The paper illustrates the experience acquired by CESI and ENEL in studying and designing technical solutions to reduce the magnetic field generated by high voltage (HV) and extra-high voltage (EHV) overhead lines and underground cables. In particular, after a brief description of the various "mitigation" methods characterised by the research on the subject, the paper will be focused on the main techniques for possible application to existing installations, since they represent the real challenge a power line operator may encounter.