I have very little worry that my carpet can accidentally negotiate 60w and up.
I _am_ worried about cheap USB-PD devices that forgoe this negotiation as it is complex and expensive to implement.
Yes. Moving critical safety limits into software? https://en.wikipedia.org/wiki/Therac-25 Let's hope they're all up to the challenge ...
If you buy a fake cable that pretends to have display-port alternate mode or something but doesn't, meh, you're out 10 bucks. But if it pretends to be able to carry 200 W but isn't and burns your house down instead, you might be out a tad bit more...
USB-PD has bidirectional communication, so at least in theory both ends could know how the cable is performing by comparing voltage and current measurements at either end.
If the cable drops too many Watts, the load can be disconnected.
As I've commented elsewhere, I wonder if, at that point, there still is that much of a point in sticking with USB-C for what seem like fairly specific applications.
I mean, if we're at the point of carting around such a monster of a laptop, will an additional, dedicated, power-only connector make that much of a difference? Don't get me wrong, I'm actually somewhat tempted by such a thing, but just because it would be easy no move around, not for actually carrying on my back all day every day.
There are some mitigations though, like the cables must identify what they can handle (else the high current modes can't be used), and both ends needs to verify the plug and cable etc.
In theory though I don't see why they couldn't include this in the standard.
What I don't understand is how the cable doesn't have a way to detect a short circuit. I'd imagine that a 250 watts capable cable would have more safety features hopefully though.
It's a good question. Generally speaking, DC is considered a shock hazard at or above 60V, but OSHA recognizes 50-60V as being potentially hazardous. It's certainly an arc hazard when disconnecting as the article notes. And 5A at just about any voltage will start a fire in case of a short circuit.
Myself and most people I know always considered USB connection to be safe-ish - that is, you can keep the cable connected on the supply side, and have the receiver end just lie on the desk on the floor, and the worst that could possibly happen is some tiny sparking if the stray end touches something conductive in a very unlucky way. But the more power I see pushed through these cables, the more I start to look at them as live wires hooked to mains power.
Additionally, such wattage sounds like a serious fire hazard if the cable is damaged, which means the cables themselves need to be handled with care. Something that wasn't the case with typical USB charging until recently.