(59m) Possible FIRE Scenarios in Electrical Substations Due to Formation of Flammable Mixtures

This study investigates the possibility of the occurrence of fire and explosion accidents caused by the vaporization of hydrocarbon components derived from mineral oil (dielectric Fluid) which is used as transformer insulating fluid in electrical substations. Samples of mineral oil have been collected from one of the electrical substations in Riyadh, Saudi Arabia. The samples were analyzed using Gas Chromatography Mass Spectrometry (GC-MS) to identify its composition. The results obtained from the GC-MS indicated that, 33 components varying from C₈ to C₃₅ were present in the sample. Results revealed that the majority of these components are categorized as Alkane, Alkene, and Alkyne groups with some species from the Ketone, Alcohol, Aromatics, and Anhydride groups. About 25 % of the species were from Alkane group.

Mole fractions of the components presented in the liquid phase were obtained from the GC-MS results. The stoichiometric concentration method was used to calculate the Lower Flammability Limits (LFL) and the Upper Flammability Limits (UFL) for each component. The LFL and UFL for the mixture (LFL_mix and UFL_mix) were calculated in accordance to Le Chatelier equation. The LFL_mix and UFL_mix were found to be 0.88 vol. % and 5.75 vol. %. Then flammability diagram was used to determine if a flammable mixture existed. Results indicate that the vapour mixture for the sample is not flammable at 25^oC and 1 atm. However, the vapour mixture was found to be flammable at 500^oC.