Characteristics impedance modeling for shielding damage of I&C cables in NPPs using TFDR

To enhance the precision and efficacy in detecting defects of instrumentation and control (I&C) cables within nuclear power plants, this study proposes a model. This model, used in tandem with the time–frequency domain reflectometry method, creates a quantitative association between the severities of a defect and its time–frequency properties. To verify correctness, the proposed model was established on transmission lines to concentrate on their time–frequency response utilizing MATLAB. Besides, the experiment was conducted on multi-core I&C cables with varying severities of external shielding damage. The results indicate that tiny damage to the shielding marginally modifies the characteristic impedance, rendering time-domain reflection signals almost undetectable to the human eye. However, the time–frequency analysis effectively highlights the signature of defects. From the experimental results, the experimental outcomes support the simulation results, confirming the reliability of proposed model. This technique demonstrates superior sensitivity and accuracy in identifying such defects, suggesting that the severity of external shielding damage correlates directly with the peak magnitude in the time–frequency domain cross-correlation. This method augments the capacity to extract detailed defect information during cable maintenance, aiding in the formulation of more comprehensive maintenance strategies.