Highly sensitive location method of an abnormal temperature point in a cable by frequency domain reflectometry

This paper demonstrates that it is possible to locate very precisely a point showing a high temperature in a polymer insulated cable. A coaxial communication cable with a length of 32 m insulated by low density polyethylene or a flat inhouse electric cord with a length of 21 m insulated by polyvinyl chloride was heated at different positions for different lengths. The ratio between the incident and reflected powers of electromagnetic waves was measured using a network analyzer in a wide frequency range and the obtained spectra were analyzed by inverse Fourier transform. As a result, the position exhibiting a temperature higher than the adjacent points can be located with a spatial resolution as short as 2.5 cm.