Study On ACFM Detection Method For Weld Defect Of Cable Aluminum Jacket

Cable aluminum sheath is an important part of the structure of KV high voltage cable,which plays an important role in ensuring the safe and stable operation of the cable.Argon arc welding type cable aluminum sheath has been widely used because of the advantages of simple process,simple technology and low processing cost.The welding part of the aluminum sheath of this type of cable has the characteristics of inner wall bulge,outer wall micro-depression and axial distribution,which makes it difficult to detect the defects.The existing detection methods,such as air tightness detection,visual detection and eddy current detection,have problems such as low detection efficiency,easy to leak detection,and unable to detect the buried depth defects.Therefore,based on the principle of ACFM detection technology,this thesis designs an ACFM probe for detecting the weld defects of cable aluminum jacket,and builds a set of nondestructive detection system.Taking different kinds of defects of cable aluminum sheath weld as the research object,the detection method of cable aluminum sheath weld defect was studied.Its main contents are as follows:(1)According to the principle of AC electromagnetic field detection technology and the characteristics of the weld defect,aluminum sheath with the aid of finite element simulation software COMSOL more physical fields established the aluminum sheath delivered ACFM per input horsepower of Jane such detection of the weld defect model,through to the aluminum sheath weld area surface crack,crack,leakage welding depth(or wear)welding defects under U incentives to probe the distribution of the induced current and defect above Bz and Bx law of magnetic flux density signal analysis,the method of using simulation analysis demonstrates the aluminum sheath weld different types based on the technology of delivered ACFM per input horsepower defect detection is feasible.(2)In aluminium sheath different welding defects delivered ACFM per input horsepower to detect,on the basis of feasibility analysis,based on the aluminum sheath delivered ACFM per input horsepower weld defect detection model,the simulation analysis of the u-shaped motivate probe of rectangular coil length,width,thickness,number of turns and core two foot spacing parameters on the surface of the specimen strength of current coverage and effective incentive effects of the law;At the same time,the influence of the probe excitation frequency,current,probe lift height and different defect size(length and depth)of aluminum sheath weld on the magnetic field signal was studied by simulation analysis.(3)According to the simulation analysis results,the u-type excitation module and the orthogonal detection coil are made,and the corresponding defect detection system is built.The whole detection system includes the selection of hardware and the design of software.The hardware consists of AC signal source,signal processing module and data acquisition module.The software USES LABVIEW programming and developmentlanguage to analyze the detection signal data.Its main functions include real-time display of detection signal waveform,display of butterfly chart,defect identification alarm and storage,acquisition of detection results and playback of historical detection data.Under laboratory conditions,the physical specimens were used to test the surface cracks,buried deep cracks,and leakage(or penetration)defects.The test results show that ACFM detection technology can quickly and effectively identify the defects such as crack defect,buried depth defect,leakage weld(or weld penetration)and so on.