Decline Analysis and Quantitative Characterization of the Strap Contacts of the Valve-Side Bushing of the UHV Converter Transformer

The valve-side bushing of the UHV converter transformer is important insulating equipment in the DC transmission project and the strap contacts inside the bushing. As the electrical connection part at the copper-aluminum intersection, strap contacts are also the most heat-emitting part, which directly affects the safety of the entire bushing operation. The running conditions of strap contacts are complex, such as high current, mechanical vibration, insulating oil leakage, wear, deformation, etc. All these factors affect the decay and failure of the running condition of the contacts. To address the problems of unknown deterioration mechanisms and difficult extraction of internal defects, this paper analyzes the causes of overheating defects and proposes the extraction and quantitative characterization of decline features based on the analysis of test data. Firstly, the surface characteristics of the degraded strap contacts are analyzed, and the temperature rise characteristics after degradation are investigated. Then, the degradation characteristics of the contact finger under the influence of temperature rise are analyzed, and the degradation feature set is established. Finally, the degradation feature set of the contact finger is processed by the kernel principal component analysis algorithm, and the feature values with a contribution rate of more than 95% in the feature set are used as the degradation feature vector. Through the example demonstration analysis, the deterioration mechanism of the strap contacts are further demonstrated, which is important for its structure optimization and condition monitoring.