SCADA refers to a centralised system, which is meant to monitor and control complex industrial systems distributed over an extensive area. A typical SCADA system can act as a decisive link between an industrial plant and its distribution network. Say for example, a typical SCADA system will ensure adequate functioning of a power plant and the distribution network of national power grids.
SCADA control functions
The host control functions of SCADA systems are usually restricted to supervisory level interventions. Say for example, a typical PLC system may be used to control the flow of coolant to a section or the plant, whereas a SCADA system will enable the operators to alter the set points to plan the flow and set alert conditions to be recorded. The major advantage of SCADA is that it enables remote administration, which when integrated with PLC makes management of a large plant just a breeze.
A typical SCADA system comprises of many subsystems as;
An HMI (Human-Machine Interface), which is an apparatus that processes data for the human operators to take informed decisions.
A computer system to acquire data and process it to send commands.
Remote terminal unit/s (RTUs), which ideally connects to the sensors to access the signals and convert it to digital data to be sent to the supervisory system.
Programmable Logic Controllers (PLCs), which are field devices for various purposes that can be customised based on purpose.
Communication infrastructure to connect the supervisory system to remote terminal units to access data and transfer information.
SCADA systems are usually comprised of a widely distributed database that is known as tag database. Such databases are made of elements called tags or points. An element represents a single input or output (I/O) value, which is monitored or controlled using the central system.
Overtime, SCADA systems are largely advanced and now there are web-based and cloud-based SCADA applications to ensure more flexibility, customisability, and these also eradicate the previous restrictions on geographical restrictions, time constraints, and accessibility.