A SCADA system is common process automation system which is used to gather data from sensors and instruments located at remote site and to transmit data at a central site for either control or monitoring purposes. The collected data is usually viewed on one or more SCADA host computer located at the central or master site. Based on information received from remote stations, automated or operator driven supervisory command can be pushed to remote station control devices, which are often referred to as field devices.
Generally, a SCADA system includes the following components:
• Instrument that sense process variable.
• Local processor that collect data and communicate with he site’s instrument and operating equipment called Programmable (PLC), Remote Terminal Unit (RTU), Intelligent Electronic Device (IED), or Automation Controller (PAC).
• Short range communication between local processor, instrument and operating equipment. • Host computer as central point of human monitoring and control of the processes, storing databases and display statistical control charts and reports.
• Long range communications between local host computer using wired and of wireless network connections.
SCADA system differs from DCSs (Distributed Control Systems) which are generally found in plant sites. While DCSs cover the plant sites, SCADA systems cover much larger geographic areas.