Research Of Transformer Insulation Condition Diagnosis Method Based On Relaxation Process

The transformer is the key equipment in electric power system, whosesafe operation is of great significance to the reliability of electric powersystem and the operation life of the transformer largely depends on itsinsulation condition. The insulation structure of oil-immersed transformer,which is widely used in electric power system, is oil-paper insulationsystem. Thus, condition assessment of complicated transformer could beextended by the condition research of simplified oil-paper insulation. It istherefore of great engineering values and academic significance to studythe condition assessment of oil-paper insulation and provide proof for lifemanagement of transformer by assess insulation condition of transformeraccording this method.In recent years, one of the research highlights is the non-destructiveinsulation assessment method based on the information that relaxationprocess carries. The present paper first studied the information reflected byrelaxation current of oil-paper insulation in time domain, especially therelationship between the relaxation current and moisture in paper. Thenaccelerated aging test was done. According to the results, thetransformation law of the relaxation current in time domain was obtained.The relationship between the relaxation current and by-products ofoil-paper insulation was also obtained. The relaxation model in timedomain was built at last. Then an attempt to correlate the relaxation currentin time domain and dielectric spectrum in frequency domain was realized.Based on the above laboratory tests, condition assessment of transformerinsulation based on the relaxation current measurement was discussed. The present thesis conducts in-depth research into direct correlationbetween relaxation current of oil-paper insulation in time domain and thephysical and chemical structure of oil-paper, providing theoretical basis forcondition assessment of transformer insulation.