Comparative analysis between impulsive detection methods applied on partial discharge acoustic signals

IEEE IMTC

Partial discharges (PD) plays an important role on power transmission lines and equipment failures therefore previously detect this high-voltage phenomena can prevent severe damages and avoid further outlay. Spark gaps discharges are between the most common PD in power transformers and other efficiency energy equipment. And in order to detect this effect optical and acoustic sensors are normally employed into monitoring systems. However optical sensors are expensive for transmission power lines and detecting acoustical signals from PD can be difficult since they are normally followed by other background sounds. In order to improve detection sound systems in this work we compare two methods that are regularly used on impulsive signal processing, the Variance Method (VM) and the Conditional Median Filter (CMF), to detect PD acoustic signals. From the presented results it is observed that the CMF is more appropriated for detecting impulsive PD although the VM detected less false positive discharge and can still be further optimized.

Images from high-voltage impulse discharges evaluated with 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.