| With the promotion of the construction project of the Nationwide Network Connection,Mutual Supply South and North,and Power Transmitted from West to East,the interconnection degree of transmission lines in China is getting more and more intensive,and the transmission mileage is increasing sharply.It is of great significance to find the defects in transmission lines early by using quick and effective detection methods to ensure the safe and stable operation of transmission lines.Infrared,visual and eddy current detection methods are often used to detect the defects of power transmission lines.However,the existing detection methods have some limitations.In this paper,based on theoretical calculation,computer simulation analysis and experimental test,an axial eddy current rapid detection method of aluminum strand defects is proposed for the detection of cracks and broken strands in the outer layer of aluminum strand of transmission lines.This method is expected to be used for rapid detection of aluminum strand defects in the state of power failure.The specific content of the paper includes the following aspects:(1)Theoretical study on axial eddy current testing for defects of aluminum stranded wire.The circumferential flow vortex generated by the traditional external coil and the axial vortex simulation model proposed in this paper were established.According to the structural characteristics of the outer aluminum strand of the transmission line,the disturbance law of the eddy density caused by the defects of the aluminum strand under the two excitation modes was analyzed.At the same time,respectively to extract aluminum conductor under two kinds of incentives in the absence of any defect on the surface of eddy current density and use it as a reference point,is used to eliminate the interference of aluminum conductor surface uneven,expressed in the detection signal and reference signal difference defect size,through the comparison of these two incentives detection effect found,this paper puts forward that the axial eddy current testing method has higher detection sensitivity.(2)Probe design and parameter optimization.In order to further improve the detection sensitivity of the designed probe,an axial eddy current test model of aluminum strand was established by using simulation software,and the model parameters were optimized.The influence of the length and thickness of the excitation coil and the variation of the length and width of the detection coil on the peak value of the differential signal of the eddy current probe is studied.In addition,through the simulation analysis of the characteristic signal of aluminum strand crack and broken strand defect,the classification and recognition method of the crack and broken strand defect is put forward.(3)Test system design and experimental analysis.Based on the axial eddy current detection method proposed in this paper and the designed probe,combined with the actual detection requirements of power transmission lines,the array axial differential eddy current probe and the corresponding power transmission line detection device are designed and manufactured.The experimental test platform of power transmission line damage was built.Then the consistency and detection range of each detection unit of the probe are verified,and the transmission lines with cracks of different depths and broken strands are tested and analyzed.Experimental results show that the thesis design the transmission axis to the eddy current testing probe the locations of transmission line circumferential crack defects with good detection effect,can effectively detect the minimum radial depth of 0.4 mm crack defects,which can effectively identify cracks,defects,fully verified the axial eddy current testing method for defect detection of transmission line,feasibility and the effectiveness of the designed new type array eddy current probe.In conclusion,the axial eddy current detection method proposed in this paper can be used for the rapid detection of transmission line defects. |
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