Cookie RCDs have a transformer built in the RCD which detect voltage leaking. Does that explain it better
They do incorporate a transformer, but that's not how an RCD works.
Voltage doesn't leak, it can't, voltage is a measure of the energy difference between two points.
Current flows, and can 'leak', but an RCD does not detect leakage (not directly).
An RCD (single phase version) has two transformer coils wound around a common core, one is for the live and the other for the neutral. There is a third coil around the same core which operates the tripping mechanism.
If the current flowing through the live coil is equal to the current flowing through the neutral then they are balanced and the cancel out and no current is induced in the tripping coil.
If a more current flows through one coil than the other then they are not balanced and a current is induced in the tripping coil and the RCD trips.
So an RCD detects an imbalance of current between live and neutral.
It doesn't matter why there is an imbalance, it could be leakage, someone receiving and electric shock, a caoacitir charging, incorrect wiring, short circuit etc etc.
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I know how they work, they use a differential coil to sum zero sequence currents. The thing is I don't exactly get how eletrmechanical RCDs respond faster to high current ground fault vs low current ground faults.
I don't know how many RCDs are purely electromechanical these days, I think a lot of them incorporate some electronics.
This probably has something to do with the faster reaction to higher fault currents.