Study On Core Loss Characteristics Of Oil - Immersed Transformer And On - Line Monitoring Of Fiber Bragg Grating

The reliability of the oil immersed transformer is largely related to the efficiency and safety of power equipment and power grid operation. Actually, more than half faults of the transformer due to overheating, which disables the insulating ability of its internal structure, and then overheating impacts the available period of the transformer. This thesis designs a system of fiber grating monitoring for oil immersed transformer iron core temperature referencing the Part 2 of GB/T1094.2 Power transformer rTemperature rise and the Part 7 of GB/T1094.7 Power transformer:the guideline of Oil-immersed power transformer load, which provides a direct and efficient method to monitor the internal temperature of oil immersed transformer.This thesis use classification algorithm to calculate iron core loss, and make a heat loss model, Using the optical fiber sensing to monitor the iron core surface temperature of the oil-immersed transformer and contrasting thermal characteristics of iron core at temperature rise test. The main contents are as follows:(1) analyzing the loss of the iron core and the elements of this loss:eddy current loss, hysteresis loss and added loss.It calculates the mathematical relationship of iron core no-load loss in the aspect of engineering referencing the law of electromagnetic induction, Closed magnetic circuit current law and Joule’s law.The iron core simulation model is set up for finite element analysis to compute the location and temperature range of core hot spot.It provides a reliable referencing for the position where sensor be installed.(2) It designs optical fiber sensors, coupler and optical fiber connector for monitoring the iron core surface temperature combined with SFZ11-10000/35 type transformer structure characteristics. The optical fiber sensing structure, principle and mathematical model are analyzed to guarantee there are none metal components and active-device when iron core surface temperature of transformer is direct detected.The influence of active sensing error and point discharge is eliminated to a great extent in strong magnetic environment. Meanwhile, the data about aging phenomena is analyzed after temperature cycle fatigue test to make sure the stability of transformer in engineering practice.(3) The reasonable monitoring scheme is formulated in combination with the ANSYS simulation results and the principle of optical fiber sensing.And the optical fiber sensing network is structured,then completing installation at last. Monitoring system is troubleshooted and tested after the oil is filled.(4) Considering the limit of temperature rise,the collected data is analyzed after 17.5-hour experiment of temperature rise. The iron core surface temperature is influenced by different experiments. These results demonstrate the features of temperature rise, which verify the validity of the simulation and illustrate that there is the likelihood about the fiber optic monitoring worked on surface temperature of oil-immersed transformer iron core can be accomplished.