A transformer (100, 200) comprising: a first drive winding (112, 206) wound on a first core (102, 202), wherein the transformer (100, 200) is adapted to drive the first drive winding (112, 206) with a first high frequency square wave current; a second drive winding (114, 208) wound on a second core (104, 204), wherein the transformer (100, 200) is adapted to drive the second drive winding (114, 208) with a second high frequency square wave current, and wherein the second high frequency square wave current has an opposite polarity of the first high frequency square wave current; a sense winding (110, 210) wound across the first and second cores (102, 104, 202, 204); a compensation winding (108, 212) wound across the first and second cores (102, 104, 202, 204); and one or more utility lines that are threaded through a middle of the first and second cores (102, 104, 202, 204), wherein the utility lines are adapted such that a common mode current in the one or more utility lines causes one or more pulses to appear on the sense winding (110, 210), wherein the transformer (100, 200) is adapted to adjust a current on the compensation winding (108, 212) until the one or more pulses on the sense winding (110, 210) are cancelled out, and wherein the common mode current on the one or more utility lines is the adjusted current on the compensation winding (108, 212) multiplied by a turn ratio between the compensation winding (108, 212) and the sense winding (110, 210), characterized in that the first core (102, 202) has a lower saturation flux density than the second core (104, 204), and wherein the transformer (100, 200) is configured to drive the first drive winding (112, 206) with less current than the second drive winding (114, 208) such that the first core (102, 202) saturates at substantially the same time as the second core (104, 204). a first drive winding (112, 206) wound on a first core (102, 202), wherein the transformer (100, 200) is adapted to drive the first drive winding (112, 206) with a first high frequency square wave current; a second drive winding (114, 208) wound on a second core (104, 204), wherein the transformer (100, 200) is adapted to drive the second drive winding (114, 208) with a second high frequency square wave current, and wherein the second high frequency square wave current has an opposite polarity of the first high frequency square wave current; a sense winding (110, 210) wound across the first and second cores (102, 104, 202, 204); a compensation winding (108, 212) wound across the first and second cores (102, 104, 202, 204); and one or more utility lines that are threaded through a middle of the first and second cores (102, 104, 202, 204), wherein the utility lines are adapted such that a common mode current in the one or more utility lines causes one or more pulses to appear on the sense winding (110, 210), wherein the transformer (100, 200) is adapted to adjust a current on the compensation winding (108, 212) until the one or more pulses on the sense winding (110, 210) are cancelled out, and wherein the common mode current on the one or more utility lines is the adjusted current on the compensation winding (108, 212) multiplied by a turn ratio between the compensation winding (108, 212) and the sense winding (110, 210), characterized in that the first core (102, 202) has a lower saturation flux density than the second core (104, 204), and wherein the transformer (100, 200) is configured to drive the first drive winding (112, 206) with less current than the second drive winding (114, 208) such that the first core (102, 202) saturates at substantially the same time as the second core (104, 204).