3UF5 SIMOCODE-DP System Motor Protection and Control Device

The 3UF50 Basic Unit2.5.3 Earth Fault DetectionDescription of functionInternalfunctionNoteThe internal Earth Fault Detection function is only suitable for motors with a3-conductor connection and for earthed power systems! You can activatethe internal Earth Fault Detection function by means of parameterization. Itcovers two sets of circumstances during operation:• normal operation at up to 2 x I s . The operating current has to be less than doublethe Set Current I s . Fault currents amounting to > 30 % of the Set CurrentI s are detected.• starting or overload at above 2 x I s . The operating current is greater than doublethe Set Current I s . Fault currents amounting to > 15 % of the motor currentare detected.If you are using internal Earth Fault Detection with a Star Delta Starter connection,spurious tripping may occur. In delta operation the net current is notequal to zero because of harmonic waves.ExternalfunctionYou can operate internal Earth Fault Detection in parallel with ThermistorMotor Protection.With the 3UL22 summation current transformer, rated fault currents of 0.3A, 0.5 A and 1 A are evaluated. Response delay time: > 200 ms.If the earth-fault limit is exceeded, a signal is emitted. You can specify additionaltripping circumstances by means of parameterization.NoteThe external Earth Fault Detection function is an alternative to ThermistorMotor Protection (version of unit).If the rated fault currents are exceeded,SIMOCODE-DP responds either• with shutdown of the Contactor Controls QE1 / QE2 / QE3 or• with a warningdepending on what you have set.GWA 4NEB 631 4286-02a 2-17