What are Distributed Control Systems (DCS)

Distributed Control Systems

What are Distributed Control Systems (DCS)
Various systems are introduced to automate the processes in the manufacturing industry and minimize the human interaction with the machines. These systems not only save the cost but also keep the injuries to minimum. Distributed processes are controlled by decentralized elements in a distributed control system or DCS.

Routine operations are carried out without the need of user intervention. There is an interface known as SCADA (Supervisory Control and Data Acquisition) which lets the user interact with the system. A DCS consists of a remote and a central control panel with a communication medium. Two different names are given to the remote control panels by different suppliers. The names are

1)    Remote transmission Unit or RTU
2)    Digital Communication Unit or DCU

The functions of these remote units are same as they contain I/O modules and communication mediums and processors. These remote control units can be connected to the central control panel or SCADA with the help of a wireless or wired connection.
The software used to read the I/O command is of specialized nature.

Fig - A DCS System with 700 IO's

A detailed analysis of network protocols is required before the selection of DCS is finalized. The systems differ in terms of applications and complexity and the applications depend on the implementation of the system. A DCS with smaller implementation may only consist of a single Programmable Logic Controller or PLC. This controller will be connected to a computer in the remote office.

PLC is also an attribute of the large and complex DCS installations like in electrical grids and in power generation fields. They are also widely used in water treatment plants and in systems for environmental control. Petroleum refineries and petrochemical industry also uses these systems on a mass scale as these are intelligent systems and save all the process data necessary to continue the operations in case of a communication failure.