and might even become a lower impedance than the fault it was trying to isolate.
A fuse that fails to isolate a fault in a point downstream of itself becomes a liability to points upstream of it and part of ensuring that does not happen is to choose a correct breaking capacity based on the upstream's potential for supplying a fault current to a downstream fault. Yes, part of the criteria for a fuse is "Does this have the breaking capacity to protect the upstream supply?". So in a "properly designed power system" properly chosen fuses/breakers protect
both the load and the supply.