SCADA system is fundamentally a control system which is used for supervision and managing upper level processes. For this purpose, various computers, data communications and visual user interfaces are used. SCADA stands for supervisory control and data acquisition. Some other exterior devices are also used including PLCs and PID controllers so that an interface is provided for operation of the hardware. The operator is able to monitor and issue all commands related to the process including changes in controller set point using provided interfaces. This is all taken care of by using the SCADA system for supervision. But it must be noted that all of real-time calculations in terms of the logic or the controller are done by the specialized modules that are connected to devices such as sensors and actuators.
The concept of the SCADA system came into being when need for a remote access arose and that too to numerous local control modules. These modules were not required to be from the same manufacturers and could be very different, but the access would be allowed using standard automation protocols. In terms of practical usage, there is much resemblance between distributed control systems and SCADA systems when it comes to functionality. However, there’ll be more than one way to achieve this communication with the plant. The benefit is that a number of large-scale processes can be controlled even when they are spread out over multiple cities and extensive distances. When it comes to control systems for the industry, these types of systems are the most used systems but a disadvantage is that SCADA systems are allegedly prone to vicious attacks of cyber-warfare and/or cyber-terrorism.
The fundamental characteristic of SCADA system is that it can be used to supervise and operate a large range of other exclusive devices.
Following is a description of the generic model of the system in which central manufacturing levels are managed through computerized control.
The devices at level 0 are classified as devices of the field. They include flow and temperature transducers, ultimate control components i.e. control valves.
The components at Level 1 are basically the modules for input and output. They are industrialized modules which have their own set of affiliated electronic processors.
The components of Level 2 are known as the supervisory computers. Their job is to collect information that is provided by the processor nodes that are part of the system and supply the operator control screens.
Level 3 is known as the control level in terms of production. The purpose of this level is not to have direct control of the process but to ensure monitoring of the productions and targets to achieve.
Level 4 is known as the scheduling level for the productions.
A large variety of both small-scale and large-scale systems can be constructed by this SCADA concept. There are no limitations on the scale of the systems and they can take more than tens to thousands of process loops. All of this functionality is dependent upon the type of application. There are various examples which are categorized as industrial, infrastructure and processes that are based on facility.