Images from high-voltage impulse discharges evaluated with a developed graphical software

Power transmission lines are constant targets of high electrical discharges such as corona and lightning. This last is manly characterized as a high impulse voltage, which can rapidly cause severe damages to equipment in the lines. Therefore, detect the amplitude of these discharges in power lines is critical for the proper design of protective systems. Recently an impulse voltage sensor based on electret films was presented. The sensor employs a spherical electrode in direct contact with a grounded thin electret film. Whenever a negative electrical impulse voltage is applied on the spherical electrode, partial discharges occurs all around the electrode forming a circular pattern that can be visualized if toner is spread over the film. Depending on the discharge amplitude circles with larger diameter are formed. In this paper we present a software implementation through which the discharge images with circular patters can be measured and direct correlated to the impulse discharge amplitude, providing a reliable and fast method for measuring electrical discharges in the field. The software was validated performing measurements of the images diameter and correlating it with well defined discharges amplitude.