Study on the Aging Characteristics of Retired O-Ring Seals in Transformers

Transformers are integral to the functionality of power systems. Yet, they are susceptible to the deteriorative impacts of persistent exposure to adverse environmental conditions, including moisture, elevated temperatures, mechanical stress, and salt fog, which can cause the O-ring seals within these transformers to degrade over time. The advanced aging of these seals can culminate in their failure, potentially resulting in critical safety incidents, such as the leakage of transformer oil. Nitrile rubber has become a prevalent material in transformer sealing systems, largely due to its extended service life, economic efficiency, and favorable elastic properties. Currently, artificial accelerated aging methodologies are frequently employed to examine the aging characteristics of seals; however, these methods often fail to account for the full spectrum of environmental aging factors. In contrast, the direct assessment of the performance of O-ring seals that have naturally aged over an extended period presents a more accurate approach to studying their aging characteristics. This study focuses on O-ring seals from a transformer involved in an oil leakage incident within a power grid in southern China, scrutinizing the aging characteristics of these retired nitrile rubber O-ring seals, which have been in service for a duration of 15 years. A suite of tests and characterization techniques, including hardness, mass, dimensional analysis, Fourier-transform infrared spectroscopy (FTIR), macroscopic examination, microscopic analysis, and elemental composition assessment, have been utilized to elucidate their aging properties. The findings from this research are instrumental in enhancing the materials and design of seals, thereby reducing the incidence of oil leakage incidents. This contributes significantly to the safety and stability of the power system, ensuring its reliable operation.