The Role Played by Current Phase-shift on Magnetic Field Established by AC Double-Circuit Overhead Transmission Lines - Part I: Static Analysis

Ac double-circuit overhead transmission lines may exhibit large phase-shift angles between current phasor terns of the two circuits. Here a static analysis (relevant to single time instants or constant load conditions) of the role played by such phase-shift on the magnetic field established by these lines is performed, showing that the phase-shift angle interacts with phase conductor arrangement, resulting in a wide variety of field profiles at a given line section. The analysis, carried out for two tower topologies and several couples of rms current values, reveals interesting general features of field profiles that depend only on phase-shift angle. This proves that neglecting, or even misunderstanding, current phase-shift effects for ac double-circuit overhead transmission lines can lead to severe errors in field calculation, that may have negative consequences on human exposure estimates, both at the design stage of new lines and at the rearrangement stage of existing lines.