Research On On-line Monitoring System Of Power Cable Temperature Based On Fiber Bragg Grating

With the continuous increase of the total power consumption in China,the power cable plays an increasingly important role in the urban power grid.Because the cable is in the environment of high voltage and high radiation for a long time,the temperature will be too high,sometimes resulting in insulation damage,or even fire.Therefore,the cable temperature is one of the key factors affecting the operation of cable stability,monitoring and analysis of its internal temperature is of great significance.Electrical sensors should not be used due to the bad laying environment of cables.Therefore,the fiber grating sensor with strong anti-interference,good flexibility and temperature sensitivity is used in this thesis.In order to timely measure the cable temperature and avoid accidents,an online monitoring system for power cable temperature is designed based on the fiber Bragg grating.It has been verified by experiments that this kind of temperature measurement method of power cable not only has strong anti-electromagnetic interference ability,but also has high accuracy.Therefore,fiber Bragg grating sensor is finally adopted in this experiment to measure the temperature of cable.Firstly,the research status of cable temperature on-line monitoring technology at home and abroad and the principle of fiber Bragg grating temperature measurement are introduced and analyzed in detail.Through comparing and analyzing the advantages and disadvantages of several methods of temperature measurement for cables,the temperature measurement scheme is determined in the thesis.The finite element analysis software ANSYS Workbench 18.2 is used to simulate the internal temperature field of power cable,determining the hottest point of the internal temperature.And the temperature rise equation of cable core temperature and skin temperature is obtained at different ambient temperatures through several simulation data,and the paper proved the accuracy of the formula.In practical application,the fiber Bragg grating is laid on the outside of the cable,the temperature of the cable skin is measured,and then the temperature of the cable core can be calculated through the temperature rise equation,so as to achieve the purpose of monitoring the temperature rise of the cable.The method is simple to lay and easy to operate.At the same time,the paper analyzed the factors affecting the temperature of direct buried cable(ambient temperature,buried depth,thermal conductivity),and obtained the relation between temperature,thermal conductivity and ambient temperature of three-core cable in the fixed buried depth.According to the theoretical analysis,completing the hardware construction of the cable temperature monitoring system,and explaining the working principle of optical devices(light source,ring,fiber grating,etc.)and fiber Bragg demodulation module(FBGA).In order to communicate between FBGA and PC,the upper computer software is written by calling DLL dynamic link library in LABVIEW development environment,which can realize the function of accurately displaying temperature value,center wavelength value and waveform on the interface.Finally,the software and hardware systems were connected,the temperature measuring platform was built,the grating was placed in the heating device,and the calibration experiment was completed between 20? and 100?,proving the direct proportional relationship between the temperature and the center wavelength.And the feasibility of the system was proved by error analysis experiment.