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We report on the successful application of distributed acoustic sensing (DAS) to the detection of partial discharge (PD). A detection limit of about 1 nC discharge magnitude was achieved for PD in a real-scale model of a high voltage termination. Dedicated ultrasonic fibre-optic transducers were interrogated using coherent optical time-domain Rayleigh backscatter reflectometry (C-OTDR). Random quadrature demodulation was employed for retrieving relevant acoustic information from the raw C-OTDR backscatter traces. To our knowledge, our results are a first-time demonstration that quasi-distributed fibre-optic acoustic sensing is a candidate technology for the acoustic partial discharge monitoring of power cable joints and terminations.
Partial discharge in elastomeric high voltage insulations is a major reason for device failure. The special challenges of the high voltage environment limit the use of conventional acoustic emission sensors. Fibre-optic sensors can cope with these challenges thanks to their optical sensing principle and the use of all-dielectric materials. In this contribution, improvements to a previously introduced design of ultrasonic fibre-optic acoustic partial discharge sensors for elastomeric insulations are presented. The improved performance of fibre-optic acoustic sensors in detecting AC partial discharge is demonstrated. Furthermore, their ability to detect low-level damage processes in elastomeric insulation under DC dielectric stress is shown to outperform the highly sensitive electrical detection method.
Recent progress in the development of ultrasonic fibre-optic sensors for detecting acoustic emission from partial discharge in elastomeric insulations is presented. These sensors are an important part of a proposed comprehensive scheme for the fibre-optic monitoring of cable accessories. After specifying the underlying design goals the improved fibre-optic sensor design is outlined. It is experimentally shown that it offers about ten-fold improvement over a previously investigated resonant cantilever-type design in terms of detection limit, making it competitive with conventional piezoelectric transducers, however with the added compatibility with strong electrical fields and electromagnetically noisy environments.
In high-voltage facilities of power stations and transmission networks, discharge activities leading to catastrophic failure can occur. Early detection of partial discharges (PD) in polymeric insulations of HV cable terminations and joints is therefore increasingly important. This paper describes a monitoring methodology to detect PD activity in silicone elastomer by two independent fibre-optic sensor types. Fluorescent fibre-based sensors are sensitive to plasma optical emission already at the onset of PD while an acoustic fibre-optic sensor responds to acoustic emission from the PD during its progression. The sensitivities of both sensor types are compared, and it is demonstrated that they provide complementary information for fibre-optic sensor-based monitoring of high-voltage cable accessories.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.