It uses an ETU350 electronic trip unit — adjustable long-time (Ir 0.5–1 000 A), short-time (tsd 0.04–0.4 s), and instantaneous (Ii up to 10 000 A). The interrupting ratings are 242 kA at 240 V, 187 kA at 415 V, and 74 kA at 690 V, so it handles high-fault-capacity mains feeders or large sub-distribution.
Thermal derating — the real usable current
The breaker holds its full 1 000 A rating up to 55 °C ambient. At 60 °C it derates to 955 A, at 65 °C to 885 A, and at 70 °C to 815 A. That means in a hot panel — say a packed switchboard near a furnace line — you lose nearly 20 % of the rated current.