Discharge Stage Divison of Oil-pressboard Insulation based on the Amplitude Variation of Electrical-Magnetic-Acoustic Signal

Surface discharge is one of the most serious types of discharge faults in transformer oil-paper insulation structures. In order to accurately obtain the changes in characteristic parameters during the development process of surface discharge of oil-paper insulation under AC voltage, a simulation experimental platform for the development process of surface discharge was built and a measurement system which can meet the synchronous online monitoring requirements of electrical, magnetic, and acoustic physical quantities during the discharge development process was established in this paper. On this basis, typical features of multiple physical parameters during the development of surface discharge were extracted, and the discharge process can be divided into stages by analyzing the amplitude changes of the feature parameters throughout the entire process. The corresponding stage features and mechanism overview were provided. The experimental results indicate that by means of analyzing the typical characteristics and variation patterns of multiple parameters, the development process of surface discharge can be divided into four stages: initial dis-charge stage, low energy discharge development stage, high energy discharge intense stage, and near breakdown stage. The stage characteristics are related to charge distribution and insulation material resistance strength. Compared to conventional single parameter monitoring methods, the multi parameter synchronous detection method will provide a more reliable and accurate reference evidence for transformer surface discharge fault diagnosis and timely warning.