Substantiating the parametric temperature mode during a fire on transformers placed inside protective structures

The object of this study was the change in temperature during a fire on transformers located in protective structures. Investigating the change in temperature during a fire on transformers located in protective structures is one of the priority tasks for protecting the economy and national security of the country. The studies solved the problem of fire resistance of the enclosing structures of protective structures in which the transformer is located. The fire resistance of enclosing structures has been confirmed by meeting the conditions related, in particular, to the calculated value of the critical temperature of the material. The selection of the calculation scenario for investigating the temperature regime during a fire on a transformer located in a protective structure was carried out according to two scenarios of the occurrence and spread of fires. The study demonstrated temperature changes in the protective structure during the burning of the transformer based on data of the temperature sensor installed at heights of 1 m, 10 m, and 18 m above the place of occurrence of combustion. Certain conditions were taken into account for the calculation scenarios of the spread of fire and changes in the temperature effect on building structures. Cases when an automatic water fire extinguishing system is functioning and not functioning in the protective structure were taken into account. In order to substantiate the temperature regime during a transformer fire, the conditions of the greatest impact of temperature on building structures were adopted. The following conditions were accepted: there is no automatic fire extinguishing system in the protective room; temperature sensor readings were located at a level of 18 m from the floor level of the protective structure. The calculation of the temperature regime during a transformer fire, which is located in the protective structure, was carried out using a field model, employing the reaction of simple stoichiometry (transformer oil can contain only carbon, hydrogen, oxygen, and nitrogen atoms). Based on the results of this study, a modified temperature regime during a fire on transformers located in protective structures was substantiated. The maximum temperature range for a developed fire was from 900 °C to 1100 °C. A standardized time (up to 30 minutes) has also been established during which the building structures of protective structures must withstand the effects of the modified temperature regime