I read somewhere that only the direction of the ac [in a fuse...or power
cord for that matter] towards the business end of the component[what is
heard] is of any value in directional break-in ,hence, the reason there
is directionality in a fuse used in an ac circuit is because of the
cycle going to... and not fro. For what its worth,it sounds plausible.
There can be reasons why a cable has directionality (mostly having to do with how the shield is constructed; this has nothing to do with fuses). But this bit: "the reason there
is directionality in a fuse used in an ac circuit is because of the
cycle going to... and not fro." - is a false statement (and is false because AC does indeed go "to and fro", if it does not, its called 'DC'). Therefore its not plausible that a fuse can be directional, and anyone telling you otherwise is trying to sell something and is hoping you are gullible enough to not see the fraud.
To understand the fraud that is happening here, you first have to understand that in an AC circuit, the voltage drop across the component has to be the same in both directions. Otherwise one of two things will happen, both governed by Ohm's Law: either the component will heat up (as in the case of an electrolytic capacitor when reverse biased by half of the AC current flow; this will cause it to heat up and explode) or rectification will occur (as in the case of a power rectifier, which can conduct in one direction but not the other- this BTW is how AC is converted to DC). So if a fuse is directional (entertaining that impossibility for a moment) that means that it will have a resistance value of x in one direction (some fraction of an Ohm) and in the other direction the resistance will be x plus something more. The idea is of course ridiculous, as if this were the case, the additional voltage drop in the higher impedance direction would cause the fuse to heat up with eventual failure. This is Ohm's Law we're dealing with here- its a simple formula and can't be violated without creating a new branch of physics. So if anyone tells you that fuse direction make a difference, either they are grossly misinformed or just outright lying.
It really is that simple.