Cold Load Protection
51 elements are affected by the setting of the 51CL Cold Load function.
51CL can be configured for any 51 Time-Delayed Overcurrent element to automatically apply modified
settings following a CB close after an extended open state to pick up Cold Load at an elevated level which
could exceed the normal protection tripping level and then revert to normal settings after a configurable
period of time or if the load current reduces to below a set level.
The setting of each shaped overcurrent element (51-n) can be inhibited and alternative Cold Load settings
can be applied for a period following circuit switch in.
During Cold Load settings conditions any directional settings applied in the phase overcurrent menu are still
applicable.
A CB Don’t Believe It (DBI) condition is not acted on, causing the element to remain operating in accord-
ance with the relevant 51-n settings. Where the Reduced Current setting is disabled, reversion to 51-n
settings will only occur at the end of the Drop-off time. If any element is picked up on expiry of Drop-off
time, the relay will issue a trip and lockout.
If the circuit-breaker is re-opened before expiry of the Drop-off time, the drop-off timer is held but not reset.
Resetting the timer for each trip could result in damaging levels of current flowing for a prolonged period
during a rapid sequence of trips/closes.
Cold load trips use the same binary output(s) as the associated 51-n element.
Protection and Automation Functions
5.17 51 Time-Delayed Overcurrent – Phase
Reyrolle 7SR5, Overcurrent Protection Device, Device Manual 251
C53000-G7040-C014-1, Edition 11.2019
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