Investigation of Fault Locating Method for Underground Cable Lines using Optical Fiber Type Temperature Sensors

Abstract

In order to investigate a fault locating method for cable lines, we measured temperature rise at the shield near each fault point by artifical fault tests. We also examined the methods of how to attach the optical fiber type temperature sensors. The results can be summarized as follows:
(1) When the fault curent is 400A, the shield temperature rise at the fault point can be appraised by the mean value during 30 seconds after the fault initiation. The temperature rise value are several tens degrees. Therefore, we considered that there was a good possibility of locating the fault point at a moment by optical fiber type temperature sensors.
(2) Methods of attaching optical fiber type temperature sensors to a cable can be proposed as follows.
•In case that the shields are soft-copper wires, optical fiber type temperature sensors are necessary in axisymmetrically located two lines, and are inserted in the gap between soft-copper wires at a winding pitch of 27cm.
•In case that the shields are soft-copper tapes, optical fiber type temperature sensors are necessary also in axisymmetrically located two lines, and are wound around the soft-copper tapes at a winding pitch of 40cm.