Eaton EDR 3000 Installation, Operation And Maintenance Manual page 557

Locking
A locking signal will be issued simultaneously with the BF -Signal (Trip). The locking signal is permanent. This signal has
to be acknowledged at the HMI.
Note on devices that offer Wide Frequency Range measurement:
The supervision scheme 50BF will be blocked as soon as the frequency
differs more than 5% from the nominal frequency. As long as the frequency
differs more than 5% from the nominal frequency the supervision scheme
"50BF and CB Pos" will work according to the "CB Pos" scheme.
EDR-3000
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