Overhead and cable power transmission lines magnetic field strength estimation al- gorithm is presented. Example of 500 kV overhead transmission line power frequency MF strength distribution is presented in comparison with 500 kV cable transmission line MF distributions. Ac- cording with the problem of general public electromagnetic safety maintenance is suggested the optimal circuits’ arrangement with changed order of the phases that allow reducing the 50 Hz MF values to maximal permissible levels (hygienic standards of general public exposure). It is shown that multiphase sources create the field of elliptic polarization, which most root- mean square strength value is on the ellipse major axis, whereas result values calculation by components with Pythagorean Theorem use lead to errors with the increase of real value to 41%. By the example of 500 kV lines is shown the differences between results of the applied calculation methods. For 500 kV cable lines the ways of MF value decrease to permissible levels under different kinds of it lying are examined. There is shown that socket joint use with cables and its locations in the corners of equilateral triangle under correctly changed order of the phases as well as slight increase of cable depth gives the possibility to avoid the ferromagnetic screens arrangement, and to cut costs.