Differential current protection device for electrical energy supply

摘要

A current differential protection arrangement for an electric energy supply unit has a measurement value pre-processing device and an evaluating device that checks whether the calculated differential and stabilisation current values lie in a locking or in a triggering range based on a predetermined relation between the differential current and a stabilisation current (characteristic reaction curve). An additional stabilisation range is provided in the locking range. In order to prevent such a protection device from causing a time-locked blocking state following an outer defect and causing saturation of the converter, the evaluating device (21) has a checking device (30) in a stabilising circuit (25) that checks whether the calculated current values define a point in the additional stabilisation range (31). If that is the case, a locking signal is generated to activate a locking device (37) arranged downstream of the checking device (30). When the detected current values subsequently define for the first time a point located outside of the additional stabilisation range (31), a time function element (40) is switched whose output is connected to a resetting input of the blocking device (38).