What does it mean when one refers to, Positive Negative Zero sequence voltages/currents in relation to 3 phase power system? My blunt understanding is that in say positive sequence voltages, as we rotate around the phasor diagram in a clockwise manner we see the voltages in the following sequence: A, B, C, A, B, C... And so on. In negative sequence voltages the sequence is reversed like so, C, B, A, C, B, A... And so on. Am I understanding this correctly? Why do we chose to make such a distinction anyways? Also, what does one mean when they refer to zero sequence quantities? Thanks again!