Fire and Explosion Risks and Consequences in Electrical Substations—A Transformer Case Study

Abstract

This study aims to find how fires and explosions can occur in enclosed spaces where electrical transformers are installed and to investigate the consequences of the damages to the surrounding areas caused by these accidents. This study began with the collection of a mineral oil waste sample from an indoor substation transformer in Riyadh, Saudi Arabia. This sample was analyzed to determine its composition. Results revealed that 30 components ranging from C6 to C30 were detected in the sample. The mixture flammability limits, calculated using Le Chatelier rules and found to be 0.97 and 6.56, indicated that the vapor mixture for the waste oil sample was not flammable at 25 °C and 1 atm. Consequence analysis was used to predict the outcome of fire and explosion events based on a transformer with a capacity of 1100 liters. The peak overpressure generated by an explosion was estimated to be 80.97 kPa. Moreover, the thermal radiation produced by various types of fires was estimated as a function of the distance from the accident center. The thermal flux from a boiling liquid expanding vapor explosion (BLEVE) was 99.8 kW/m2, which is greater than that from jet and pool fires. The probability of an individual suffering injury or dying as a result of exposure to fire and/or an explosion was estimated using dose-response models. The results showed that the peak overpressure produced by an explosion can cause severe damage within 20 m of the explosion center. However, the results also showed that there is a 100% probability of the thermal radiation from a BLEVE causing fatalities up to a distance of 140 m. The risk due to the fragmentation of the transformer tanks was also assessed, and a majority of fragments would land within a range of 111.2 m.