The Siemens 3VU9135-1AB02 is an accessory designed for the 3VS13 three-phase bus bars used in 2MSP applications. It mounts directly onto the bus bar assembly, providing the necessary interface for connecting downstream protection or switching devices in a panel.
This part carries an NRND (Not Recommended for New Designs) status. That means Siemens has flagged it for eventual phase-out — it is not yet discontinued, but it is no longer the preferred choice for new panel builds or BOM lines. If you are freezing a new BOM, check whether the 3VS13 bus bar family has a current-production accessory alternative.