Modeling and Evaluation of Maintenance Procedures for Gas Distribution Networks with Time-Dependent Parameters

Gas networks comprise a special class of infrastructure, with relevant implications on safety and availability of universal services. In this context, the ongoing deregulation of network operation gives relevance to modeling and evaluation techniques supporting predictability of dependability metrics. We propose a modeling approach that represents maintenance procedures as a multi-phased system, with parameters depending on physical and geographical characteristics of the network, working hours, and evolution of loads over the day. The overall model is cast into a non-Markovian variant of stochastic Petri nets, which allows concurrent execution of multiple generally distributed transitions but maintains a complexity independent of network size and topology. Solution is achieved through an interleaved execution of fluid-dynamic analysis of the network and analytic solution of the stochastic model of the procedure. Solution provides availability measures for individual sections of the network as well as global quality of service parameters.