Analysis of Uneven Insulation Deterioration of 110 kV Transformer Bushing by Moisture

This paper presents a comprehensive study on the moisture characteristics of oil-paper insulated transformer bushings using frequency domain dielectric spectroscopy. The dielectric response properties of oil-paper insulation models subjected to uniform and non-uniform moisture conditions are analyzed based on the principles of frequency domain spectroscopy. Furthermore, research efforts are carried out to investigate the diagnosis and practical application of field oil-paper insulated bushings using dielectric spectroscopy tests. A novel assessment method is proposed to evaluate the moisture uniformity in oil-paper insulation equipment, considering the distinct dielectric response characteristics associated with uniform and non-uniform moisture distribution. Specifically, non-uniform moisture distribution leads to prominent loss peaks and fluctuations in the curves. The proposed theoretical model is validated through frequency domain dielectric spectroscopy tests and physical and chemical analysis of disintegrated transformer bushings. The study provides a reliable approach for on-site moisture assessment of transformer bushings, thereby enhancing the accuracy of insulation health diagnosis in the presence of non-uniform moisture conditions.