Corrosion assessment of electrical contact elements in the valve-side ascending flange of UHV converter transformer based on LIBS technology

The valve-side ascending flange of converter transformer is a critical area where valve-side winding lead-out wires are connected to the current-carrying bushing. The electrical contact elements within it carry high voltage and large currents, making them susceptible to corrosion and ageing, which poses a threat to the safe operation of the ultra-high voltage transmission system. In this study, laser-induced breakdown spectroscopy combined with the deep neural network algorithm was used to assess and analyze the corrosion of the contact strips. Initially, the disassembled louvers with varying corrosion degree were characterized and analyzed using scanning electron microscope, energy dispersive spectrometer, and X-ray diffractometer, corrosion experiments were conducted to verify the corrosion process of the contact strips, and a corrosion grading standard of the louvers was developed based on the test results of contact resistance and relevant standards. The louver samples representing four corrosion grades were tested, and the obtained spectral data underwent meticulous preprocessing using various methods. Combining principal component analysis and the DNN algorithm, the LIBS corrosion grading model was established, achieving an exceptional recognition accuracy of 95%. The results demonstrate the tremendous potential of LIBS technology in the corrosion assessment and analysis of electrical contact elements.