Acoustic sensors improve safety, reliability of hydro-generators

The primary components needed for a hydro-generator to convert flowing water into electricity are its stator winding bars. These current-carrying bars, each separated by small slot wedges for support, cut through the rotor’s magnetic field, generating an electromotive force and converting mechanical energy into electrical energy. Uneven electric fields at the slots are a safety concern and can ultimately lead to degradation, making accurate discharge detection a critical challenge Zhao et al. sought to resolve.

“After carefully studying the generator’s internal structure, we had a sudden insight: what if we could repurpose the slot wedge between stator bars into a sensor capable of detecting ultrasonic signals from discharges?” said author Ming Wu.

The researchers machined a small hole at the center of the wedge and filled it with a piezoelectric ceramic sensing material used to detect acoustic signals, optimizing the ratio of materials to enhance the sensor’s sensitivity. By introducing an artificial defect on a full-scale stator winding bar, they tested their sensor and found it well-suited for its intended application.

“The process of identifying a key engineering challenge and then devising a practical solution based on a flash of insight was truly exhilarating,” said Wu.

Because the sensor is simply an alteration to the existing slot wedge, it is easy to install in hydro-generators already in operation. The group plans to develop custom data acquisition and analysis systems, and to run pilot studies in real hydro-generators to build larger datasets for more accurate assessments of degradation conditions.

Source: “Implantable ultrasonic sensor for partial discharge monitoring in large generator stator windings,” by Yiming Zhao, Yunfei Zhang, Yankai Cui, Zhongqiang Ren, Hongxin Gong, Lisheng Zhong, Ming Wu, Xiaojie Lou, and Jinghui Gao, AIP Advances (2025). The article can be accessed at https://doi.org/10.1063/5.0283137 .