The Study Of Cable Connector's Temperature Monitoring System Using Distributed Fiber Bragg Grating

With the boosting automation and the increasing load, more and more cables have been used in the large-scale metallurgy, chemical industry, power plants, substations, and other enterprises. Cable connector is overheating as a result of large contact resistance or aging problem. There is a potential of fire if the temperature of these important hot spots can not be monitored in real-time. As a result, it may damage the transformer, causing the line paralysis and the power failure all of a sudden, consequently, bring incalculable economic losses to the society and industrial production.The joint of high voltage power lines, which are over 6 kV, account for the main proportion of overheating ones. The conventional temperature sensors can not meet the security needs due to the higher voltage. Moreover, the traditional fiber-optic temperature measurement system has a shortcoming of longer scaning time. Hence, FBG(Fiber Bragg Grating) temperature monitoring system is the best choice for monitoring the failure of high-voltage cable joints.The primary research of this paper includes:Firstly, the basic theory of FBG is analyzed. The spectrum of uniform-period FBG is analyzed by the coupling-mode theory together with FBG sensing theory for strain and temperature is analyzed. In addition, FBG sensor′s steel capillary packaging technique and sensing properties is studied.Secondly, the demodulation technology of distributed FBG sensor is studied in this paper. Taking into consideration of the merits and demerits of various demodulation methods, a wavelength division multiplexing plus time-division multiplexing demodulation system for dense and messy cable channel is designed. The cable joint monitoring system, which uses the demodulation system, can monitor the temperature of more than one root of a number of cable joints. Finally, a signal processing system for FBG sensor is designed. In this system, the core FPGA chip is XCS250E. The system includes: photoelectric conversion and amplifier circuit, high-performanced FIR filter, and FFP-TF scanning voltage generator. The feasibility of the system is approved by simulation and experiment. Moreover, being capable of communicating with PC through RS-232 interface, sensor network, thereby, can be composed.