Experimental study on the autoignition characteristics of pure and oil-impregnated transformer insulating paper board

Abstract

In order to deepen the knowledge of transformer fire dynamics and its fire prevention, an experimental study on autoignition and combustion characteristics of pure insulating transformer paper board (PIPB) and oil-impregnated transformer insulating paper board (OIIPB) were performed. Ignition time, heat release rate (HRR), O2, CO and CO2 concentrations were obtained by a cone calorimeter under different external radiant heat fluxes. The results show that two peaks of HRR occurred during the burning process of PIPB, where three peaks occurred for the OIIPB. The first peak of the OIIPB occurred earlier than that of PIPB, which indicates that OIIPB is more ignitable, but the maximum HRR of PIPB is higher than that of OIIPB, which indicates that the combustion intensity of PIPB is larger. The PIPB has a relatively higher CO and CO2 yield and O2 consumption. The results demonstrate that both the tested 3-mm-thick PIPB and OIIPB samples in this study can be considered as thermally thick materials. Autoignition time of OIIPB and PIPB under external heat fluxes could be predicted based an empirical model, and the critical heat fluxes were obtained based on the models and the ignition data.