How to Apply Distributed Optical Fiber Temperature System to Measure the Temperature of Cable

Abstract: In order to discuss the prospect of distributed optical fiber temperature system applied in HV cable temperature on-line monitoring, the paper presents basic principles and characteristics of this system. The precision of temperature measurement, location, response time and reliability are examined through two-month field test. Test results show that the system has many advantages, including small error in temperature and location measurement, short response time, reliable operation and measuring the temperature in long distance and large area. The technology can be very effective in on-line monitoring of cable temperature and provide direct data for calculating cable ampacity. What is more, it can keep the fire away from fire. 

Key words:  distributed optical fiber temperature system, cable temperature, cable insulation, on-line monitoring, ampacity     

Introduction

The average failure rate of Chinese grid cables is higher than that of some developed countries. One vital reason for higher rate is a lack of efficient on-line monitoring while temperature on-line monitoring is one of the most important aspects. It is necessary to perform accurate and real-time temperature monitoring for installed cables and the environment to determine best and safest cable ampacity. Such accidents can be avoid if early warning is delivered through temperature measurement at the early stage of the accident and then countermeasures are taken at once. The traditional method of measuring the temperature is to install thermal detectors such as thermocouple at the important position of cable to measure the temperature. This method can only measure the temperature of part of cable system not the whole cable. However, one or several optical fibers can monitor line-type equipment or point-type equipment which covers miles of ground via the distributed optical fiber temperature measurement system. The technology is used to conduct two-month on-site test for one 220kV electric cable installed in a UHV cable experiment room.