A Power-Cable Temperature Monitoring System

A novel device capable of monitoring the sheath temperature of underground power cables and indicating isolated hot spots is described. The novelty is in the hot-spot detecting principle, which is based on the use of a thin liquid-filled coaxial sensing cable attached to the power cable. A hot spot causes the liquid within the sensing cable to boil, forming a vapour bubble, the latter being detected by means of a pulse-echo radar method. Design features of the device and a trial installation are described, indicating the maximum operating range to be 1400 feet and the nominal response temperature 75°C.