Efficiency of cable lightning protection by wire

An existing method of calculation of protective wires shielding factor is not accurate, as it takes into account only inductance of cable and protective wires without of active resistance. In fact at the front of wave the current of a lightning is allocated between a cable and a protective wire mainly in inverse proportion to inductive resistance, on decay of a wave it is divided in inverse proportion to their active resistance. There are some corrections to a method that is in use, which are discussed in this paper