Articles and technical notes ·
SCADA Systems Explained: Architecture and Applications
What SCADA is, its layers, where it is used and what to consider before planning a system.
SCADA (Supervisory Control and Data Acquisition) is a system that collects data from equipment in the field, shows it in a control center, raises alarms on out-of-range values and lets operators send commands back. It is common in water, energy, fuel and gas, transport and manufacturing, especially when sites are scattered or when many controllers have to be viewed in one place.
The typical architecture has four layers. In the field: sensors, transmitters and actuators (pumps, valves). Above them: controllers (PLCs) and remote terminal units (RTUs) that read them and operate them. The third layer is communication, for example over protocols such as Modbus, OPC UA or DNP3, on a cable, Ethernet, radio or a cellular network. The fourth layer is the SCADA server and the operator stations where the process is viewed.
A SCADA system has three core functions: real-time display of the state (level, pressure, flow, pump status); alarms with the point name and time; and logging data over time, so trends can be shown and events investigated afterwards. In addition it can send commands, for example to start a pump from the screen, with permissions and an audit trail.
Questions to settle before planning: how many points and sites there will be and how they will grow; which protocols the existing equipment speaks; whether a redundant (backup) system is needed; what cybersecurity requires, including separation between the control network and the corporate network; and how data will be stored and restored after a failure.
Our related articles continue with the cybersecurity of control systems and with upgrading an existing SCADA system to an open platform. To plan a system fitted to your site, contact the Teleris engineering team. This article is general and for explanation only.