What it is and what the ratings mean
The Siemens 5SM1317-6FD is an FI-Protector Type A residual current device (RCD) with overcurrent protection, built for panel-mounting on a DIN rail. It's rated 80A, 2-pole, with a 30mA trip sensitivity at 230V. The 55mm width (2.5TE) means it takes up two and a half 18mm module spaces on the rail — a factor when you're packing breakers into a crowded enclosure. Type A detection means it catches both sinusoidal AC fault currents and pulsating DC fault currents, which is the standard requirement for circuits supplying single-phase electronics, variable-speed drives, or washing machines. The 30mA IΔn is the standard for personal protection against electric shock in residential and commercial final circuits.