Effects of ignition energy, oil volume and ignition position on transformer oil explosions

The transformer oil is easy to explode in enclosed power equipment. However, the explosion characteristics of transformer oil have not been clearly clarified in previous studies. In this paper, the effects of ignition energy, oil volume, and ignition position on the overpressure buildup and fireball behavior caused by transformer oil explosions are investigated. Experimental results show that four typical stages of cloud occlusion, rapid development, combustion stage and free diffusion can be found during the fireball evolution. The fireball shape is significantly affected by the ignition position. With the increase of oil volume, both the maximum fireball radius and the maximum fireball area gradually increase. The double-peak overpressure structure is first observed and the first peak overpressure is always larger than the second one. The first overpressure peak is generated by the explosive explosion while the second overpressure peak is induced by the coupling between the combustion waves of initial fireballs and the reflected waves of shock waves induced by the explosive. With the increase of oil volume, the maximum overpressure decreases due to the energy absorption. The maximum overpressure for center ignition is larger than that for bottom ignition or top ignition.