Hirschmann usually test their products according PLC standard EN 61131-2. The respective Installation Guide lists the standards.

With DC voltage a Power Failure Bridging Time of at least 10 ms is checked. The actual value could be a lot larger due to tolerances of the used electronic parts.

With AC voltage a Power Failure Bridging Time of one half wave is checked, which at 50 Hz also is 10 ms. Devices which can be operated with 50 Hz and 60 Hz offer the same time value at 60 Hz, because the energy buffer after rectification is the same.