Note that if you could design a faster breaker, more lives might actually be lost...
Imagine you had an ideal switch that could disconnect a circuit instantly.
Any devices powered on that circuit with transformers, inductors or motors in (think vacuum cleaners, power tools, microwaves, blenders, etc) will have a current flowing through them, and as that current is interrupted there will be a huge voltage spike - easily 10x the normal voltage for a few milliseconds.
If a human is touching that circuit, the 10x higher voltage will cause 10x more current to flow into the human.
Hooray - your 'safer' RCD kills more people.
The real solution is to have a more complex switch which disconnects the circuit at the same time as shorting out the circuit, to allow any current that was flowing to gradually dissipate into the wiring resistance. To my knowledge, such things don't exist today.
Isn't the solution a GFCI outlet at the wall, not at the breaker? Suppose you're in a bathroom; near water with a hair dryer, space heater, or some other non-inductive load. If there is a short, the circuit is cut from that outlet; inductive loads in the rest of the house aren't involved.
Well there can still be an inductive load that you're disconnecting... Like the vacuum cleaner you idiotically used to try and clean a wet carpet...
Luckily, the problem I described is almost a non-issue. Deaths due to electrocution in buildings with a GFCI have fallen to pretty much zero - there were only four deaths due to electrocution at home in the UK last year (where voltage is very high and RCD's are common). That figure includes deaths by suicide, lightning indoors, and deaths where an RCD wouldn't help such as poking around inside CRT's, so it's entirely possible an RCD is already saving every life.
Imagine you had an ideal switch that could disconnect a circuit instantly.
Any devices powered on that circuit with transformers, inductors or motors in (think vacuum cleaners, power tools, microwaves, blenders, etc) will have a current flowing through them, and as that current is interrupted there will be a huge voltage spike - easily 10x the normal voltage for a few milliseconds.
If a human is touching that circuit, the 10x higher voltage will cause 10x more current to flow into the human.
Hooray - your 'safer' RCD kills more people.
The real solution is to have a more complex switch which disconnects the circuit at the same time as shorting out the circuit, to allow any current that was flowing to gradually dissipate into the wiring resistance. To my knowledge, such things don't exist today.