Study On Fire Risk Assessment Of Urban Electric Power Cable Tunnel

With the rapid development of China's economy,the construction of urban infrastructure is received attention increasingly.Traditional urban transmission lines face many difficulties such as difficulty in maintaining and damaging the image of the city.Cable tunnel,as an underground construction,is suitable for the expansion and maintenance of transmission lines,and thus are well applied and spread among cities.However,urban electric power cable tunnels also face many safety problems,especially as an underground enclosed space,the fire problem in cable tunnel should not be ignored.Therefore,this thesis studies the fire risk and risk mitigation of urban power cable tunnels from the perspective of fire risk assessment.The main work and achievements are as follows:The key factors affecting the fire risk of urban electric power cable tunnels are analyzed.According to the characteristics of fire in urban cable tunnel,a hierarchical model of fire risk factors of urban power cable tunnels is constructed from the aspects of fire occurrence and consequences.Then,the factor weight calculation method combining TFN-AHP and entropy weight method is used to calculate the weight of the risk influenced factors.The result indicates that cable combustion properties,cable laying conditions,fire protection system configuration and power failure are the key factors that affect the fire risk of the cable tunnel.A quantitative fire risk assessment method for urban electric power cable tunnels is proposed.Combined with the risk associated factors that have been identified,a framework for quantitative fire risk assessment of urban power cable tunnels are proposed.The probabilistic simulation of fire in cable tunnel applies the method of combining with the Monte Carlo based parameter uncertainty analysis and the fire dynamic simulation,which in order to explicate the combination of probabilistic and deterministic of fire.On the other part,the cable tunnel fire risk analysis applies the fire scenario event tree model,and the results driven from the probabilistic simulation is used to quantify the occurrence probability and fire consequences of each scene,which in order to achieve the quantitative expression of fire risk.A case study on the risk assessment of electric power cable tunnel fire in a city is carried out.Based on the field investigation of electric power cable tunnels and the testing of typical power cable fire characteristics,a fire risk assessment of the power cable tunnel in a certain city is conducted.The calculation finds that the fire risk value of the cable tunnel is 2.23 × 10-2,which still has much place to improve.At the same time,the sensitivity analysis of different parameters in each scene finds that the fire brigade arrival time,personnel detection time,cable number and ignition source power are the sensitive factors influences fire risk.Therefore,four aspects to improve the fire risk control of urban power cable tunnels are recommended,include installing fire extinguishing system,shortening fire detection and fire rescue time,controlling fire load in the cable tunnel and protecting of cable joints.