XJTU Develops High-Sensitivity Piezoelectric Film Sensor for Generator Partial Discharge Monitoring

Recently, the research team of Professors Jinghui Gao and Lisheng Zhong at Xi'an Jiaotong University has developed an embedded piezoelectric thin-film ultrasonic sensor for highly sensitive real-time monitoring of ultrasonic signals caused by partial discharge in generator stator windings.The sensor employs a PZT piezoelectric thin film and enhances sensitivity through increased electrode area.The related research findings have been published in the journal High Voltage under the title "Developing Implantable High-Sensitivity Piezoelectric Thin-Film Sensor to Monitor Partial Discharge of Generator Stator Windings".

In this study, the developed sensor utilizes a PZT piezoelectric thin film—deposited on a Pt/Si substrate via the sol-gel method.The piezoelectric film features a thickness of 1.5 μm, with 3-mm-diameter Pt top electrode arrays fabricated by magnetron sputtering.Assuming ultrasonic signals act as uniform pressure waves, increasing the sensor's wave-receiving area enhances the ultrasonic-excited charge output, thereby improving sensitivity during signal amplification with a charge amplifier.

High-Sensitivity Implantable PZT Thin-Film Sensor Fabrication

To compare sensitivity and optimize partial discharge monitoring, this study fabricated two embedded PZT piezoelectric thin-film sensors: one with a single top electrode (single-point sensor) and another with two top electrodes (two-point sensor).The final packaged sensor (taking the two-point sensor as an example) is a compact 2 cm × 2 cm square with a thickness of only 1 mm.This ultra-compact piezoelectric thin-film ultrasonic sensor can be directly embedded onto generator stator winding surfaces, enabling detection of ultrasonic signals from partial discharges near the acoustic source.This capability enhances the accuracy of generator insulation condition assessment, providing a valuable tool for improving power system reliability and security.

In tests using pencil lead breaks on a polyethylene plate as the ultrasonic source, the two-point sensor detected a peak-to-peak value nearly twice that of the single-point sensor, demonstrating that increased electrode area effectively enhances sensor sensitivity.The two-point sensor demonstrates significantly higher sensitivity than both broadband sensors and flexible polyvinylidene fluoride (PVDF) sensors.The embedded PZT piezoelectric thin-film sensor achieves a frequency detection limit of 80 kHz for pencil lead break signals, compared to 30 kHz for both broadband and PVDF sensors.The full-scale generator experiment verified the sensor's high-fidelity detection of partial discharge signals, underscoring its potential for enhanced insulation condition monitoring in power systems.

Pencil Lead Break Test of the Embedded PZT Piezoelectric Thin-Film Sensor

By detecting pencil lead break signals, four sensors were compared across three dimensions: (a) time domain, (b) frequency domain, and (c) peak-to-peak values. (d) Sensitivity comparison of single-point, two-point, and broadband sensors across 10-1000 kHz.

To demonstrate the superiority of the embedded PZT piezoelectric thin-film sensor in detecting ultrasonic signals from partial discharges in generator stator windings, researchers established a full-scale experimental platform.

Partial Discharge Test Rig for Generator Stator Windings

Partial discharge signals from winding detected by two-point and broadband sensors, compared in (a) time domain and (b) frequency domain; (c) Typical acoustic partial discharge signals detected by both sensors during half power frequency cycle.

In summary, researchers have developed and validated an embedded high-sensitivity PZT piezoelectric thin-film ultrasonic sensor for precise monitoring of partial discharge signals in generator stator windings.Pencil lead break tests on polyethylene boards demonstrated that the PZT piezoelectric thin-film sensor with extended electrode area achieves higher sensitivity and broader frequency response compared to conventional ceramic- and PVDF-based ultrasonic sensors.Full-scale experiments confirm its capability for high-fidelity detection of partial discharge-induced ultrasonic signals while remaining immune to electromagnetic interference.These results underscore the sensor's potential to enhance insulation condition assessment and fault diagnosis in power generation systems, contributing to improved operational reliability and safety.

Citation: China Electronic Components Association.

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