New design of optical fibre unit (OFU) for incorporation in power cables for distributed temperature sensing (DTS) and on line monitoring

The use of distributed temperature sensing (DTS) for monitoring capability and confirming the reliable operation of power cables, is now an accepted practice using well established equipment. Whilst most utilities now insist that all new HV and EHV circuits must have optical fibre cables for DTS monitoring, there has been divided opinion as to whether the DTS optical fibre cables should be incorporated within the cable as a separate cable or tube usually within the copper wire screens, or attached to the power cables. Analysis of data on cable circuits clearly shows that the former is more desirable for most applications and essential in some cases e.g. for cables in tunnels. This paper describes a new design of optical fibre unit, which can be more easily installed within a single core cable and jointed in service. The OFU is specially designed based on practical experience over the past 10 years and is much less easily damaged during manufacture of the cable, during installation or during jointing of the cable. It is expected that this development will increase the use of fibre incorporated with power cables and lead to greater use of DTS systems.