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Acoustic Detection of Partial Discharges with an Optical Fiber Interferometric Sensor

Author(s): Carlos MACIA-SANAHUJA, Horacio LAMELA, Jesús RUBIO, Daniel GALLEGO, Julio POSADA, Jose A. GARCIA-SOUTO
Affiliation(s): Grupo de Optoelectronica y Tecnologia Laser, Universidad Carlos III de Madrid

Topic: 7. Fiber Optical Sensors
Presentation: Oral

An optical fiber interferometric sensor with intrinsic transducer along a coil of the fiber is presented for the acoustic detection of partial discharges within oil-filled power transformers. The sensor is designed for measurements of high sensitivity in a harsh environment of electrical discharges, temperature drift and in oil immersing. The partial discharges produce much attenuated ultrasonic signals (~1 Pa) that are detected by the sensor immersed in oil with the purpose of localizing the source into the transformer. The transducer size is 28mm of diameter and 28mm of length. The ultrasonic frequencies are detected in the range of 20 kHz – 200 kHz. We report the results of characterization of the optical-fiber probe immersed in an acoustically isolated chamber and compared with the response of piezoelectric ultrasonic transducers. They confirm that the performance of the interferometric sensor is better with lower frequencies. Finally, we demonstrate on-site measurements with the first results in a controlled experiment of partial discharges generation (100pC – 1000 pC), electrical detection and acoustic detection with piezoelectric external sensors. The results show that the partial discharges are directly measured with the optical fiber interferometer, instead of the indirect techniques actually available in the transformer walls.