Identification and Detection of Defect in Metal Casing

Based on the propagation rules of electromagnetic waves in metal conductors, this paper analyzes the characteristics of electric field and magnetic field of internal conductors. Then the complex power of electromagnetic wave is calculated. The impedance calculation formula of metal conductor is derived. Moreover, in order to identify and detect defects of metal casing, an alternating current impedance measuring method for the metal casing is proposed by changing the alternating current frequency. Furthermore, a three-dimensional metal casing model is built in COMSOL. Both the electric field and magnetic field are numerically calculated for non-defective and defective casing separately. Meanwhile, the influence of casing defects on the electric field and magnetic field is analyzed. Finally, simulation and measurement results show that: casing defects can be quantitatively detected and effectively located by measuring the alternating impedance of the metal casing.