Current phase-shift effects in the calculation of magnetic fields generated by double-circuit overhead transmission lines

Phase shifts between the two current phasor terns of double-circuit ac overhead transmission lines are observed in particular cases. This paper analyzes the effects of such phase shifts on the magnetic field generated by these lines. The load flows recorded for an existing double-circuit line are used to derive currents and phase shifts between current terns, and then to perform simple magnetic field calculations that show how current phase-shift can either enhance or reduce the field with respect to the zero phase-shift case, depending on the vertical arrangement of phase conductors. Neglecting such effects can lead to underestimate the field in some cases, to overestimate it in others (with errors up to 45% and more for the line treated here), thus having negative consequences in human exposure estimates, both when a new line is designed and when solutions are studied for mitigating the field generated by an existing line.