The 121 kA breaking capacity at 240 V AC tells you it can interrupt very high fault currents without the arc re-striking; at 415 V AC that figure drops to 75.6 kA, and at 690 V AC it's still rated at 11.9 kA. That's a lot of headroom for most industrial panels, so selectivity with downstream breakers is achievable even on large-transformer secondaries.
Auxiliary and undervoltage release configuration
This variant ships with two auxiliary switches plus one trip-alarm switch (HQ type) and an undervoltage release (UVR) factory-installed. The auxiliary contacts let a PLC or SCADA system read the breaker's open/closed and tripped states without extra interposing relays. All fit within the standard 76.2 mm width, so no extra DIN-rail space is consumed.
The 16 A rating holds from 40 °C up to 55 °C ambient, then derates to 15 A at 60 °C and stays there through 70 °C.