高压输电杆塔接地极作为雷电流、工频故障电流和感应电流等异常电流的关键传导通道,对于保障电力线路的安全稳定运行具有重要作用.然而,接地极腐蚀缺陷的存在将严重影响其正常的散流功能,威胁电力系统安全稳定运行,甚至人身安全.针对高压输电杆塔接地极腐蚀缺陷的远距离、小缺陷高灵敏度检测难题,该文提出一种高压输电杆塔接地极腐蚀缺陷混频 SH导波检测方法.设计了一种基于变间距永磁阵列的新型混频 SH 导波换能器结构,并通过仿真和实验验证了混频 SH 导波检测的可行性.进一步将所提方法与传统的单频 SH 导波检测方法进行比对,结果表明所提出的 SH 导波检测方法相比于传统方法对远距离、小缺陷具有更高的灵敏度检测和更好的检测效果.
Mix-Frequency SH Guided Wave Corrosion Defects Detection Method for High Voltage Transmission Tower Grounding Electrode
High-voltage transmission towers play a crucial role in the electrical power system as power transmission hubs.The transmission towers support long-distance transmission lines and serve as essential pathways for conducting abnormal currents,along with grounding devices.These towers are vital for ensuring power lines'safe and stable operation.However,the grounding electrodes of transmission towers are prone to corrosion and fracture due to imbalanced soil acidity,microbiological corrosion,and other environmental factors,which threaten the power system's safe operation.Therefore,research on detection methods for corrosion defects in the grounding electrodes of high-voltage transmission towers is necessary.However,since the grounding electrode devices of high-voltage transmission towers are typically buried underground,direct observation of the overall state of corrosion damage is not feasible.Excavation-based detection methods are labor-intensive and have low efficiency.Consequently,non-excavation-based fault diagnosis methods for grounding electrodes are essential.Ultrasonic-guided wave testing is a non-destructive method employing single-ended excitation and reception for long-distance detection and diagnosis,which is suitable for detecting corrosion defects in metal specimens like grounding electrodes that are buried underground.This method enables quick detection and localization of defects over a considerable distance.It eliminates the need for complete excavation of the grounding device,is almost immune to external electromagnetic signal interference,and can accurately identify and even quantify corrosion defects in the grounding electrode.However,electromagnetic ultrasonic-guided waves at a single frequency have limitations in detecting corrosion defects in grounding electrodes.Low-frequency guided waves propagate over long distances with minimal attenuation but lack sensitivity in detecting microdefects.On the other hand,high-frequency guided waves exhibit high sensitivity to microdefects but suffer from significant attenuation and weak echo signals during long-distance detection.Based on variable-spacing permanent magnet arrays,this paper proposes a mixed-frequency SH-guided wave testing method for detecting corrosion defects in high-voltage transmission tower grounding electrodes.An electromagnetic ultrasonic guided wave transducer(EMAT)structure is designed with a variable-spacing permanent magnet array.The mixed-frequency SH-guided wave transducer includes three groups of periodic permanent magnet arrays with different spacings.A runway-shaped coil is positioned beneath,creating low-frequency,mid-frequency,and high-frequency guided wave excitation zones sequentially concerning the tested grounding electrode specimen.This setup enables the simultaneous excitation of low-frequency,mid-frequency,and high-frequency SH-guided waves.The mixed-frequency guided wave echoes from the corrosion defect in the grounding electrode are further processed to adaptively identify defects at different distances and sizes.This method and the traditional single-frequency SH-guided wave testing approach are compared,demonstrating superior detection sensitivity and improved performance in detecting long-distance and microdefects.Overall,the mixed-frequency SH-guided wave testing method presents a promising solution for enhancing the efficiency and accuracy of corrosion defect detection in high-voltage transmission tower grounding electrodes.
High voltage transmission towersground electrodeelectromagnetic acoustic guided wavesfrequency-mixing SH wavesdefect detection
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