The Siemens 3VU9135-1BB03-0RE0 is an accessory for the 3VU13 switch, specifically a 3-phase infeed terminal connection from below for a busbar system.
Deployment context
Mounts to the 3VU13 switch's busbar system, routing the three-phase supply from below — a common panel layout for motor feeder or distribution blocks where top-entry space is constrained.