The DIFF-Monitor enables the tripping characteristic and operating times of differential protection relays to be checked.
Test values are calculated automatically with reference to the nominal data of the transformer and the HV/LV data. With transformers using phase-rotation vector groups, for example YD 5, the programme performs a phase adjustment between the currents of the high-voltage and low-voltage side which are to be compared. In addition to the vector group adjustment, an amplitude adjustment is also performed.
Tests are evaluated with reference to the stabilization characteristic of the differential protection device.