Location attempts of a heated and irradiated portion in a silicone rubber insulated cable by frequency domain reflectometry and line resonance analysis

Electric cables play important roles for supplying power and for transmitting information and control signals. Therefore, their degradation may cause a serious problem. Silicone rubber (SiR) is widely used for electrical insulation in safety-related cables in nuclear power plants. In this paper, the ability of locating a degraded portion in a duplex cable insulated with SiR was compared between a system based on frequency domain reflectometry (FDR) being developed by the authors and a commercially available system called line resonance analysis (LIRA). Reflecting the fact that the FDR system can expand the measurement frequency range, FDR shows a higher sensitivity and a better resolution than LIRA. However, both methods cannot detect the degradation of SiR before its further use becomes uncommendable.