Abstract: The problems of existing fire-fighting systems were clarified based on the analysis on the fire causes and high- risk area of large converter transformer, the influencing factors and development process of large transformer explosion and fire, as well as the characteristics of explosion and fire accidents of transformer high voltage (HV) bushing. A new fixed fire extinguishing system was also proposed. The results showed that HV bushing is a high fire risk area of large oil immersed transformer. The tank will explode when the energy of internal fault of transformer reaches a certain value. Whether a fire can be caused after a transformer explosion is closely related to whether the mixed gas leaked to the air reaches the explosion limit and whether there is enough ignition energy. The principle is that fire extinguishing based on fixed fire extinguishing system should be adhered to. It is recommended to use the new compressed air foamsprinkler system without sprinkler head and branch pipe.

Key words: large converter transformer, bushing explosion, fire;fire extinguishing system