Fault Analysis of Transformer High-Voltage Outlet Device Considering Fiber Particle Aggregation

The main insulation for high-voltage outlet devices in transformers consists of a complex arrangement of alternating multilayer oil channels and insulating pressboard, with the insulation margin approaching the design limit. As transformer voltage levels increase, high-voltage outlets are prone to sudden, unexplained discharge failures. Investigation of the causes of insulation margin reduction and the mechanisms behind these sudden failures is urgently needed to ensure the safe operation of transformers. In this study, a simulation model of a transformer outlet device was developed to analyze electric field distribution characteristics under operational conditions. The analysis revealed that the first oil gap in the stepped region of the oil-paper insulation is the weakest link in the insulation system. On the basis of the principle of equivalent electric field strength, a test oil cup was designed to explore the impact of cellulose particles on the electrical performance of insulating oil. The results indicate that under prolonged exposure to operational electric field strengths, cellulose particles aggregate, leading to a significant deterioration in the electrical performance of insulating oil. This study provides valuable insights into the correlation between particle aggregation and the reduction in safety margins of high-voltage outlet devices. These findings offer new theoretical support for tracing the causes of discharge failures in transformers.