What are the difference between DCS and SCADA?

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Difference Between DCS and SCADA

What is DCS?

DCS stands for Digital Controlled System, and it is also called as Distributed Control System. It is considered as the brain of the control system.

The DCS is a control system that collects data from the field and chooses what to do with it. Data collected in the field can be saved for future reference, used for simple process control, or combined with data from other parts of the plant to create advanced control plans.

The Distributed Control System (DCS) is used to monitor and control equipment that requires remote manual intervention.

How a DCS used?

Although the DCS process is used to oversee complex manufacturing processes in many regulatory industries, it is commonly used in large, continuous manufacturing plants, such as in the petrochemical industry. These and other manufacturers can efficiently coordinate settings from top to bottom using a centralized computer network with the help of DCS. When configured properly, DCS can improve safety and productivity.

How does a DCS work?

We use sensors and gauges in the field to receive and transmit the information. These gauges and sensors convert the information from the field instruments into an electric signal and are sent it to a control room somewhere in the field. The signal in this control room can be converted to pressure, flow rate, concentration, temperature, or level using programmable logic. This logic controls the process and receives the signal, comparing the set point given by the operator with or without the field and sending a signal to the artificial variables in the field.

Important Features of DCS

The important features of the distributed control system are:

• Management of complicated processes
• System redundancy
• Numerous pre-defined functional blocks – DCS provides various algorithms, many standard application libraries, pre-defined and pre-tested activities to handle huge systems
• More advanced HMI design allows to manage and monitor complex systems and also this functions as a centralized system of the entire DCS.
• Enhanced scalability – The DCS structure allows more flexibility which can be used for any range of server systems
• System protection

Advantages of DCS System :-

• DCS allocate flexibility and simplicity by allowing central control
• Monitoring and reporting of individual components and processes
• DCS are scalable
• Possible to control through dynamic graphic
• Eliminating human error by Logging of data

Disadvantages of DCS system

• Failure of one controller effects more than one loop
• DCS required skilled operator because the all information hidden behind CRT

What is SCADA?

SCADA Stands for Supervisory Control and Data Acquisition. SCADA is a set of software and hardware components that enables industrial firms to:

• Control industrial processes on a local or remote level.
• Real-time data is monitored, gathered, and processed.
• Human-machine interface (HMI) software allows you to communicate directly with equipment including sensors, valves, pumps, motors, and more.
• Create a log file to keep track of events.

The main purpose of SCADA is to monitor and control systems from the central site, alarm plant, or local operating system. Although override control is available, it is rarely used; Instead, SCADA regularly changes control setpoints.

How SCADA works?

The maximum fundamental SCADA gadget is a graphical person interface (GUI) related to a programmable common sense controller (PLC) inside a production plant or an automatic manufacturing unit. Most SCADA architectures include server computer systems that contact/communicate with devices and a GUI related to the server. The servers and the GUI may be placed either on-site or remotely relying on the character of the plant being monitored and controlled.

The SCADA tool community is made of RTUs (Remote Terminal Units) and PLCs. Both RTUs and PLCs use microprocessors to have interacted and communicate with the field devices. Field devices can consist of pumps, valves, motors, and any human-device interface.

The microprocessor in the RTU and the PLC collects data from the field devices and transmits it to the SCADA server software, where it is recorded and analyzed, and then displayed in the GUI.

Prior to SCADA, processing plants or manufacturing units may require additional on-site personnel to perform and supervise commercial equipment. If equipment is at risk of overheating or malfunctioning, staff will use the selector switch to manually adjust the output after reading the analog data through a series of dials. They might additionally oversee the shutting down of equipment and resetting of instruments.

With the SCADA system, the demand for on-site personnel is greatly reduced and on-site personnel can focus on the most important tasks Data may be accrued and accumulated from throughout the globe, permitting operators to make extra knowledgeable selections and optimize output. Costly manufacturing slowdowns also can be avoided with predictive analytics and preventative maintenance.

Advantages of SCADA

• Large number of data can be stored and processed
• Fast in obtaining a response
• Due to the optimization of the factory, it improves the energy-saving effect.
• It reduces the time for fault identity and restoration.
• Receiving real-time information to monitor equipment

Disadvantages of SCADA

• Overhead IP performance
• Web-enabled SCADA managed users for remote monitoring
• Control remote sites through a Web browser Security issues. The
• PLC-based SCADA system is very complicated in terms of hardware units and related modules.

DCS vs SCADA

A table comparing Distributed Control Systems (DCS) to SCADA systems

Feature	Distributed Control System (DCS)	Supervisory Control and Data Acquisition (SCADA)
Definition	A network-based process control system that connects sensors, controllers, operator terminals, & actuators.	A system for remote monitoring & control that uses coded signals via communication channels.
Architecture	Hierarchical & closed-loop control.	Hierarchical & open-loop control.
Main Components	Human-machine interface (HMI), controllers, I/O modules, and engineering workstations.	Infrastructure for communication, HMI, PLCs, and remote terminal units (RTUs).
Primary Use	Process control is used in the chemical, oil & gas, pharmaceutical, and power generation industries.	Infrastructure monitoring and control includes water supply systems, electrical grids, & pipelines.
Complexity	Typically more complicated due to close integration and extensive control strategies.	It is less difficult because it focuses mostly on data collecting and basic control.
Geographical Span	Usually limited to one plant or region.	Can encompass enormous geographical areas, frequently over multiple sites.
Data Acquisition	Concentrate on real-time data collecting and control.	The primary focus is on data collecting, which can occasionally be done in near real time.
Control Capability	Provides superior process control & automation.	Basic control is frequently employed for supervisory-level monitoring.
Redundancy and Reliability	High redundancy & reliability for the continuous process operations.	Typically lower redundancy, varies on application & criticality.
Cost	Generally more expensive due to complexity & critical nature of applications.	Often less expensive, especially for the systems covering large areas.
Scalability	Scalable, but only inside a specific plant or area.	Highly scalable to cover large areas with several sites.
Integration	Excellent integration with process control &management systems.	Communication protocols enable effective integration with a wide range of sensors and control devices.
Communication	Proprietary communication protocols are frequently used to ensure reliability and security.	To provide flexibility, a combination of proprietary & standard protocols (such as Modbus and DNP3) are used.
Human-Machine Interface	Advanced HMI with complete control and monitoring capabilities.	HMIs are primarily concerned with providing supervisory control & visualization.