For a fault at F2, i.e. outside the generator differential zone, the generator contribution flows
through both sets of CTs. If both sets of CTs reproduce the primary current accurately, there will
be no current in the operating winding.
For a fault at F1, i.e. within the differential zone of protection, the generator contribution
flows through one set of CTs and the system contribution flows through the other set of CTs.
Each restraint winding sees its associated current flowing in opposite directions (which decreases
the net restraining torque) and the operating winding sees the sum of the two contributions, i.e.
53.24 A.