The ABB GDA203 AC‑63/0.03 is a Residual Current Device (RCD) from the ABB GDA200 series designed to provide earth‑fault (ground‑fault) protection in AC electrical circuits. It protects people and equipment from the effects of earth leakage currents by detecting an imbalance between live conductors and tripping the circuit when leakage exceeds the set threshold (30 mA). The device is intended for use in three‑phase systems and is often assembled together with circuit breakers in distribution boards to provide safety against electric shock and fire hazards.
