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In the light of tests showing that the fire resistance of transformers containing liquid dielectrics depends on the overall transformer design as well as on the properties of the liquid, a procedure is described for dealing with the standards' failure to allow for the design aspect. The EdF specification for dry transformer component and overall testing is outlined, and a parallel procedure for liquid-filled transformers is set out covering the risk of toxic combustion products, an index of fire resistance time, and a more detailed definition of safety level. Four reasons are given for considering the transformer as a potential seat of fires as well as a victim of conflagration of external origin. The liquid-insulated power transformer is seen as a considerably cheaper alternative to a dry one of comparable size and performance in dusty, damp and corrosive environments.