1 - Introduction

Abstract

The chapter discusses the supervisory control and data acquisition (SCADA) systems. The chapter describes SCADA as the combination of telemetry and data acquisition techniques, and explains the way it works. SCADA collects information via a remote terminal unit (RTU), transfers it back to the central site, performs necessary analysis and control, and then displays that information on a number of operator screens or displays. The required control actions are then conveyed back to the process. The RTU provides an interface to the field analog and digital sensors situated at each remote site. SCADA software can be divided into two types—proprietary or open. Companies develop proprietary software to communicate to their hardware, and these systems are sold as “turnkey” solutions. Open software systems have gained popularity because of the interoperability they bring to the system. SCADA master stations and RTUs are increasingly using components of local area networks (such as Ethernet) and Transmission Control Protocol/Internet Protocol (TCP/IP) in the communications of the real time data. Although the open systems interconnection model is generally preferred, a simplified model called the TCP/IP reference model is used that consists of the four layers—network interface layer, Internet layer, service layer, and application layer.