Supervisory Control and Data Acquisition

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A whole family of terms denote the accessing of measuring devices, automated analysis, human understandable display and interactive control, and the control of actuators, such as: Industrial Automation and Control Systems, Industrial Control Systems, Process Control Systems, Supervisory Control and Data Acquisition, and Distributed Control Systems.

Definitions

Other International Definitions

International Society of Automation (ISA)

A generic name for a computerized system that is capable of gathering and processing data and applying operational controls over long distances. Typical uses include power transmission and distribution and pipeline systems. SCADA was designed for the unique communication challenges (delays, data integrity, etc.) posed by the various media that must be used, such as phone lines, microwave, and satellite. Usually shared rather than dedicated [1].


Standard Definition

NIST

SCADA systems are highly distributed systems used to control geographically dispersed assets, often scattered over thousands of square kilometers, where centralized data acquisition and control are critical to system operation. They are used in distribution systems such as water distribution and wastewater collection systems, oil and natural gas pipelines, electrical power grids, and railway transportation systems. A SCADA control center performs centralized monitoring and control for field sites over long-distance communications networks, including monitoring alarms and processing status data. Based on information received from remote stations, automated or operator-driven supervisory commands can be pushed to remote station control devices, which are often referred to as field devices. Field devices control local operations such as opening and closing valves and breakers, collecting data from sensor systems, and monitoring the local environment for alarm conditions [2].

SCADA systems consist of both hardware and software. Typical hardware includes an MTU placed at a control center, communications equipment (e.g., radio, telephone line, cable, or satellite), and one or more geographically distributed field sites consisting of either an RTU or a PLC, which controls actuators and/or monitors sensors. The MTU stores and processes the information from RTU inputs and outputs, while the RTU or PLC controls the local process. The communications hardware allows the transfer of information and data back and forth between the MTU and the RTUs or PLCs. The software is programmed to tell the system what and when to monitor, what parameter ranges are acceptable, and what response to initiate when parameters change outside acceptable values. An IED, such as a protective relay, may communicate directly to the SCADA Server, or a local RTU may poll the IEDs to collect the data and pass it to the SCADA Server. IEDs provide a direct interface to control and monitor equipment and sensors. IEDs may be directly polled and controlled by the SCADA Server and in most cases have local programming that allows for the IED to act without direct instructions from the SCADA control center [2].

SCADA systems are usually designed to be fault-tolerant systems with significant redundancy built into the system architecture[2].

See also


Notes