Common-mode interference voltages are also referred to as asymmetrical interference voltages.
They occur between the conductors in a cable and a defined reference point (remote earth, reference ground). They stress the conductor isolation to the reference point. Common-mode interference voltages are mainly caused by potential differences in the earthing network of an installation resulting from earth compensation currents (fault currents, lightning currents). They can, however, also be injected by magnetic interference fields. With transmission path structures not balanced to ground, part of the common-mode interference voltage is always converted into a
normal-mode interference voltage.
