【摘要】 油纸绝缘局部放电所激发的微弱声波检测是变压器状态监测的关键挑战，现有高灵敏声传感方法因声波信噪比过低而受限。为此，文中提出一种基于梯度声学超材料的绝缘油中声信号增强检测方法，通过实现宽频带声波的压缩放大，提升微弱声波的信噪比。文中采用30个直径按二次函数增大的圆板单元构建梯度声学超材料，单元厚度为1 mm，相邻单元间隙距离保持1 mm，最小单元直径为5 mm，最大单元直径为47.05 mm，整体结构的最大尺寸小于6 cm。通过数值模拟计算该超材料的声压放大效果，结果表明，尽管超材料单元与绝缘油间有限的声阻抗差异降低了放大倍数，但拓宽了放大带宽，从而实现宽频声信号的增强。在实验中，将声传感器与超材料末端单元相结合，兼顾窄间隙声场的检测需求与超材料结构的完整性，并成功验证超材料在绝缘油中的声信号增强效果。测试结果显示，该超材料在45～200 kHz范围内具有增益效果，峰值增益可超3倍。针对针尖局部放电的实验结果表明，该超材料能直接增强检测的声波峰值，还能显著提升其在放大频段内的频率成分含量，实现对局部放电信号的有效增强检测。文中将声学超材料应用于增强局部放电声学检测，对局部放电的早期检测具有重要意义。更多还原

【Abstract】 The detection of weak acoustic waves excited by partial discharge(PD) in oil-paper insulation is considered as a critical challenge in transformer condition monitoring, while existing high-sensitivity acoustic sensing methods are constrained by the low signal-to-noise ratio(SNR) of the acoustic waves. In this paper, an acoustic enhancement detection method based on gradient acoustic metamaterial(GAM) is proposed, achieving compression and amplification of broadband acoustic waves and providing a solution for improving the SNR of weak PD acoustic signals. The GAM is constructed using 30 circular plate units with diameters increasing according to a quadratic function. The thickness of each unit is 1 mm, the gap distance is 1 mm, the minimum diameter is 5 mm, and the maximum diameter is 47.05 mm, with the overall structure’s maximum size being less than6 cm. Numerical calculations of the acoustic pressure amplification effect of the GAM reveal that although the gain factor is reduced by the limited acoustic impedance difference between the GAM and the insulating oil, the amplification bandwidth is broadened, enabling the enhancement of broadband PD acoustic signals. By integrating the acoustic sensor with the end unit of the GAM, narrow-gap acoustic field detection and structural integrity of the GAM are simultaneously achieved, and the enhancement effect of the GAM in insulating oil is demonstrated experimentally. A gain effect is exhibited by the GAM in the frequency range of 45 kHz to 200 kHz, with a peak gain factor exceeding 3. Finally, the results of needle-tip PD show that the detected acoustic wave peak is directly enhanced by the GAM, and the frequency content within the GAM amplification band is significantly improved, thus achieving enhanced detection of PD acoustic waves. This study represents acoustic metamaterials to enhance acoustic detection, which is considered highly significant for the early detection of PD.更多还原