Industrial Control Systems
Industrial control system (ICS) is a general term that encompasses several types of control systems, including supervisory control and data acquisition (SCADA) systems, distributed control systems (DCS), and other control system configurations such as skid-mounted Programmable Logic Controllers (PLC) often found in the industrial sectors and critical infrastructures.
Industrial control systems are typically used in industries such as electrical, water and wastewater, oil and natural gas, chemical, transportation, pharmaceutical, pulp and paper, food and beverage, and discrete manufacturing (e.g., automotive, aerospace, and durable goods.)
These control systems are critical to the operation of the U.S. critical infrastructures that are often highly interconnected and mutually dependent systems. It is important to note that approximately 90 percent of the nation’s critical infrastructures are privately owned and operated.
Keep in mind that actual implementations of industrial control systems may be hybrids that blur the line between DCS (Distributed Control Systems) and SCADA (Supervisory control and data acquisition) systems by incorporating attributes of both.
Overview of SCADA, DCS, and PLCs
Supervisory control and data acquisition (SCADA) systems are highly distributed systems used to control geographically dispersed assets, often scattered over thousands of square kilometers, where centralized data acquisition and control are critical to system operation.
They are used in distribution systems such as water distribution and wastewater collection systems, oil and natural gas pipelines, electrical power grids, and railway transportation systems. A Supervisory control and data acquisition (SCADA) control center performs centralized monitoring and control for field sites over long-distance communications networks, including monitoring alarms and processing status data.
Based on information received from remote stations, automated or operator-driven supervisory commands can be pushed to remote station control devices, which are often referred to as field devices. Field devices control local operations such as opening and closing valves and breakers, collecting data from sensor systems, and monitoring the local environment for alarm conditions.
Distributed Control Systems are used to control industrial processes such as electric power generation, oil refineries, water and wastewater treatment, and chemical, food, and automotive production. Distributed Control Systems are integrated as a control architecture containing a supervisory level of control overseeing multiple, integrated sub-systems that are responsible for controlling the details of a localized process.
Product and process control are usually achieved by deploying feed back or feed forward control loops whereby key product and/or process conditions are automatically maintained around a desired set point.
To accomplish the desired product and/or process tolerance around a specified set point, specific PLCs (Programmable Logic Controllers) are employed in the field and proportional, integral, and/or derivative settings on the PLC (Programmable Logic Controllers) are tuned to provide the desired tolerance as well as the rate of self-correction during process upsets.
DCS (Distributed Control Systems) are used extensively in process-based industries. Programmable Logic Controllers are computer-based solid-state devices that control industrial equipment and processes.
While Programmable Logic Controllers are control system components used throughout supervisory control and data acquisition and DCS (Distributed Control Systems) systems, they are often the primary components in smaller control system configurations used to provide operational control of discrete processes such as automobile assembly lines and power plant soot blower controls. Programmable Logic Controllers (PLCs) are used extensively in almost all industrial processes.
The process-based manufacturing industries typically utilize two main processes :
- Continuous Manufacturing Processes. These processes run continuously, often with transitions to make different grades of a product. Typical continuous manufacturing processes include fuel or steam flow in a power plant, petroleum in a refinery, and distillation in a chemical plant.
- Batch Manufacturing Processes. These processes have distinct processing steps, conducted on a quantity of material. There is a distinct start and end step to a batch process with the possibility of brief steady state operations during intermediate steps. Typical batch manufacturing processes include food manufacturing.
The discrete-based manufacturing industries typically conduct a series of steps on a single device to create the end product. Electronic and mechanical parts assembly and parts machining are typical examples of this type of industry.
Both process-based and discrete-based industries utilize the same types of control systems, sensors, and networks. Some facilities are a hybrid of discrete and process-based manufacturing.
While control systems used in distribution and manufacturing industries are very similar in operation, they are different in some aspects. One of the primary differences is that DCS or PLC-controlled sub-systems are usually located within a more confined factory or plant-centric area, when compared to geographically dispersed SCADA field sites.
Programmable Logic Controllers and Distributed Control Systems communications are usually performed using local area network (LAN) technologies that are typically more reliable and high speed compared to the long-distance communication systems used by SCADA (Supervisory Control and Data Acquisition) systems.
In fact, SCADA systems are specifically designed to handle long-distance communication challenges such as delays and data loss posed by the various communication media used. DCS and PLC systems usually employ greater degrees of closed loop control than SCADA (Supervisory Control and Data Acquisition) systems because the control of industrial processes is typically more complicated than the supervisory control of distribution processes.
These differences can be considered subtle for the scope of this document, which focuses on the integration of IT security into these systems. Throughout the remainder of this document, SCADA (Supervisory Control and Data Acquisition) systems, Programmable Logic Controllers and Distributed Control Systems will be referred to as Industrial control system (ICS) unless a specific reference is made to one (e.g., field device used in a SCADA system).
8 Responses to “Industrial Control Systems”
What is the most widely used LAN to share information on the SCADA network ?
Ethernet is the most widely used local area network (LAN) because it is cheap and easy to use.
What equipments you need to check in case of maintenance on a SCADA network ?
1) The RTU and component modules
2) Analog input modules
3) Digital input module
4) Interface from RTU to PLC (RS-232/RS-485)
5) Privately owned cable
6) Switched telephone line
7) Analog or digital data links
8) The master sites
9) The central site
10) The operator station and software
What is an RTU ?
RTU ( remote telemetry unit or remote terminal unit) is a stand-alone data acquisition and control unit, generally microprocessor based, that monitors and controls equipment at a remote location.
How many analog and digital signals have an RTU ?
1) small RTUs generally have less than 10 to 20 analog and digital signals
2) medium sized RTUs have 100 digital and 30 to 40 analog inputs
3) large sized RTU have more than 100 digital signals and 40 analog inputs
interesting post
a very good article about Industrial Control Systems