Study Of Temperature On-Line Monitoring Techniche For High-Voltage Distributin Equipments Based On Optical Fiber Grating

In modern industry, failure and break down of electrical equipments usually show abnormal temperature. High voltage switch cabinet, electric cable and busbar in power distribution room are all important electrical equipments. In the long time of processing, contacts of electric cable,busbar and junctions between rest contact and movable contact of switch cabinet cause accidents which results in a lot of damage and loss of life and property because of high temperature. But traditional methods of temperature measurement fall behind and the function is so single that can't meet the need of real-time monitoring of the high voltage electrical equipment's temperature.The fiber grating sensor is the best choice for temperature monitoring of high voltage distribution equipments.This research includes:Firstly, the basic theory of fiber grating properties is expatiated, spectral characteristics of uniform-period fiber Bragg grating and the sensing principle of FBG under temperature and strain using the coupled-mode theory are analyzed. Steel capillary package method of fiber Bragg grating is studied.Secondly, wavelength demodulation technologies of FBG are introduced. In view of dense and messy lines in the high voltage power distribution room, a wavelength-division multiplexing plus time-division multiplexing demodulation method is designed. The demodulation system, including the photoelectric conversion and amplifier circuit, FIR filter, and FFP-TF scanning voltage generator can monitor the temperature of more than one root of a large number of cable joints. The feasibility of the system is approved by simulation and experiment.On this foundation, this paper detects peaks of the theoretical and experimental reflective spectrums using general polynomial fitting algorithm and Gaussian fitting algorithm. Gaussian fitting algorithm is proved to be the best by simulation and experiment.Experiment on temperature characteristic of FBG is carried on and general polynomial fitting algorithm is applied to the result. And the cubic polynomial fitting algorithm is proved to enhance the precision of the modulation system effectively. At last, temperature measure experiment of 24 hours is carried on.