Transformer-protection circuit breaker, size S00
The Siemens 3RV2811-1DD10 is a SIRIUS circuit breaker designed specifically for transformer protection, complying with UL 489 and CSA C22.2 No.5. That means it's listed for the inrush and overload profile of a transformer primary — not a general motor-protective breaker, but a dedicated device for that duty. Rated breaking capacity hits 100 kA at 400 V AC and 500 V AC, dropping to 10 kA at 690 V AC. The S00 frame (45 mm wide, 97 mm deep, 144 mm tall) fits standard panel layouts; the 45 mm width is one standard module, so it occupies a single slot in a typical distribution board.
Fuse backup coordination
The breaker specifies required upstream fuse ratings: gG 32 A at 400 V and 500 V, gG 25 A at 690 V. This is the coordination data a site electrical engineer needs for selectivity studies — without the right gG fuse ahead, the breaker's 100 kA rating isn't valid at those voltages.
Main contact screws are M4; use a Pozidriv size 2 tip with a 5–6 mm shaft diameter. No ground-fault or phase-failure detection built in — this is a straight thermal-magnetic breaker, not a multifunction motor-protective device.