The Schneider Electric A9N18567 is an Acti9 Vigi C120 add-on residual current device (RCD) — a voltage-independent, Type AC earth-leakage protection module rated for 125 A continuous current at 230...415 VAC, 50/60 Hz. It clips onto a 35 mm symmetrical DIN rail alongside a compatible MCB, adding 300 mA instantaneous ground-fault protection to the outgoing circuit. The 3-pole (3P) configuration covers three-phase loads; the 500 V rated insulation voltage (Ui) and 6 kV impulse withstand (Uimp) per IEC 60947-2 confirm it handles distribution-level transients without flashover.
Mounts via clip-on to a 35 mm symmetrical DIN rail — standard panel integration, no tools needed for the rail seat. The tunnel-type terminals accept 1...35 mm² flexible or 1...50 mm² rigid conductors; tighten to 3.5 N·m with a 15 mm strip length. The electrical connection to the upstream MCB is by screws, so verify the mating breaker's terminal layout before panel assembly.
The Acti9 family is Schneider's mainstream DIN-rail protection range, so replacement modules and matching MCBs remain widely available through standard distribution.
The 300 mA sensitivity is an instantaneous trip (no intentional time delay), so it clears earth faults without the nuisance coordination issues that delayed types can introduce on sensitive loads. Type AC detection covers sinusoidal AC residual currents — the common waveform from standard power supplies, heating elements, and motor drives without rectifier stages. If the downstream loads include variable-speed drives or switched-mode supplies that generate pulsed DC fault currents, a Type A or Type B RCD would be required; this Type AC unit is not rated for those waveforms. Mechanical durability is rated at 20,000 cycles — adequate for a distribution outgoer or group incomer where switching cycles are infrequent.