Due to the electrical, thermal, and mechanical stress, the insulating materials of cable undergo a slow aging process in service, which leads to the decline of insulation performance. Besides, friction frequently occurs when the cable is moving or vibrating, which will easily cause mechanical damage including frays and chafes. Both aging and damage will cause the characteristic impedance to change. Therefore, it is of great significance for the safe operation of the cable to analyze the variations of characteristic impedance and to make an effective diagnosis. In this article, a two-dimensional model of the cable containing defects is first built, and the characteristic impedance of the model is calculated by the finite-element method (FEM). Meanwhile, a quantitative analysis of the characteristic impedance under two defect types is carried out. Second, combining the space-time focusing of time-reversal and the time-frequency characteristics of reflectometry, the time-reversal time-frequency domain reflectometry (TRTFDR) is proposed to diagnose the cable faults. Based on the distributed parameters calculated by the FEM, the TRTFDR simulation model is established to study the judgment of different faults. Finally, the validity of this method is verified by experiments.

The physical properties in amorphous regions are important for the insulation aging assessment of polytetrafluoroethylene (PTFE) cable insulation materials. In order to study the effect of boron nitride (BN) nanoparticles on the physical properties of PTFE materials under moisture, temperature, and electric fields conditions at the molecular level, the amorphous region models of PTFE, BN/PTFE, water/PTFE, and water/BN/PTFE were respectively constructed by molecular dynamics (MD) simulation. The mechanical properties including Young’s modulus, Poisson’s ratio, bulk modulus, and shear modulus, along with glass transition temperature, thermal conductivity, relative dielectric constant, and breakdown strength of the four models have been simulated and calculated. The results show that the mechanical properties and the glass transition temperature of PTFE are reduced by the injection of water molecules, whereas the same, along with the thermal conductivity, are improved by incorporating BN nanoparticles. Moreover, thermal conductivity is further improved by the surface grafting of BN nanoparticles. With the increase of temperature, the mechanical properties and the breakdown strength of PTFE decrease gradually, whereas the thermal conductivity increases linearly. The injection of water molecules increases the water content in the PTFE materials, which causes a gradual increase in its relative dielectric constant. This work has shown that this effect is significantly reduced by incorporation of BN nanoparticles. The variation of physical properties for PTFE and its composites under the action of moisture, temperature, and electric fields is of great significance to the study of wet, thermal, and electrical aging tests as well as the life prediction of PTFE cable insulation materials.

Cables, transmitting both power and signal, are essential in electric power systems. Due to the combined effect of electromagnetic and thermal fields, cable insulation aging starts from the destruction of polymer molecular structure and deteriorates in the form of insulation defects, resulting in the degradation of cables eventually. In this article, multiscale simulation is implemented to comprehensively analyze the insulation aging mechanism and reveal the variation law of aging characteristics. Regarding multiscales, by molecular dynamics (MD) simulation and finite-element method (FEM), the material and electrical parameters are calculated and quantitatively analyzed. According to the findings, tiny molecular products resulting from thermal and electrical aging are the main causes of dielectric constant and electrical conductivity variations. Field distribution inside the cable is distorted due to the degradation of material parameters, thus changing power loss and electrical parameters. The multiscale analysis method in this article can make the cable insulation aging analysis more time- and resource-efficient, providing the theoretical basis and data support for cable fault diagnosis and remaining useful life prediction.

Given the critical role of aviation cables in aircraft electrical systems, accurately predicting their lifetime and devising effective preventive maintenance strategies are essential for ensuring flight safety and reducing maintenance costs. This article proposes a preventive maintenance strategy for aviation cables based on lifetime prediction under variable operating conditions. Firstly, an electromagnetic-thermal field coupling simulation is conducted to establish a mapping relationship between conductor temperature, current, and ambient temperature. This relationship is then utilized to construct an analytical model of conductor temperature using multiple linear regression. By integrating the Arrhenius equation with this model, a lifetime model based on conductor current and ambient temperature is formulated. Subsequently, considering the uncertainty in the failure time, a Weibull distribution-based reliability model is further established to achieve lifetime prediction under variable operating conditions. Finally, the preventive maintenance strategy model is developed based on the established reliability model. The red-billed blue magpie optimizer (RBMO) is utilized to determine the optimal solution for preventive maintenance threshold and the lifetime prediction cycle. Research demonstrates that optimizing the preventive maintenance strategy can significantly reduce the average cost rate (ACR), thereby minimizing the expected maintenance costs per unit of time.