Research On Robustness Evaluation Of Urban Gas Pipeline Network Based On Cascade Failure

With the growth of the use time of most basic lifeline projects in China,the lifeline projects in many cities are facing the problem of component aging,especially the urban gas pipeline network.Urban gas pipeline network has high risk and importance to people’s life.In order to ensure the stability and safety of people’s production and life,the renovation,transformation or maintenance of urban gas pipeline network is necessary.However,in the gas pipeline network with interdependent nodes,the transformation or maintenance of nodes will make the nodes fall into a failure state.The failure of nodes may trigger the failure of associated nodes,resulting in cascade failure of gas pipeline network.Cascade failure has a significant impact on the gas pipeline network.Once it occurs,the robustness of the pipeline network will be greatly reduced,resulting in problems in the safety and operation of gas.At present,there is little research on the robustness of gas pipeline network at home and abroad,and there is still a vacancy in the research on the robustness of gas pipeline network under cascade failure conditions.This paper studies the robustness evaluation of urban gas pipeline network during reconstruction or maintenance,simulates the cascading failure condition of gas pipeline network by using the node deletion strategy of deliberately attacking key nodes,and constructs the pipeline network robustness evaluation model based on the perspective of cascading failure by evaluating the global efficiency of the network and the comprehensive importance of nodes.Firstly,in order to accurately identify the key nodes of the gas pipe network,this paper uses the space l network topology model to establish the topology of the gas pipe network.Based on the complex network theory,MATLAB software is used to calculate the node intermediate centrality,and the node degree centrality and intermediate centrality are used to construct the importance evaluation model of the node structure of the gas pipe network;The entropy theory is introduced,the node flow entropy is defined,and the TGNET software is used for hydraulic simulation to construct the evaluation model of node gas supply importance of gas pipeline network;Considering the influence of nodes on the structural damage resistance and gas supply reliability of gas pipeline network,the comprehensive importance evaluation model of nodes is constructed through the importance of node structure and gas supply.Then,based on the node deletion strategy of deliberate attack,this paper selects the key nodes in the gas pipeline network and applies simulation deletion to them.The cascading failure model is constructed by using the Coupled Mapping Lattice(CML)method.The cascading failure conditions under the failure of different key nodes of the gas pipeline network are simulated by TGNET software.The parameters of network global efficiency and node importance are introduced to reflect the overall and individual properties of the pipeline network respectively,The robustness evaluation model of gas pipeline network is constructed to analyze and evaluate the robustness performance of gas pipeline network under different cascade failure conditions.Finally,the robustness of a city’s regional gas pipeline network under cascade failure is evaluated and analyzed.According to the performance of robustness under different cascade failure conditions,based on the idea of prior defense,three key strategies such as trusted node strategy,key protection strategy and adding gas source strategy are proposed.The robustness of the pipeline network under the key strategy is compared with that of the original pipeline network to illustrate the effectiveness of the strategy,At the same time,a general pipeline network robustness improvement strategy for pipeline network function optimization and design optimization is proposed.Through the case study,it is found that the node importance evaluation model considering flow entropy can accurately and comprehensively identify the key nodes of gas pipeline network,and the result is reliable;Adding a new gas source at the downstream of the key node identified by a ring branch gas pipeline network can reduce the average value of the final cascade failure scale to 0.266 times of the original scheme,so as to weaken the cascade failure scale under the failure of key nodes and significantly improve the robustness of the pipeline network.This study provides a favorable basis for identifying the key nodes of gas pipeline network and avoiding the risk of pipeline robustness loss caused by cascade failure,and provides guiding suggestions for the renovation and reconstruction project of gas pipeline network.