A device for recovering electrical energy includes a ferromagnetic cable helically wound around a portion of a power conductor , and disposed to form both a magnetic system which is capable of sensing the magnetic field induced by a current passing through the power conductor , and a way to generate a utilisable induced voltage from this magnetic field. The ferromagnetic cable is produced from an assembly of unitary strands produced from ferromagnetic material, these strands being assembled into the form of a stranded wire, each unitary strand behaving as a winding in which the induced voltage is induced, and the assembly of unitary strands forming an assembly of windings connected in parallel by way of connecting terminals provided at the ends of the ferromagnetic cable to recover the induced voltage.