Are you referring to AS/NZS 3000? I’ve never come across that here in the states, that’s some interesting reading and makes perfect sense.

On the practical side without engineering calculations, daisychaining extension cords will simply exacerbate voltage drop, which coupled with increased line resistance, will just cause increased current draw and increased thermal dissipation on the cord (those cords everyone’s dad has where the outer jacket is shrunk to hell against the internal wires), and poor reactance of (especially motor driven) equipment. This can be alleviated by using thicker cords (eg #10), but it still has limitations over excessive distance. A small battery charger will probably continue to work, whereas a table saw will have problems.

On the safety side, even sticking your finger on the load terminal of a 20a breaker will not trip it, even barefoot, as the human body doesn’t draw enough current, it just zaps the hell out of you. OCPDs are typically designed for system and equipment protection. GFCIs are more effective at protecting a person, but only if the current deviates to a different ground path. As far as I can tell from preliminary reading, the purpose of calculating loop impedance is determining the effectiveness of the grounding (earthing) conductor in relation to distance from the actual transformer. In a real world scenario, this is more going to be say if a cord were to be cut or equipment faults to ground, and whether the impedance exceeds the physical limitations of the wire to trip the breaker (or fuse).

The short answer is rating changed. We got more and more devices that required higher amperage ratings. So we went from 110 (which was what most homes were rated for in the 50’s) to 120. But if you happened to have an old extension cord lying around in your basement from before the change etc you absolutely could overload it.

The real problem though is that some devices you might use an extension cord for (lets say a welder because I know from experience those require more power than a standard 20’ extension cord puts out), require a certain gauge of wire to carry that power. If that wire is too small or the power source is insufficient, it’s likely no electricity will flow (without flaws in the circuit).

There are various kinds of extension cords made for various uses. Longer = more money, fused = more money, larger wire = more money. More insulation/weather proof plugs = more money.

You probably don’t need a big beefy extension cord for the lamp in the hallway. But you might need it for your weedwacker.

But if, say you hooked up an outlet dedicated for something like a washer/dryer. And you used the correct extension cord to connect to that outlet. Now let’s say you attach an older extension cord or power strip to that extension cord. One that doesn’t have an internal breaker to trip (there’s definitely a fair number that didn’t, back in the day). It would be an astronomically bad idea to attach your welder (or any high draw device) to that circuit. You absolutely can and will let the smoke out of your wires and where there is smoke there is fire.

Yes but I was emphasizing the parallels to the USB c problem.

In USBC if you use a 200 watt cable that has 200 watts going through it and then extend it with a 15 watt USB c cable, the 15 watt cable will over heat.

If you plug a 30 amp load into a 30 amp cable and then extend it with a 15 amp extension cord, you will get overheating on the 15 amp extension.