Spread Spectrum Techniques for Measurement of Dielectric Aging on Low Voltage Cables for Nuclear Power Plants

Spread spectrum time domain reflectometry (SSTDR) is used to test dielectric aging of a cable type used in the nuclear power plant industry. A 16 AWG twisted pair shielded cable is thermally aged to the equivalence of 50 years in service, and SSTDR data are collected at 10-year intervals during the aging process. The SSTDR data shows that velocity of propagation and characteristic impedance decrease as the cable ages (increasing the electrical permittivity), making them suitable markers for monitoring aging and demonstrating the ability of SSTDR to determine this aging.