Possible damaging effects wide caused by exposure of extremely low frequency electromagnetic fields generated by high voltage overhead lines are studied. This work presents a simulation investigation of analysis the magnetic field profile produced inside 275 kV single circuit three-phase transmission line, appropriate to associate the results with international establishing limits for electromagnetic pollution. The modulations were recorded in different levels above the ground. The calculation technique of magnetic field used in this study is based on an image method and the Ampere laws. The maximum magnetic field values obtained do not exceed the limit agreed by standards that can affect the health of general population and workers. Regarding they are sufficiently lower compared to safety guidelines proposed by international organizations.