Locating fault in metal screened twisted pair multicore electrical communication cables, by injecting pulse of set amplitude, shape and duration into cable and analyzing pulse reflections

摘要

An electrical pulse of given shape, amplitude and duration is injected at a first cable (5a) end between metallic screen (51a) and one of the internal conductors (55b,55c,55d), so as to propagate an electromagnetic wave along the screen. The electrical signals appearing at the first cable end are analyzed over a set time period, so a to detect the presence of echoes corresponding to the reflections of the electromagnetic wave from the fault (54). The fault causes local alterations to the cables electrical parameters due to deterioration in the external sheath (50) and/or the metal screen (51a). The distance from the first cable end to the fault is determined from, the time necessary for the electromagnetic wave to travel to and be reflected from the fault and the speed of propagation in the cable.