The non stopping growth of urban centers and increasing demand for electrical energy causes more high voltage lines and underground cables installed in cities. As a direct consequence, the generation of Magnetic Fields (MF) is increased due to the new power lines and cables. Magnetic Fields have raised concerns in the population for years by its association with possible health effects. Before building new facilities it is necessary to assess whether these would meet the requirements of the regulations. Thus it is necessary to have tools that quantify the MF values emitted by the planned facilities. In the laying of cables, two zones are identified. The first one is where the phases are regularly laid close to each other. The other area is where the joints are made. In this area is where the distances between phases are higher. In the latter, the magnetic field values are higher due to the increase of the separation.