Issue:
Definition of CLPU

Environment:
Easergy P3 Protection function

Resolution
Cold load pickup is an overcurrent condition that takes place when a distribution circuit is re-energized following an extended outage. It is referred to as cold load because the power supply has been unavailable for a period so that the load has reached a “cold” state before being re-energized.  In most cases the cold load pickup current is greater than the pre-outage current. This will cause protection relay tripping as the cold load current will be misinterpreted as if it is a fault current  (meanwhile the circuit is healthy).

The increase in the cold load pickup current is due to inrush currents and loss of load diversity since all loads are switched on and drawing current at the same time after re-energization. Cold load pick up current consists of a combination of more than one type of load currents that should be taken into consideration (example: continuously operating load current, transformer magnetizing current, capacitor inrush current, etc.)

Released for: Schneider Electric United Arab Emirates