Performance Assessment Of The Lifeline Network Considering Dependencies

Lifeline systems,such as transportation system,communication system,water supply system,oil transportation system,gas transmission system and power transmission system,are the bases for the maintenance and development of the modern civilized society.With the great progress of information technology,the dependencies among lifeline systems have been continuously improved,which makes the lifeline systems evolve into lifeline network systems having complex adaptive systems characteristics in essence.In recent years,some famous natural disasters or intentional attacks have witnessed the spread and amplification phenomenon of the initial damages or destructions among the lifeline systems,such as the "911terrorist attacks" in 2001,the "hurricane Katrina" in 2005 and the "Wenchuan earthquake" in 2008.Only by fully considering the dependencies among lifeline networks can we more accurately evaluate the performance and vulnerability of Lifeline Networks under disaster factors.Previous studies mostly focused on single lifeline network.Therefore,it is of great significance to study the related issues of lifeline networks based on the dependencies among lifeline networks.Lifeline networks are not allowed or unrealistic to analyse their overall behaviors under disasters by direct large-scale damage test.Therefore,the simulation method is an important method to study the lifeline networks under different disasters.However,many problems have not been solved well,such as the disastrous model of disasters,the establishment of different levels of dependencies among lifeline networks,the spreading mechanism of initial disruption and the fast calculation of lifeline network reliability.This paper studies the above problems,the main research contents are as follows:(1)In this dissertation,an energy system including the oil transportation and storage system and power transmission system in Daqing Oilfield is selected as the research object.The oil system is abstracted as oil network,which has oil gathering stations,joint stations,tank farms and the the buried pipelines among them;the power system is abstracted as power network having higher voltage substations,lower voltage substations,power plants and the overhead transmission lines among them.The directed edges within different networks directly represent the inherent dependencies of the connected nodes.Each node of the oil network needs power from the lower substations of the power network to operate;according to the results of the survey,a series of function-dependent node pairs are constructed,and the interdependence between networks is expressed as the conditional probability of node failure of the oil network under the node failure condition of the lower substation in the power network,and added as a virtual edge to the oil transportation Network and transmission network,and then build a lifeline network overall system that covers the different levels of dependencies among the two networks.(2)Based on the characteristics of small-scale damage,a man-made attack attenuation model is proposed.Relative network indicators reflecting the changes of the lifeline network are designed from two aspects: topology and resource flow.The performance and vulnerability of the target lifeline network under different functional dependencies among networks is simulated.The method of identifying the key nodes of lifeline network is designed on the basis of the proposed man-made attack attenuation model,which expands the previous ideas that identify the key nodes by removing nodes or edges only.The proposed method is verified by the failure of La 14 th substation during the Lindian earthquake in 2005,and the numerical simulation results of the target node are in good agreement with the actual results when the level of functional dependency between networks is equal to or greater than 0.75,which not only verifies the design of the key indicators,but also verifies the feasibility of this method.(3)Taking Lindian earthquake as an example,the influence of large-scale damage on the lifeline network is studied,and the method of analyzing the performance and vulnerability of the lifeline network under different functional dependencies is proposed.Through the simulation of the Lindian earthquake in 2005,the results show that the simulated loss of earthquake damage agrees well with the actual loss of the lifeline network caused by the earthquake,which verifies the feasibility and scientificity of the proposed method.It also shows that the proposed method is more reliable on lifeline network loss prediction.(4)This paper proposes and implements a method for calculating the lifeline network reliability based on the equivalent network,and several classic lifeline networks are selected for calculating,and compared with other classic reliability calculation methods.For the reliability problems of 3 × 100 mesh networks at both ends,accurate results can be obtained within 28.04 s while other methods can not calculate,which shows the feasibility and efficiency of the proposed method.