MODELLING AND DEVELOPMENT OF EXPONENTIAL HORN-ASSISTED FIBER-OPTIC SENSOR FOR PARTIAL DISCHARGE MONITORING IN HV SUBSTATIONS

Abstract

Partial discharge (PD) is considered as an important marker of insulation deterioration of high voltage (HV) apparatus. Therefore, PD monitoring is crucial for ensuring the sound and safe operation of high-voltage (HV) substations. In this work, an optical fiber-based, sensitive, and simple acoustic PD sensor module is proposed, which introduces a fiber-to-fiber coupling arrangement placed at the internal focal region of a suitably modelled exponential horn-shaped waveguide. The exponential horn concentrates the PD-generated ultrasonic pressure waves, thereby amplifying the acoustic emission and resulting in a larger impact at the focal point. These impacts cause small transverse misalignments between the transmitting and receiving optical fibers of the fiber-to-fiber coupling arrangement, which alter the coupling efficiency and result in measurable changes in the intensity of the coupled light. This intensity-modulation scheme eliminates the need for sophisticated optical components, such as fiber Bragg gratings or tunable lasers, resulting in a cost-effective and compact system suitable for installation in substations for monitoring PD events. The horn-assisted sensor offers a better signal-to-noise ratio and a broader detection bandwidth, which would otherwise be challenging. Furthermore, the performance of the proposed sensor is compared with the standard IEC 60270-based electrical detection system in the laboratory, which confirms the comparable detection capability of the proposed method. The system demonstrates reliable performance even in the presence of significant electromagnetic interference, making it suitable for identifying early-stage PD activity across air, oil, and solid insulation. The findings suggest that the introduced horn-guided fiber-optic sensor holds great potential for real-time partial discharge monitoring and evaluating the condition of high-voltage substation assets.