This paper aims to explore the feasibility of mitigating the field generated by HV underground three-phase balanced power lines, by the use of passive non-compensated and compensated loops. In particular, the analysis has focused on the flat single circuit configuration, and has been carried out in a systematic way, obtaining for every configuration analysed (single loop, three-conductor arrangement and double loop arrangement) the optimum location of compensating conductors, the mitigation performance of several copper sections, the optimum capacitance of the compensated loop and the performance when multiturn coils are used.