RCD and RCCB
Residual current devices trip when current leaks to earth — protecting people from electric shock.
Easy
An RCD compares the current in the phase and neutral using a core-balance transformer. If they differ — current is flowing to earth, perhaps through a person — it trips.
- 30 mA — personal protection against shock (sockets, bathrooms).
- 100–300 mA — fire protection for whole installations.
Types: AC (sinusoidal leakage), A (also pulsating DC — required for many electronic loads), B (smooth DC, e.g. EV chargers and solar inverters). An RCBO combines RCD and MCB in one device. Press the test button regularly. An RCD does not protect against a phase-to-neutral shock (current through the body between phase and neutral is balanced).
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