Research on the Partial Discharge Characteristics of Transformers Under Multiple Types of Voltages Based on DFB Fiber Ultrasonic Sensors

To investigate the partial discharge (PD) characteristics of transformers under different test voltages (power frequency, lightning impulse, and operating overvoltage), this study utilizes DFB fiber-optic ultrasonic sensors to examine the acoustic signal characteristics of PD in an 80 kVA oil-immersed transformer under various voltage types. The experiments reveal that power frequency discharges exhibit short durations in the time domain, with high-frequency components concentrated between <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$50-200 \text{kHz}$</tex> in the frequency domain. Operating overvoltage discharges manifest as dense and chaotic pulse clusters in the time domain, lasting the longest, with low-frequency components concentrated between <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{2 0 - 1 0 0}$</tex> kHz in the frequency domain, and the time-frequency diagram shows uniformly distributed frequency components with slow attenuation. Lightning impulse discharges appear as distinct pulse clusters in the time domain, with the highest amplitudes, and their frequency domain spans <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0-300 \text{kHz}$</tex>, where the lowfrequency band exhibits the highest energy, while highfrequency components remain relatively flat. These findings provide an important basis for a deeper understanding of transformer PD characteristics and ensuring the safe and stable operation of power systems.