What this accessory does on a 3VU13 or 3VU16 switch
The Siemens 3VU9131-7AA00-0RE0 is a short-circuit signaling contact accessory for the 3VU13 and 3VU16 switch range. It adds a 1NO+1NC contact block that latches when the switch trips on a short-circuit fault, giving the control system a positive signal that the fault was a short rather than an overload — no guessing, no separate monitoring relay. The contact block fits within a 0.5 MW width on the DIN rail, so it does not eat extra panel space beyond the switch itself.