A distributed control system (DCS) is a digital automated industrial control system (ICS) that uses geographically distributed control loops throughout a factory, machine or control area. Unlike a centralized control system that operates all machines, a DCS allows each section of a machine to have its own dedicated controller that runs the operation. A DCS has several local controllers located throughout the area that are connected by a high-speed communication network. While each controller works autonomously, there is central supervisory control run by an operator.
DCS are used to control industrial processes and increase their safety, cost-effectiveness and reliability.
DCS are commonly used in serval processes, including:
- Chemical plants
- Petrochemical (oil) and refineries
- Nuclear power plants
- Water treatment plants
- Sewage treatment plants
- Food processing
- Automobile manufacturing
- Pharmaceutical manufacturing
A DCS includes both software and hardware elements. Installation costs are minimized by the simplicity of local installation with most controllers. Reliability is improved by onsite, low-latency automated control; human oversight is enabled for central control functions and remote control options. Individual processes have their own controllers with separate CPUs, so other processes can continue in an individual failure situation, unlike a central controller system.
A DCS is functionally similar to today’s supervisory control and data acquisition (SCADA). SCADA is also used in power plants, oil and gas refining, telecommunications, transportation, and water and waste control. SCADA tend to be used in situations where the control center is more remotely located.
Other ICS technologies include industrial automation and control systems (IACS), programmable logic controllers (PLCs), programmable automation controllers (PACs), remote terminal units (RTUs), control servers, intelligent electronic devices (IEDs) and sensors.