Images for the question asked by Dan. First, in answering his question based on a more thorough mathematical and direct approach, I would need to begin with a few assumptions:
ONE: that these figures and calculations are going to be based on unity power factor and a balanced 3-Phase load.
TWO: that “a” and “b” [lowercase] are referencing the secondary labels and that B A C [uppercase] are also referring to secondary labels. [I say this because generally lowercase a,b,c refers to secondary labels and uppercase A,B,C refer to primary labels.]
THREE: that the ‘b’ and ‘a’ CTs were swapped or mis-wired and that the voltages to the meter potential coils have remained in their correct positions.