This paper presents a model to calculate the voltage induced by lightning in electrical distribution lines. The model is based on a spectral analysis of electromagnetic fields (EMF) caused by lightning circumscribed to the spectral content of Lightning Electromagnetic Pulse (LEMP). To modeling the lightning is used the traditional focus of the short monopole antenna and the LEMP is analyzed using Fast Fourier Transform FFT. The induction source is the azimuthal magnetic field. The maximum impact distance (D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ) is estimated using the value of induced voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ind</sub> ) The induced voltage in the maximum impact distance exceeds the value of critical flashover voltage (CFO) and it is just at that point on the line where failure might take place.