SCADA stands for supervisory control and data acquisition. SCADA networks control and monitor the critical utility and process control infrastructures for manufacturing, production, and power generation for utility companies, including electricity, natural gas, oil, water, sewage, and railroads.
The development of SCADA can be traced back to the beginning of the 19 th century through the introduction of telemetry, which involves the transmission and monitoring of data obtained by sensing real-time conditions. Since the inception of telemetry, SCADA networks have become popular to control electrical and other infrastructure systems. An example of early telemetry is ComEd, one of the largest electric utility companies, that developed a system to monitor electrical loads on its power grid.
The following are common SCADA components:
• Remote terminal unit (RTU) A device used to convert analog and discrete measurements to digital information, such as an instruction to open a switch or valve.
• Intelligent electronic device (IED) A microprocessor-based controller that can issue control commands, such as to trip circuit breakers or raise or lower voltage levels if the IED senses voltage, current, or frequency anomalies. Some examples of IEDs are capacitor bank switches, circuit breakers, recloser controllers, transformers, and voltage regulators.
• Programmable logic controller (PLC) Very similar to an RTU in regard to operation, and may have additional intelligence through a real-time operating system (RTOS) with embedded I/O servers, and services such as SSH, FTP, and SNMP enabled.
• Human machine interface (HMI) The graphical representation (or GUI) of the control environment to the administrator.