Research On Analysis Of The Micro Water Content Of Oil-Paper Insulation Transformer Based On Equivalent Circuit Method

This study comes from the national natural fund project Method Based on Circuit Analysis Response and Recovery Voltage Insulation Aging Diagnosis(NO.61174117). The reliability of the operation of oiled paper insulation transformer is very important to the safe and stable operation of power system, the deterioration of insulation performance is the main causes of transformer failure, and the presence of water directly influences of transformer insulation. Therefore, it is to economy and meaningful to take appropriate measures to evaluate of micro water content in oil paper insulation transformer effectively. The paper takes the moisture of oil-paper transformer as the research object, bases on a large number of field return voltage test of transformer oil-paper insulation, by establishing relaxation response equivalent circuit of oil-paper insulation, deeply analyze the parameter of relaxation response equivalent circuit and excavates the change rule between the micro water content and equivalent circuit characteristic, then inquires into the effective diagnosis method for the micro water content of insulation condition transformer.Main contributions of this thesis are listed as following:(1)This paper analyzes the basic structure and the polarization characteristics of water molecules and their influence on transformer insulation in theory, and research many kinds of evaluation method of micro water content in oil paper insulation transformer. Based on that, the theory of return voltage method based on dielectric response is put forward to assess the micro water content of oil-paper insulation transformer.(2)This paper establishes relaxation response equivalent circuit of oil-paper insulation transformer and shift the parameter differentiate problems into function optimization problems by using appropriate objective function. Also, it adopts the Particle Swarm Optimization(PSO)with compression factor to solve the objective function and derives the equation of return voltage, compares the calculated values with measured values of return voltage polarization to prove the validity of the circuit model and mathematical model.(3)According to different relaxation time to group and discuss the relationship between the equivalent circuit, polarization resistance, insulation resistance, capacitance, geometric capacitance and the micro water content of oil-paper insulation transformer, and comes up with the method of diagnosing the micro water content of oil-paper insulation transformer based on relaxation response equivalent circuit and chooses the transformer instance to certify.(4)Analyzes the inner link between the different micro water content of oil-paper insulation transformer and return voltage polarization and systematically investigate the relationship between the characteristic of return voltage (the time constant, initial slope, maximum voltage, peak measuring response time) and the micro water content of oil-paper insulation transformer,sums up the method of assessing the the micro water content of oil-paper insulation transformer by applying the characteristic of return voltage.(5)Sets up oil-paper insulation transformer models with different water content in laboratory and test the return voltage. By comparing the data of transformer models and the data of field test to further certify the method of assessing the the micro water content of oil-paper insulation transformer by applying the characteristic of return voltage.