Application of Structured Analysis Real Time Method on a Natural Gas Station Z. SALAH Université de Tunis, ESSTT, 5 Avenue Taha Hussein Montfleury 1008, Tunisie zaara.salah@yahoo.fr M.N LAKHOUA Université de Tunis El Manar, Ecole Nationale d'Ingénieurs de Tunis, LR11ES20 ACS, Tunisie MohamedNajeh.Lakhoua@enit.rnu.tn Abstract—The aim of this paper is to present the application of the method of structured analysis and real time (SA-RT) on a control-command application using supervisory control and data acquisition systems (SCADA). Then, the concepts of the SCADA system and its architecture are presented. An example of a control-command application of the supervision of the natural gas in a thermal power plant in Tunisia is presented and analyzed using the SA-RT formalism. Finally, this analysis enables us to facilitate the different steps of the programming and the configuration of the tabular in a SCADA environment. Keywords—SCADA architecture, structured analysis, real time, natural gas station. I. INTRODUCTION Supervisory control and data acquisition systems (SCADA) are widely used in industry for supervisory control and data acquisition of industrial processes. The process can be industrial, infrastructure or facility [1]. The SCADA system usually consists of the following subsystems [2]: • A Man-Machine Interface (MMI) is the apparatus which presents process data to a human operator, and through this, the human operator, monitors and controls the process. • A supervisory system, acquiring data on the process and sending commands to the process. • Remote Terminal Units (RTU) connecting to sensors in the process, converting sensor signals to digital data and sending digital data to the supervisory system. • Communication infrastructure connecting the supervisory system to the RTU. In fact, most control actions are performed automatically by RTU or by programmable logic controllers (PLC). Host control functions are usually restricted to basic overriding or supervisory level intervention. For example, a PLC may control the flow of cooling water through part of an industrial process, but the SCADA system may allow operators to change the set points for the flow, and enable alarm conditions, such as loss of flow and high temperature, to be displayed and recorded [3-5]. The feedback control loop passes through the RTU or PLC, while the SCADA system monitors the overall performance of the loop. The objective of this paper is to show interests of the use of SCADA systems in power systems. The next section briefly presents the different project management phases (identification of need; initiation; definition; design; acquisition and project closeout) of SCADA projects. Finally, we present and discus a case study of the architecture of a SCADA system in a thermal power plant. II. ARCHITECTURE OF A SCADA SYSTEM One of the effective tools in power network automation is the SCADA system [6]. In fact, the different equipments, including SCADA system, have been installed in many companies over the world in order to modernize their power system distribution networks [7-10]. In this part we present an example of the architecture of a SCADA system in a thermal power plant in Tunisia. So, we present on the one hand, the different steps of programming in a SCADA environment and on the other hand, the configuration of the tabular of the control-command application. In fact, the architecture of the SCADA system of a thermal power plant (Fig. 1) is constituted of following elements: • A plate of bornier; • FBM (Field Bus Module); • FCM (Field Bus Communication Module); • CP60 (Control process); • DNBT (Dual Node Bus base_T interface); • AW (Work Station Processor); • WP (Application Work Station). Among software of the SCADA system, we mention: • SYS MON: System monitor that supervises the good working of all the facilities of the system. • FOXVIEW: Interfacing operator to visualize the tabular with a slim rod to activate the main functions of the SCADA system. • FOX DRAW: creator of tabular. • FOX SELECT: Software permitting to reach the various elements of the hierarchy of the data base of the CP60. U.S. Government work not protected by U.S. copyright