Evaluation of the Frequency Information Contained in PD Signals for Localization in Power Cable Monitoring

Abstract:
One of the main challenges for grid operators is to maintain a reliable and sound power grid. Especially in case of power cables, partial discharges (PDs) can lead to a deterioration of the solid insulating materials, ultimately resulting in an insulation breakdown. Thus, the measurement and the monitoring of partial discharges can yield indicators to evaluate the insulation condition of power cables. While PD measurements serve as diagnostic tool to identify and localize the weak spots in the insulation system, monitoring systems are used to identify changes under operating conditions. Thus, the main purpose of a monitoring system is to signal the emerging presence of PDs, while localization information can be seen as an additional feature. In order to generate localization information, some kind of time synchronization is usually required. This can be complex in terms of system architecture as well as cost intensive. Also, the installation of a system with multiple units might be required instead of installing a few stand-alone monitoring devices at particular joints or terminations. Besides gathering localization information by using the time of flight information, the frequency information contained in a PD pulse presents an option to coarsely evaluate the position of a PD source. This paper presents a prototypical design for a stand-alone monitoring device that uses the frequency component to gather localization information. A validation of this principle is given by evaluating measurements of an artificial PD signal.