Residual current device for panel protection
The Siemens 5SM1317-0FD is a Type AC residual current device (RCD) rated 80 A with a 30 mA trip sensitivity, 2-pole, 230 V, in a 55 mm wide housing occupying 2.5 TE on a DIN rail. Type AC means it detects sinusoidal AC earth faults only — no pulsed DC or smooth DC component. That matters: if your downstream loads include VFDs, switched-mode supplies, or single-phase rectifiers, Type AC may nuisance-trip on the DC component; you'd want Type A or B instead. For purely resistive or inductive AC loads without rectification, this is the standard choice.
What the ratings mean for fit
80 A rated current matches the upstream breaker or load-break switch in a sub-distribution board; 30 mA sensitivity is the standard for personal protection against direct contact (IEC 60364-4-41). The 2-pole form factor interrupts both line and neutral on a single-phase circuit. At 2.5 TE (about 55 mm), it takes up two-and-a-half 18 mm module spaces on a DIN rail — plan your enclosure fill factor accordingly.