Investigation on gas generation characteristics in transformer oil under vibration.

Operating experience has shown that characteristic gases can be found in oil‐immersed power transformers and high‐voltage reactors under strong vibration without discharge or thermal faults occurring. This will cause misdiagnosis of Dissolved Gases Analysis (DGA). In this study, generation characteristics and mechanism of characteristic gases in transformer oil dependent on vibration are investigated. The results show that there is a vibration pressure threshold that makes characteristic gases such as hydrogen (H2), methane (CH4), ethylene (C2H4), ethane (C2H6), and acetylene (C2H2) appear in transformer oil. The concentration of each characteristic gas increases with the increase of vibration pressure. Furthermore, misdiagnosis of insulation status which may be caused by vibration is illustrated based on Duval triangles method. Besides, vibration bubbling phenomenon in the experiment is observed. The generation mechanism of characteristic gases is analyzed with bubble dynamics under vibration. Higher vibration pressure induces cavitation processes and creates local thermal effects, which is the main reason for the generation of characteristic gases. A method based on combination of Duval triangle 1 and assistant triangle is proposed to distinguish characteristic gases generated by vibration from those generated by discharge and thermal faults. The results may provide theoretical support for fault identification and insulation state assessment of oil‐immersed power transformers and high‐voltage reactors. [ABSTRACT FROM AUTHOR]