Modelling and Evaluation of a Control Room Application.

This application paper describes the study of a control room system that has been performed inside the EU Artemis project HoliDes. The control room object of the study is for an Italian operator in gas energy distribution. Customers call the control room of the energy operator to signal malfunctioning of gas distribution and/or of gas apparatus. Upon a call the control room operators assign a technician delegated to physically reach the intervention site and make it, in first place, secure, and, in second place, back to normal operating condition. Because of the safety issues inherently associated with the gas distribution, the Italian Regulatory Authority for Electricity Gas and Water has set a service level agreement (SLA) requirement that states that an operator should reach the client site in less than 60 min in 95% of the times. This paper describes the Petri net models that have been used to assess what is the load of calls that can be dealt with without violating the SLA, and what type of conditions make the system in a critical state. Petri nets considered are colored stochastic Petri Nets with and without deterministic and generally distributed transitions. In modelling terms the main issue that has been faced is that of adequately represents the geographical distribution of calls and technicians, while the main issue for the computation of the performance indicator has been the SLA assessment, that requires a passage-time computation, an index that is not widely available in Petri net tools.