The Siemens 3VA1020-3ED42-0AA0-ZD00 is a 4-pole IEC frame 100 circuit breaker from the 3VA1 series, rated at 20 A with a 25 kA breaking capacity at 415 V (class N). This is a line-protection device with a fixed thermal-magnetic trip unit (TM210, FTFM), meaning the overload protection Ir is fixed at 20 A and the short-circuit protection Ii is fixed at 16 times In (320 A).
For a 20 A line protection breaker on a 415 V three-phase supply, this gives substantial SCCR headroom in most distribution panels. The fixed thermal setting (Ir = In = 20 A) means no adjustment dial; the breaker trips at exactly its rated current on overload. The fixed magnetic pickup at 16 x In (320 A) is typical for line protection, clearing high-impedance faults fast without nuisance tripping on motor inrush.
This class of IEC molded-case circuit breaker is used in distribution boards, panelboards, and OEM machinery enclosures for branch-circuit protection on 415 V three-phase supplies. The nut keeper kit and DC Power OEM designation suggest it was specified for a Chinese OEM integrating into a DC power supply or UPS cabinet — the breaker itself is AC-rated, but the accessory kit and OEM variant code (ZD00) align with that supply chain.