Vibration Analysis And Experiment Investigation Of Large Power Transformer

As one of the important equipment in the power system,large-scale power transformers directly affect the safe and stable operation of the power grid.There are correlation characteristics between the vibration state and the fault state of the transformer.At present,the research on the transformer vibration characteristics is limited by the test method and the sample capacity,and the research results are few and their reliability remains to be verified.Based on the analysis of the vibration mechanism of the transformer,this thesis carries out the experiment research on the vibration characteristics of the transformer and the short circuit cumulative effect of the transformer vibration.It lays a good foundation for the transformer fault diagnosis based on the vibration analysis method.(1)The thesis introduces the background and significance of the subject,summarizes the detection methods of windings and cores in transformers as well as the research status of transformer vibration analysis at home and abroad,and points out its main research contents.(2)This thesis discusses the cause of the vibration of the transformer and its propagation path,analyzes the vibration mechanism of the winding and the iron core that causes the vibration of the box,and summarizes the general laws of the axial vibration of the winding.The on-site vibration tests are carried out on several 500 kV transformers that are operating online.Through analysis of vibration signals,the vibration characteristics of transformers of different types and operating years are preliminarily grasped along with the relationship between vibration and load,temperature as well as other operating parameters.(3)The analysis of test data shows that the operation of the cooling device will produce low-frequency interference such that the vibration limit of the transformer tank wall can’t meet the requirements of the current technical specifications.Based on the mechanism analysis,two methods for suppressing low-frequency interference signals are proposed to avoid the incorrect alarms of transformers.(4)A set of optical fiber sensor-based winding vibration detection system for oilimmersed power transformers is developed.It is able to directly measure the vibration of transformer windings in a high voltage,strong electromagnetic field,full insulating oil,and accurately determine the mechanical state and its changing trends of the transformer windings.(5)A short-circuit impulse cumulative effect test is performed on 110 kV and 220 kV oil-immersed power transformers to investigate the changes in the vibration characteristics of the transformer during both no-load and load operation in multiple short-circuit faults.Test results verify the gradual deterioration process in internal mechanical state of the transformer.