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    1 : SCADA and Control Valves Muhammad Zeeshan EE-01083-089 Sec => A The University Of Lahore
    2 : 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.
    3 : 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.
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    5 : 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.
    6 : 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
    7 : Systems WORKING The term SCADA usually refers to centralized systems which monitor and control entire sites, or complexes of systems spread out over large areas (anything between an industrial plant and a country). Most control actions are performed automatically by Remote Terminal Units ("RTUs") or by programmable logic controllers ("PLCs"). Host control functions are usually restricted to basic overriding or supervisory level intervention. For example, a PLC may control the flow of cooling water through part of an industrial process, but the SCADA system may allow operators to change the set points for the flow,and enable alarm conditions, such as loss of flow and high temperature, to be displayed and recorded. The feedback control loop passes through the RTU or PLC, while the SCADA system monitors the overall performance of the loop.
    8 : Human Machine Interface
    9 : Data acquisition begins at the RTU or PLC level and includes meter readings and equipment status reports that are communicated to SCADA as required. Data is then compiled and formatted in such a way that a control room operator using the HMI can make supervisory decisions to adjust or override normal RTU (PLC) controls. Data may also be fed to a Historian, often built on a commodity Database Management System, to allow trending and other analytical auditing.
    10 : A Human-Machine Interface or HMI is the apparatus which presents process data to a human operator, and through which the human operator controls the process. An HMI is usually linked to the SCADA system's databases and software programs, to provide trending, diagnostic data, and management information such as scheduled maintenance procedures, logistic information, detailed schematics for a particular sensor or machine, and expert-system troubleshooting guides. The HMI system usually presents the information to the operating personnel graphically, in the form of a mimic diagram. This means that the operator can see a schematic representation of the plant being controlled. For example, a picture of a pump connected to a pipe can show the operator that the pump is running and how much fluid it is pumping through the pipe at the moment. The operator can then switch the pump off. The HMI software will show the flow rate of the fluid in the pipe decrease in real time. Mimic diagrams may consist of line graphics and schematic symbols to represent process elements, or may consist of digital photographs of the process equipment overlain with animated symbols.
    11 : 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.
    12 : SCADA architectures SCADA systems have evolved through 3 generations as follows: First generation: "Monolithic“ In the first generation, computing was done by mainframe systems. Networks didn’t exist at the time SCADA was developed. Thus SCADA systems were independent systems with no connectivity to other systems. Second generation: "Distributed“ he processing was distributed across multiple stations which were connected through a LAN and they shared information in real time. Each station was responsible for a particular task thus making the size and cost of each station less than the one used in First Generation. Third generation: "Networked“ hese are the current generation SCADA systems which use open system architecture rather than a vendor-controlled proprietary environment. The SCADA system utilizes open standards and protocols, thus distributing functionality across a WAN rather than a LAN.
    13 : Effects Associated with SCADA Related Incidents direct problems discharge of a pollutant, destruction of property, fatalities indirect problems as in the case of a loss of power: the power failure may not directly cause damage, but its absence may make it impossible for businesses to operate 2nd order effects resulting from the cascading failures, e.g., loss of power might cause still other critical systems to fail and so on
    14 : SCADA Security The industry has generated a large base of relatively insecure systems, with chronic and pervasive vulnerabilities that have been observed during security assessments. Security for SCADA is typically five to ten years behind typical information technology (IT) systems
    15 : 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.
    16 : Windows-Based Control Stations SCADA devices are often controlled from central monitoring stations (MTUs, or “master terminal units”). Historically those were Unix-based systems, but many contemporary MTUs are now Microsoft Windows based.
    17 : Scada communication
    18 : Plain Text (Unencrypted) Traffic Plain text transmissions are still very common in the SCADA world. One notable exception: the AGA/GTI SCADA Encryption initiative… In the realtime world, encryption overhead and jitter may be problems to overcome… All Traffic Is On Just One Port In many cases, SCADA traffic will be on just one port such as 502/tcp
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