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Supervisory Control & Data Acquisition  (SCADA)

SCADA refers to industrial control systems (ICS) that are employed to control and keep track of equipment or a plant in industries like water and waste control, telecommunications, energy, transport, paper, and oil and gas refining. SCADA is a computer system used to gather and analyze real-time data. Control actions are performed automatically by RTUs or by PLCs. Host control functions are usually restricted to basic overriding or supervisory level intervention. For example, a PLC may control the flow of cooling water through part of an industrial process, but the SCADA system may allow operators to change the set points for the flow, and enable alarm conditions, such as loss of flow and high temperature, to be displayed and recorded. The feedback control loop passes through the RTU or PLC, while the SCADA system monitors the overall performance of the loop. This data is processed by the computer and is presented on a regular basis. SCADA also saves and make logs for every event into a log file that is saved on a hard drive or is sent to a printer. SCADA gives warnings by sounding alarms if situations develop into hazardous scenarios. SCADA systems were initially employed in the 1960s. They include both software and hardware components. The hardware collects and enters data into a computer with SCADA software.  SCADA systems consist of: • Field data interface equipment, generally programmable logic controllers (PLCs) or remote terminal units (RTUs). These connect to field sensing devices, local control switchboxes and valve actuators. Field-data-interface equipment forms the core part of SCADA systems. • A communications system. This is employed to move data between different pieces of field data interface equipment and control units, and the computer systems employed in the SCADA central host. The system may be telephone, radio, satellite, cable, etc or a combination of any of these. The communications network is designed to offer the way by which the data can be transmitted in between the field-based RTUs and the central host computer servers. • A central host computer server(s). This is often known as a master station, a SCADA center, or a master terminal unit (MTU). The central host computer is usually a single computer or a computer server network. • A set of standard and/or customized software systems. They are helpful in delivering the operator terminal application and SCADA central host. This supports the communications system, and monitors and controls the remotely located field-data-interface equipment. Some of the software products usually used within the SCADA system include: • Central host computer OS • Operator terminal OS • Central host computer application • Operator terminal application • Communications protocol drivers • RTU automation software • Communications network management software
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