
Fault Current Analysis 229
(unbalanced) three-phase voltages into three sets of symmetrical (balanced) volt-
ages, one with phase difference of +120° (positive sequence), one with phase
difference of –120° (negative sequence), and one with no phase difference at all
(zero sequence). The resulting three symmetrical component currents are then
determined using the following,
symmetrical component current
symmetrical componen
=
tt voltage
symmetrical component impedance
(9.24)
Unsymmetrical phase currents = Phasor sum of three symmetrical
component currents (9.25)
We give below the nal results for the fault currents in the most frequen ...