Abstract
A fiber optic interferometric sensor with an intrinsic transducer along a length of the fiber is presented for ultrasound measurements of the acoustic emission from partial discharges inside oil-filled power apparatus. The sensor is designed for high sensitivity measurements in a harsh electromagnetic field environment, with wide temperature changes and immersion in oil. It allows enough sensitivity for the application, for which the acoustic pressure is in the range of units of Pa at a frequency of 150 kHz. In addition, the accessibility to the sensing region is guaranteed by immune fiber-optic cables and the optical phase sensor output. The sensor design is a compact and rugged coil of fiber. In addition to a complete calibration, the in-situ results show that two types of partial discharges are measured through their acoustic emissions with the sensor immersed in oil.
Highlights
Oil-paper insulation systems are commonly used in power apparatus such as power transformers and high voltage cables, among others
Techniques such as dissolved gas analysis (DGA) electrical measurements of high frequency transients (HF-VHF), detection of electromagnetic signals generated in the UHF band and ultrasound acoustic emissions (AE) detection are used for this propose
A fiber optic sensor for Partial discharges (PD) detection in transformer oil has been developed. It has been characterized in an acoustic test bench in water and tested with real PD generated in oil
Summary
Oil-paper insulation systems are commonly used in power apparatus such as power transformers and high voltage cables, among others. The sudden release of energy caused when a PD occurs produces a number of effects like chemical and structural changes in the materials, electromagnetic signal generation and acoustic emissions (AE) [4] These induced effects are used for its detection. Techniques such as dissolved gas analysis (DGA) electrical measurements of high frequency transients (HF-VHF), detection of electromagnetic signals generated in the UHF band and ultrasound AE detection are used for this propose. Among these techniques AE ultrasound detection offers great advantages such as the possibility of on-line testing and the ability to locate where PD activity is occurring, which is helpful in large test objects like power transformers.
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