There is a reason for USB-C extensions not to be part of the standard. They can be bothersome in the best case and dangerous in the worst.
There is a reason for USB-C extensions not to be part of the standard. They can be bothersome in the best case and dangerous in the worst.
Going to take a wild guess and say the same reason you shouldn’t chain extension cords. USB can carry over 200w these days.
what if I don’t know that either
It all depends on current draw vs wire size over distance.
No, that’s not the reason at all. The actual reason is a phenomenon called “loop impedance”, which increases exponentially with each additional plug connection you chain together, regardless of the wire guage and distance of the extension
Too high loop impedance can cause your RCD to no longer trigger if you accidentally touch an exposed live connection, which is a major electrocution risk
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).
Yeah, I think in this case there’s a lot more tiny conductors sharing what can add up to pretty high current loads on PD connections. Adding extra connectors adding resistance to low (5-20v) voltage high current connections is adding an extra failure point and increasing resistance on the whole cable run.
Not inherently unsafe, but just not a good idea to promote because you know someone will try to run a 200w charging cable for 30m with like 5 connected cables.
I would hope that a device capable of pulling 200w from USB would be intelligent enough to detect the excessive voltage drop and error out or reduce the current.