What this breaker is and where it goes
The 3RV2411-1JA20 is a SIRIUS-branded circuit breaker from Siemens, designed specifically for transformer protection. Trip Class 10 means it clears a fault in under 10 seconds at 7.2× the thermal setting, which is the standard match for transformer inrush — you don't get nuisance trips on magnetizing current, but it still opens fast on a hard fault. The 100 kA breaking capacity at 240 V and 100 kA at 400 V give you headroom for high-fault panels without cascading upstream breakers.
Spring-loaded terminals on the main current circuit accept 2× (0.5 to 4 mm²) solid or stranded wire. Clearance distances: 50 mm upwards and downwards, 30 mm to the side, 0 mm forwards and backwards — so you can butt it against the backplane or a neighboring device without derating. Ground fault detection is not included, so if you need GF protection, plan an external relay.