From the amplitude-matched resultant currents I̲am,N,a and I̲am,Y,a, the differential and restraining currents are calculated as follows:

Id,N,a = |I̲am,N,a + I̲am,Y,a|

IR,N,a = |I̲am,N,a|

Again, the equation for the differential current applies under the condition of uniformly defined current arrows relative to the protected object. Both current arrows point either towards the protected object or away from it.

Fig. 3-106 shows the tripping characteristic of the ground differential protection function. The characteristic equation is as follows:

with

Idiff>,N,a: setting at REF_1: Idiff> PSx