When applying current transformer supervision (CTS), the ground differential protection function may be blocked for the relevant end where a CT fault is detected. See details given in Chapter “Current Transformer Supervision (Function Group CTS)”.

When a CTS alarm signal is issued for one of the transformer ends (for example CTS: Alarm end a), the associated ground differential protection function is then blocked, if it has been set accordingly (for example by assigning REF_1 to end a: REF_1: CTS effective PSx = Yes).