Pyrolysis and temperature characteristics of the gas produced by power-frequency arc in transformer oil

• Published in: Case studies in thermal engineering Vol. 61; p. 104913
• Main Authors: Jia, Yunfei, Luo, Xun, Ji, Shengchang, Gao, Wanjing, Li, Simeng, Zhang, Fan
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2024; Elsevier
• Subjects: Gas composition; Gas volume; Power-frequency arc in oil; Pyrolysis; Temperature; Transformer oil; Gas composition; Pyrolysis; Temperature; Gas volume; Transformer oil; Power-frequency arc in oil
• ISSN: 2214-157X; 2214-157X
• DOI: 10.1016/j.csite.2024.104913

Oil-immersed transformers are widely used in power systems. When an arc fault occurs inside a transformer, the surrounding oil is rapidly pyrolyzed. These high-temperature, flammable gases are compressed into a high-pressure bubble, which is likely to cause tank deformations, explosions, and fires. Currently, related simulations on tank internal pressure and transformer fires are based on a constant gas composition, a constant gas production rate of 0.1 L/kJ, and a constant bubble temperature of 2000 K. This paper deals with a case of a power-frequency arc (5 kA, 30 mm, 80 ms) in transformer oil. The time-varying characteristics of pyrolyzed gas production, composition, and temperature are experimentally investigated. The percentage of hydrogen changes considerably, decreasing from 85.2 % to 70 %. The overall gas production rate increases slowly from 0.0574 L/kJ in the first 2.5 ms to 0.0982 L/kJ in 80 ms. The local temperature inside the main bubble (30 mm from the arc) decreases gradually from 2200 K to 1400 K, while the average bubble temperature decreases from 2550 K to 550 K. This case and these results provide an experimental basis for the parameter selections in the simulations about transformer internal pressure and fire progression.