DIFFERENTIAL PROTECTION METHOD AND DIFFERENTIAL PROTECTION DEVICE FOR PERFORMING A DIFFERENTIAL PROTECTION METHOD

摘要

The invention relates to a differential protection method for generating an error signal in which current measured values are respectively measured at at least two different measuring points (M1 M2) of a multiphase transformer (10) for each phase (A B C) the current measured values for each phase (A B C) are used to form differential current values and stabilization values and the error signal is generated if it is determined during a trigger range test that a measured value pair of at least one of the phases (A B C) which is formed using one of the differential current values and the associated stabilization value in each case is in a predefined trigger range (23). In order to be able to selectively and reliably distinguish an external error from an internal error if the transformer (10) has an earthed neutral point (14) it is proposed that a zero phase sequence system current flowing through the neutral point (14) is used to form the stabilization values. The invention also relates to a corresponding differential protection device (11) for performing such a differential protection method.