基于同步压缩小波变换的接地扁钢缺陷电磁超声SH导波检测方法

Electromagnetic ultrasonic SH guided wave detection method for grounded flat steel defects based on synchrosqueezed wavelet transforms

接地网对电力系统的可靠运行起到至关重要的作用,然而,接地网的埋地环境使得接地装置易产生缺陷,因此需要及时开展接地网的检测。该文针对电力系统接地扁钢,提出基于线性调频激励和同步压缩小波变换的SH导波检测方法。首先,设计了永磁体阵列SH导波换能器,该换能器结构简洁,适合用于扁钢结构。其次,使用线性调频信号激励换能器,研究了同步压缩小波变换,在时频平面对导波重叠信号进行辨识,有效区分了不同缺陷以及端面。随后,利用有限元仿真和试验,验证所提出信号分析方法,计算得到的距离定位误差均在3%以内,证明了该方法可以对导波走时进行准确提取,对缺陷高精度定位。最后,和短时Fourier变换、Wigner分布的结果进行比较,验证了同步压缩小波变换高时频聚集性的优势。

The grounding grid plays a vital role for ensuring reliable power system operations. However, the buried environment around the grounding grid can result in grounding device defects, so the grounding grid must be periodically tested. This paper presents a SH guided wave detection method based on linear frequency modulation excitation and synchrosqueezed wavelet transforms for grounded flat steel power systems. The system uses a permanent magnetic array SH guided wave transducer which is simple and suitable for flat steel structures. The transducer is excited with a linear frequency modulation signal with synchrosqueezed wavelet transforms used to analyze the signal. Identification of the overlapping guided wave signals in the time-frequency plane effectively distinguishes between various defects and end faces. Signals from finite element simulations and experiments were then used to evaluate the signal analysis method. The calculated distance errors were all within 3%, which shows that the method can accurately extract the guided wave travel times and accurately locate defects. Comparisons with results using short-time Fourier transforms and Wigner distributions show the advantages of the time-frequency aggregation of the synchrosqueezed wavelet transforms.