Partial discharge detection in HV and MV terminations with fiber optic sensors

Abstract

This study presents a novel approach to detect partial discharges (PD) in a medium-voltage (MV) cable termination using fiber optic-based acoustic PD sensors. The sensing system is designed by the company Optics11. It is a commercial off-the-shelf product under the trademark name of OptiFender, which uses non-metallic, passive fiber opticbased acoustic sensors, which are galvanically isolated. Given these properties, OptiFender sensors can be installed directly on the cable accessories. The sensors can withstand the curing conditions of the filling compound used in the cable accessories, making them suitable for both retrofitting and embedding applications. In this study, defect terminations with PD were investigated. Several OptiFender sensors were installed all around the defect termination, and all of them could detect partial discharge with a sufficient signal-to-noise ratio (SNR). The termination was operated at medium voltages, with PD levels of from a few pC up to around 100 pC, but the application of OptiFender is not limited to only medium voltages, and there have been examples of using the same sensors at voltages of up to 400 kV. All the sensors picked up PD with a high SNR. Acoustic PD sensors provide an indirect measure of the PD activity by measuring the released energy of the partial discharge in the acoustic domain, rather than the traditional direct measurement of the displaced charge. The OptiFender system can provide uninterrupted, continuous, and unsupervised monitoring of electrical assets for both indoor and outdoor applications.