25-08-2017, 09:32 PM
SCADA and Control Valves
SCADA and Control.pptx (Size: 1.04 MB / Downloads: 30)
What is SCADA..?
SCADA is “Supervisory Control and Data Acquisition” – real time industrial process control systems used to centrally monitor and control remote or local industrial equipment such as motors, valves, pumps, relays, sensors, etc.
SCADA is used to control chemical plant processes, oil and gas pipelines, electrical generation and transmission equipment, manufacturing facilities, water purification and distribution infrastructure, etc.
Industrial plant-scale SCADA is often referred to as a “Distributed Control System” or DCS
SCADA nuzzles up to embedded system issues, too.
system components of SCARDA
A SCADA System usually consists of the following subsystems:
A Human-Machine Interface or HMI is the apparatus which presents process data to a human operator, and through this, the human operator monitors and controls the process.
A supervisory (computer) system, gathering (acquiring) data on the process and sending commands (control) to the process.
Remote Terminal Units (RTUs) connecting to sensors in the process, converting sensor signals to digital data and sending digital data to the supervisory system.
Programmable Logic Controller (PLCs) used as field devices because they are more economical, versatile, flexible, and configurable than special-purpose RTUs.
Communication infrastructure connecting the supervisory system to the Remote Terminal Units.
Supervision vs. control
There is, in several industries, considerable confusion over the differences between SCADA systems and distributed control systems (DCS). Generally speaking, a SCADA system usually refers to a system that coordinates, but does not control processes in real time. The discussion on real-time control is muddied somewhat by newer telecommunications technology, enabling reliable, low latency, high speed communications over wide areas. Most differences between SCADA and DCS are culturally determined and can usually be ignored. As communication infrastructures with higher capacity become available, the difference between SCADA and DCS will fade.
Control valves
Control valves are valves used to control conditions such as flow, pressure, temperature, and liquid level by fully or partially opening or closing in response to signals received from controllers that compare a "set point" to a "process variable" whose value is provided by sensors that monitor changes in such conditions
Hardware solutions
SCADA solutions often have Distributed Control System (DCS) components. Use of "smart" RTUs or PLCs.
A functional block programming language, IEC 61131-3 (Ladder Logic), is frequently used to create programs which run on these RTUs and PLCs. This allows SCADA system engineers to perform both the design and implementation of a program to be executed on an RTU or PLC. A Programmable automation controller (PAC) is a compact controller that combines the features and capabilities of a PC-based control system with that of a typical PLC. PACs are deployed in SCADA systems to provide RTU and PLC functions. In many electrical substation SCADA applications, "distributed RTUs" use information processors or station computers to communicate with protective relays, PACS, and other devices for I/O, and communicate with the SCADA master in lieu of a traditional RTU.
Since about 1998, virtually all major PLC manufacturers have offered integrated HMI/SCADA systems, many of them using open and non-proprietary communications protocols. Numerous specialized third-party HMI/SCADA packages, offering built-in compatibility with most major PLCs, have also entered the market, allowing mechanical engineers, electrical engineers and technicians to configure HMIs themselves, without the need for a custom-made program written by a software developer.
SCADA Environment
In the old days, process control systems used proprietary protocols and ran with serial communications or even on physically separated private/dedicated networks
These days, process control systems often run on the enterprise LAN and over the Internet;
process control traffic may be
commingled with web pages,
email, P2P traffic, VoIP traffic, etc.