Overload relay and method for operating such an overload relay

摘要

The method involves measuring power of a phase for a channel. A maximum power and an asymmetric value are determined as maximum of three powers and maximum of paired differences of the powers, respectively. An operating mode is retrieved for indicating whether an asymmetrical detection is performed. The asymmetric value is set as zero, when no detection is performed. A model value for heating a three-phase load (4) is calculated with respect to its proximity based on maximum power value and the asymmetric value. The load is switched off, when the model value exceeds a predetermined threshold. An independent claim is also included for a three-channel overload relay.