Jiaqing Zhang

Effects of external radiation heat flux on combustion characteristics of pure and oil-impregnated transformer insulating paperboard

The effects of external radiation heat flux on the combustion characteristics of pure transformer insulating paperboard (PTIP) and oil‐impregnated transformer insulating paperboard (OITIP) were investigated experimentally. The experiments were conducted with the cone calorimeter using five external radiation heat fluxes that ranged from 25 to 80 kW/m2. The results showed that the ignition time decreased with the external radiation heat flux, and the ignition time of PTIP was much longer than that of OITIP. Both the PTIP and OITIP are thermal thick materials, and the critical radiation heat flux of the PTIP was larger than that of the OITIP. For the PTIP, the peak of the heat release rate (HRR) and toxic gas productions had no significant difference, while those of the OITIP increased with the external radiation heat flux. The HRR peak of the PTIP was larger than that of the OITIP with the external radiation heat fluxes of 25, 35, 50, and 65 kW/m2. When the radiation heat flux increased to 80 kW/m2, the HRR peak of the OITIP became higher. From the perspective of the CO production rate, the hazard of PTIP fires was more severe than that of OITIP fires under the external radiation heat fluxes of 25 and 35 kW/m2. The CO production rate of the PITP was lower than that of the OITP with the high external radiation heat fluxes of 50, 65 and 80 kW/m2.

Smoke Filling in a Confined Compartment with Single Ceiling Vent

A simple analytical model which is suitable to determine the smoke filling time in a confined compartment with single ceiling vent is presented in this paper. In addition to the theoretical analysis, an experimental study is conducted to evaluate the feasibility of the application of the model. The experimental results show that smoke filling time varies with different dimensions of the ceiling vent when the dimension of fire source is relatively small (the diameter of fire source is 0.1 m). However, in the case of a high heat release rate of fire source (the diameter of fire source is no smaller than 0.14 m), the effect of the dimension of the ceiling vent on smoke filling time could be approximately ignored. Zukoski’s ceiling exit model can be used to predict the smoke filling process in confined compartment with single ceiling vent.

On Data Analysis in Forest Fire Induced Breakdown of the Transmission Line

The forest fire is one of the great threats to the operation of transmission line. The reasons and prevent measures of forest fire induced breakdown of the transmission line were investigated, and the application of data analysis in this field was discussed in the present study. According to the data statistics on the forest fire induced breakdown of the transmission line, the occurrence of transmission line trip has apparent time and space rules. The flow chart of big data analysis on transmission line breakdown induced by forest fires with the data analysis was proposed. By using big data analysis, important information can be derived, which is helpful to the design of early-warning system, as well as the proper strategic decisions to control the damage of transmission line in forest fires.

Insulation Failure Mechanism of Cable in Fire Environment

In order to reveal the insulation failure mechanism of the cable under the fire condition, the conductive mechanism and aging mechanism of the cable insulation material were analyzed theoretically, and the relationship between the thermal decomposition weight loss curve and the insulation resistance and temperature of the cable insulation material was constructed. The results show that the reason for the failure of the cable in the fire is that the insulation performance of the insulating material decreases after heating. For different thermal aging degree of the cable, the decomposition process of insulating materials are divided into two stages. When the failure occurs, the insulating material is not decomposed; when the breakdown occurs, the insulating material is in the first stage of thermal loss. Therefore, the failure temperature of the cable can be considered mainly depends on the characteristics of its insulating material, regardless of the structure, shape and size of the cable.