Simple calculation method of the magnetic field from double-circuit twisted three-phase cables as a tool for fault detection

This paper proposes a simple innovative formula for the calculation of the magnetic field generated by a single and a double circuit twisted three-phase power cable line. The formula results a good approximation of the rigorous analytical one and at the same time is much more accurate than the approximated formula found in literature, as demonstrated by the case of a twisted three-phase power cable used for power distribution at the medium voltage level. The effectiveness of this simple innovative formula is examined in the case of a double-circuit twisted three-phase power cable line following the ‘worst case’ approach and we propose an approximate expression for the total magnetic field generated by both twisted three-phase power cables that can be used as a diagnostic tool in fault detection algorithms, as the magnetic field can provide useful information on the phasors of the currents flowing through the conductors.