SCADA Systems are basically Supervisory Control and Data Acquisition systems. These are systems charged with data collection and its relaying to a central command for purposes of controlling and or managing a certain process. This data may be collected from sensors situated in a plant, factory or even far off installations. These systems are widely used in industry especially in this era of automation and increased efficiency. They are found in an assortment of industrial processes like power generation (both nuclear and other conventional methods), steel making, chemical processes and even nuclear fusion. Such plants have channels that may range from a few thousand to several thousand input/output. Such complex coordination of so many processes requires the use of the SCADA’s. These systems are being developed at an alarming rate with several SCADA’s capable of handling hundreds of thousands processes already being used by several industries.
There are only two documented cases of SCADA’s capable of handling one million input/output channels. They are currently in the final stages of development. These systems have several parts or components. These include the signal hardware (input and output), user interface (HMI), network, controllers, communication software and equipment. The term is used mostly when referring to the central command. The central command is charged with monitoring all data that is channeled in from sensors in the field some of which might be hundreds of mile away. The major components of such a system is composed of a master terminal unit or MTU also known as a central host or master station, a remote terminal unit or RTU which is charged with gathering data from the field and an entire station composed of custom software or standard software that is used to coordinate all the activities of the RTU’s as well as processing the data.
Most system operations are based on communication over long distances and they have open loop control characteristics. There are however specialized instances where they exhibit communication over short distances as well as closed loop tendencies. Distributed Control Systems (DCS) are found in treatment plants and factories and they might be mistaken for SCADA’s. The only difference being that DCS systems tend to have a more confined build as concerns their data gathering and control units.
Communication in DCS systems is mostly via LAN’s and is extremely fast and reliable. These systems employ a lot of closed loop control. A SCADA system will usually cover a huge area and makes use of less reliable communication systems.