The permeance of the magnetic circuit is defined as the reciprocal of the reluctance. Permeance = 1/Reluctance It is defined as the property of the magnetic circuit due to which it allows the flow of the magnetic flux through it. Permeance is analogous to conductance in an electric circuit.
While estimating the overhead lines, the first and last pole is always earth connected and after every 3rd electrical pole, the fourth pole is earthed. Therefore, the approximate number of required ground set = 4