Detecting Faults

Modern underground power cables are sophisticated assemblies of insulators, conductors and protective materials. Within these components are temperature sensors, which enable cable operators to monitor conditions along the cable in real time.

An optical fibre is built into a protective metal wire and that metal wire is then incorporated into the normal "screening" of the cable - the outer winding of copper wires that prevents electric fields from being transmitted outside of the cable.

Optical fibres are extremely sensitive to temperature and measurable changes to the light transmitted are used to detect the temperature along the light path. Modern sensing techniques mean that the temperature along the fibre can be measured with a resolution of around a metre. Therefore, any factor that increases the cable temperature can be rapidly detected, including human disturbance, changes in the soil around the cable, damage to cable insulation, etc.