Patent ID: 7966137

Claim:
A method for monitoring a condition of an electrical cable, said method comprising the steps of: calculating, using an LIRA analyzer, a complex cable impedance Z DUT as a function of a frequency f specified by an amplitude and a phase, wherein the frequency f is a frequency of a multifrequency signal wave applied to the cable by a modulator, and wherein the multifrequency signal wave is phase and amplitude modulated by a cable impedance; translating the calculated complex cable impedance into a time domain t′; calculating a frequency f′ in the time domain t′, wherein the frequency f′ is the fundamental frequency of a pseudo-periodic function of radial frequency ω′ and amplitude A in the time domain t′ due to wave reflection of the multifrequency signal wave at a distance d from an end of the cable, and wherein the frequency f′ is calculated by applying: f ′ = ω ′ 2 ⁢ π = 2 ⁢ d v r ⁢ v 0 in which v 0 is the speed of light in a vacuum and v r is an estimated relative phase velocity of an electrical signal in the cable; performing a power spectrum analysis of both amplitude and phase of the complex cable impedance in the time domain t′ to find and localize any local degradation to insulation of the cable; identifying frequency components f′ 1 , f″ 2 , f″ n , in the power spectrum of the time domain t′ due to wave reflections of the multifrequency signal wave at locations x 1 , x 2 , . . . , x n along the cable, the wave reflections being due to discontinuities in electrical parameters of the cable; and calculating each of the locations x i by applying: x i = v r ⁢ v 0 ⁢ f i ″ 2 .