Apparatus for and method of monitoring the corrosion in electrical power cables by measuring the variation in induced eddy currents

摘要

A metal cable corrosion monitor comprises a sensing head (14) located about a multi strand cable (1). The sensing head includes a field windings (3) for applying a magnetic field coaxially to a portion of the cable to be monitored. A pick-up coil (2) encircles the portion and detects magnetic flux parallel with the cable and linking with the area of the pick-up coil. The signals from the pick-up coil are processed by a high gain amplifier (8) and phase sensitive detectors (7) and (6), the former phase sensitive detector producing an output in phase with the field winding driving frequency and the latter phase sensitive detector producing a quadruture output relative to the field winding driving frequency. By observation of the amplitude and the phase output parameters it is possible to detect corrosion of a single or multi strand cable. A particular format of field winding is disclosed whereby the effects of induced inter strand currents can be reduced.