For the external fault at F2, 23.28 A flow through both CT secondary circuits and nothing flows
in the overcurrent relay.
For the internal fault at F1, 23.28 A flow through only one CT secondary and the operating coil
of 87.
∗ Although 51 is the ANSI recommended device function number for an overcurrent relay, this relay is connected as a differential
relay and the designation 87 is more meaningful for this application.