Abstract
Partial discharge detection is crucial for electrical cable safety evaluation. The ultrasonic signals frequently generated in the partial discharge process contains important characteristic information. However, traditional ultrasonic transducers are easily subject to strong electromagnetic interference in environments with high voltages and strong magnetic fields. In order to overcome this problem, an optical fiber Sagnac interferometer system is proposed for partial discharge ultrasound detection. Optical fiber sensing and time-frequency analysis of the ultrasonic signals excited by the piezoelectric ultrasonic transducer is realized for the first time. The effective frequency band of the Sagnac interferometer system was up to 175 kHz with the help of a designed 10 kV partial discharge simulator device. Using the cumulative histogram method, the characteristic ultrasonic frequency band of the partial discharges was between 28.9 kHz and 57.6 kHz for this optical fiber partial discharge detection system. This new ultrasound sensor can be used as an ideal ultrasonic source for the intrinsically safe detection of partial discharges in an explosive environment.
Highlights
The online monitoring and positioning of partial discharges (PD) is very important for the state maintenance of power appliances
The PD process is always accompanied by ionization, thermal radiation, acoustic emission, photon emission and other physical phenomena [1], and it includes a chemical reaction resulting in SF6 and other gases [2]
The electrical detection methods include the pulse current method, ultra-high frequency detection method, dielectric loss analysis method, and radio interference voltage method [3,4,5,6,7], which are susceptible to electromagnetic interference and may be the cause of pollution to the power grid and power equipment
Summary
The online monitoring and positioning of partial discharges (PD) is very important for the state maintenance of power appliances. There are several major types of fiber-optic acoustic sensors that have been developed recently, including the diaphragm-based Fabry–Perot interferometric (FPI) sensors [15,16,17], fiber Bragg grating (FBG)-based sensors [18,19], Sagnac interferometric sensors [15,20,21,22], and fiber laser-based interferometric sensors [23,24] These types of sensors, depending on their structure, have different sensing performances in terms of the sensitivity and frequency response, and have different applicability, such as being capable of being placed inside or outside transformers, or both [20,25,26]. Different fiber coils could be simultaneously used for the detection of components with different characteristic frequencies of PD ultrasonic signals in order to enhance the detection performance of PD signals
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