Bosi Zhang

Investigation on effects of thickness on ignition characteristics and combustion process of the oil-impregnated transformer insulating paperboard

Effects of thickness on ignition characteristics and combustion process of the oil-impregnated transformer insulating paperboard were investigated experimentally by cone calorimeter. Five thicknesses of transformer insulating paperboard, including 0.5, 1.0, 1.5, 2.0 and 3.0xa0mm were taken into account together with five radiation intensities between 25 and 80xa0kWxa0m−2. According to the experimental results on ignition characteristics, the 0.5-mm paperboard for all radiation intensities and the 1.0-mm paperboard with the radiation heat flux less than 35xa0kWxa0m−2 were thermal thin material. The 1.0-mm paperboard under higher radiation intensities and the paperboard with the thicknesses of 1.5, 2.0 and 3.0xa0mm were thermal thick material. The heat release rate (HRR) of oil-impregnated transformer insulating paperboard decreased with its thickness. Due to the different pyrolysis processes, the number of HRR peaks increased with the thickness of paperboard. The CO and CO2 production rate and the O2 consumption rate were all decreased with the paperboard thickness basically. There was an increase in the CO production rate at the end of fire duration, since the incomplete combustion process occurred at this stage. The increase in the CO production rate was more obvious in the experiments under lower external radiation heat fluxes.

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.

Numerical Simulation on Smoke Propagation and Fire Separation in Electric Power Cable Tunnel

The smoke propagation process in an electric power cable tunnel was investigated numerically, and the effects of fire separation on the fire development were also explored. The numerical simulations were conducted by using the Fire Dynamics Simulation (FDS) in the present study. The electric power cable tunnel was insisted of four working wells and three tunnel sections, and the total length of this tunnel was 561 m. According to the simulation results, the smoke propagated fast in the electric power cable tunnel when there was no fire separation inside the tunnel, and the temperature of the whole tunnel increased obviously. The fire separation is an effective method to confine the fire smoke into one fire compartment. However, the flame would migrate in the whole fire compartment, mainly due to the lack of oxygen. The working well was affected by the high-temperature flame even the fire happened in the tunnel section. The temperature of the 2# working well reached almost 1000°C when the fire initially located at the 1# tunnel section in the present study.

Numerical Study on Fire characteristics in Force-Ventilated Compartment with different air inlet locations

The effects of air inlet locations on fire characteristics in force-ventilated compartment were investigated by computational fluid dynamics (CFD) simulations. The flame behaviour, the oxygen concentration above fire, the distribution of soot concentration and velocity of smoke in the closed compartment were discussed. The results show that the flame behaviour was mainly affected by the inflow air flow, and the flame inclined to the opened inlet in one-inlet scenario. The flame was found inclined to the exhaust vent in two-inlet scenarios. The difference between the soot concentrations in upper and lower space of the compartment was smaller in one-inlet scenarios compared with that in two-inlet scenarios, and the soot concentration was more uniform in the scenarios with higher air inlet elevation. The velocity of smoke on the side of inlet was larger than the other side in one-inlet scenario, which might cause stronger entrainment on the side with air inlet. In the two-inlet scenarios, the velocities of smoke on the sides of two air inlets were almost the same.

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.

Fire Performance Analysis of PVC and Cabtyre Cables Based upon the Ignition Characteristics and Fire Growth Indexes

The ignition characteristics and fire growth indexes of the PVC cable (Cable 1), the flame retardant PVC cable (Cable 2), the cabtyre cable (Cable 3), and the cabtyre cable with fireproof coating (Cable 4), were investigated experimentally. Twenty experiments were conducted by cone calorimeter, and the ignition time and fire growth index under different external radiation heat fluxes were focused primarily. Results showed that the ignition time of Cable 2 was longer than that of Cable 1, and the ignition time of Cable 4 was longer than that of Cable 3. The critical heat flux, under which the cable could be ignited for any length of time, was derived through data fitting. In the present study, the critical radiation heat fluxes for Cable 1–4 are 3.5, 9.5, 13.4 and 18.5 kW/m2. The ratio of peak heat release rate (HRR) to the time reached the peak HRR is defined as fire growth index. The fire growth index of Cable 1 is larger compared with that of Cable 2, and the fire growth index of Cable 3 is larger than that of Cable 4. The fire growth index of cables has well linear relationship with the external radiation heat flux in the present study.