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SCADA

SCADA (Supervisory Control and Data Acquisition) systems are used in industrial and civil engineering applications to control distributed systems from a master location. SCADA is a very broad umbrella that describes solutions across a large variety of industries, including:

Electrical power distribution[?] grids and generation plants
Environmental control systems[?]
Traffic signals
Water management[?] systems

The broad architecture of a SCADA solution involves physical equipment such as switches, pumps, and other devices able to be controlled by an Remote Telemetry Unit (RTU). The RTU should also be able to read devices such as meters to assess the state of the equipment under its juristiction. The RTU is connected in some way to a set of master computers, usually in a control room. The dual roles of the master computers are to provide the information such as meter readings and equipment status to human operators in a digestable form and to allow the operators to control the field equipment in predefined ways.

While the SCADA Human-computer interface usually allows operators to view the state of any part of the plant equipment, most operator interaction with the system is driven by alarms. Alarms are automatically detected abnormal conditions in the plant equipment that require operator attention, and my require operator intervention to keep things running smoothly.

Since the early 1990s the role of SCADA systems in large civil engineering solutions has changed, requiring them to perform more operations automatically. Solutions sold as SCADA also often have Distributed Control System (DCS) components. Instead of relying on operator intervention, or master station automation, RTUs may now be required to operate on their own to control tunnel fires or perform other safety-related tasks. The master station software is required to do more analysis of data before presenting it to operators including Historical analysis and analysis associated with particular industry requirements. Saftey requirements are now being applied to the system as a whole, and even master station software must meet stringent safety standards for some markets.

SCADA systems have traditionally used combinations of radio and direct serial or modem connections to meet communication requirements.

This has also come under threat with some customers wanting SCADA data to travel over their pre-established corporate networks, or to share the network with other applications. The legacy of the early low-bandwith protocols remains, though. SCADA protocols are designed to be very compact and many are designed to send information to the master station only when the master station polls the RTU. Current standard SCADA products include Modbus, Conitel, and Dnp3. Many of these protocols now contian extensions to operate over TCP/IP, although it is good security engineering practice to avoid connecting SCADA systems to the Internet.