This work describes the results obtained of the analysis of the pattern of stationary wave of a dielectric circular waveguide with plasma inner to low pressure to study the channel of communication in the plasma of the corona effect in the lines of transmission of electric power. By means of the equation of standing wave, there are found the constants of attenuation and of phase of the plasma that fills the dielectric waveguide. Finally there are discussed the possible test in real installation and the applications of this method.