基于磁导率锁定放大的高压输电线压接结构内部钢管探测
Internal Steel Pipe Detection in High-Voltage Transmission Line Compression Joints Based on Permeability Locked-In Amplification

为解决高压输电线压接结构内部钢管检测中X射线法设备笨重、存在辐射的难题，本文提出一种基于磁导率锁定放大的无损检测方法。设计了由硅钢铁芯和激励–检测线圈构成的专用磁导率探头，用于提取内部钢管的磁特性变化；开发了以正交锁定放大为核心的微弱信号处理电路，通过开关解调和低通滤波从强噪声背景中提取信号的正交分量，进而计算幅值与相位。以LGJ-400/35型输电线压接结构为对象的实验表明：该系统噪声低于50 mVpp，能清晰识别钢管位置，定位精度优于10 mm；所研制的便携系统总重仅2.9 kg，较传统X射线设备(通常13~40 kg)大幅减轻。本研究为高压输电线压接质量检测提供了一种轻量化、高精度的有效解决方案，有助于推动线路巡检自动化发展。
To address the challenges of heavy equipment and radiation exposure associated with X-ray inspection of internal steel pipes in high-voltage transmission line compression joints, this paper proposes a non-destructive testing method based on permeability locked-in amplification. A specialized permeability probe, consisting of a silicon steel core with excitation and detection coils, was designed to extract magnetic characteristic variations from the internal steel pipe. A weak signal processing circuit, centered on orthogonal lock-in amplification, was developed to extract the quadrature components of the signal from a high-noise background through switching demodulation and low-pass filtering, enabling the calculation of signal amplitude and phase. Experiments conducted on LGJ-400/35 transmission line compression joints demonstrated that the system exhibits noise below 50 mVpp, enables clear identification of the steel pipe location with a positioning accuracy better than 10 mm, and the developed portable system weighs only 2.9 kg, significantly less than traditional X-ray equipment (typically 13~40 kg). This research provides an effective, lightweight, and high-precision solution for quality inspection of high-voltage transmission line compression joints, facilitating the advancement of automated line inspection.