Its 15 kA rated ultimate breaking capacity (Icu) at 230/400 V AC means it can safely interrupt a fault current up to that level on a 400 V three-phase supply or a 230 V single-phase line without welding its contacts or cascading the fault upstream — critical for panel selectivity when coordinating with upstream MCCBs or fuses.
What the D-curve and breaking capacity mean on the panel
The D-curve (10–20× In magnetic trip) is sized for loads with high inrush — think motor starters, small transformers, or solenoid banks on a packaging line.