Experimental investigation on the suppression characteristics of new natural ester soybean oil transformer fire in room

In this paper, an experimental test was conducted to assess the effectiveness of different fire extinguishing systems on a new natural ester soybean oil transformer fire. The fire extinguishing characteristics, extinguishing times, fire plume temperatures, oil temperatures in the transformer, and the total heat flux intensity of the fire field were observed. It was found that a fine water mist extinguished the soybean oil transformer fire without re-burning, while foam spray extinguished the fire with a violent re-burning. The overall extinguishing time of fine water mist was significantly shorter than that of foam spray. After the implementation of water mist, the fire plume centerline temperature dropped to 77.3℃, smaller than that with foam spray of 95.6℃. The temperature rebounded to 207°C when the fine water mist was applied, 24% lower than that of the foam spray. When foam spray was applied, the maximum transformer internal oil temperature was 300.8℃, similar to that achieved with the water mist system of 303.2℃. However, the temperature decay rate during the rapid cooling stage was only 42% of that observed with the water mist fire extinguishing method. Due to the re-burning, the rebound duration of the total heat flux intensity was significantly greater in foam spray fire extinguishing. Under the current conditions, the extinguishing effectiveness of fine water mist was superior to that of foam spray. The results of this study can provide the valuable insights for the choice of fire extinguishing system of the new natural ester oil-immersed transformer.