artificial intelligence

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SCADA

• SCADA stands for Supervisory Control and Data
  Acquisition. SCADA refers to a system that
  collects data from various sensors at a factory,
  plant or in other remote locations and then sends
  this data to a central computer which then
  manages and controls the data.
• The feedback control loop passes through the
  remote terminal unit(RTU) or Prgrammable logic
  controller (PLC), while the SCADA system monitors
  the overall performance.
• For example
• A PLC may control the flow of cooling water
  through part of an industrial process, but the
  SCADAsystem 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.
• Most essentially the SCADA system consists of
  three fundamental components (i.e. Master station
  (MS) or Central Monitoring System (CMS),
  Communication link and RTU or PLC).
• A Central Monitoring System (CMS), contained
  within the plant and one or more Remote Stations.
  The CMS houses the Control Server and the
  communications routers via a peer-to-peer
  network. The CMS collects and logs information
  gathered by the remote stations and generates
  necessary actions for events detected. A remote
  station consists of either a Remote Terminal Unit
  (RTU) or a
• Programmable Logic Controller (PLC) which
  controls actuators and monitors sensors.

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Typically, remote stations have the added
capability to be interfaced by field operators
via hand held devices to perform diagnostic and
repair operations. The communications network is
the medium for transporting information between
remote stations and the MS. This is performed
using telephone line, cable, or radio frequency.
If the remote site is too isolated to be reached
via direct radio signal, a radio repeater is used
to link the site. Simulation tools used to aid
the operator in preventing disturbances. Simulatio
n is used when the system which is to be analyse
or design is complex to use analytical techniques
(like aerodynamics). Simulation models can be
descriptive and physical. Simulation models that
are formulated called descriptive
models. Physical models mostly are time-discrete
showing the act and interact of entities of a
system. These models can be built after many
steps involving computer programs. The state of
the system changes as a consequence of events in
the system . These events are considered to occur
at discrete times models are called discrete
event simulation models. Simulation languages
Most well-known simulation languages are GASP
IV, GPSS and SIMSCRIPT II.1
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The process can be Industrial include those of
manufacturing, production, power generation,
fabrication, and refining, Infrastructure
include water treatment and distribution,
wastewater collection and treatment, oil and gas
pipelines, electrical power transmission and
distribution, and large communication systems.
Facility based including buildings,
airports, ships, and space stations. They monitor
and control HVAC, access, and energy consumption.
HVAC "heating, ventilating, and air
conditioning" is sometimes referred to as climate
control Little More About SCADA A SCADA system
manages electricity distribution by collecting
data from, and issuing commands to,
geographically remote field control stations from
a centralized location. In the Oil and Gas
industry, refining and processing facilities use
distributed control systems (DCS) while holding
facilities and distribution systems utilize SCADA
technology. The water supply infrastructure
utilizes DCS for the processing operations but
use SCADA technology for distribution operations.
A waste treatment plant runs similar to that of
the water supply infrastructure.
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Suppose you have a simple electrical circuit
consisting of a switch and a light. Like
this This circuit allows an operator to watch
the light ( ) and know whether the switch is open
or closed. The switch may indicate that a motor
is running or stopped, or whether a door is open
or closed, or even whether there has been a fault
or the equipment is working. So far there is
nothing special about this. But now imagine that
the switch and the lamp were 100 kilometres
apart. Obviously we couldn't have an electrical
circuit this large, and it would now be a problem
involving communications equipment Now
complicate the problem a bit further. Imagine we
had 2000 such circuits. We could not afford 2000
communications circuits. However someone found
that we could use one communications circuit by
sharing it. First we send the status (open/closed
or 0/1) of the first circuit. Then we send the
status of the second circuit, and so on. We need
to indicate which circuit the status applies to
when we send the data. The poor operator at the
other end still has a problem. He has to watch
all 2000 circuits. To simplify his task, we could
use a computer. The computer would monitor all
circuits, and tell the operator when he needs to
look at a particular circuit. The computer will
be told what the normal state of the circuit is
and what state is an "alarm". It monitors all
circuits, and informs the operator when any
circuit goes into alarm. Simply called SCADA.
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Mimic board
Breaker Mechanism
Analog meters
VT
CT
Transducer
Protective relay
RTU
Station computer
Central control (SCADA)
Monitoring Control of local system using
RTU Automatic functions for local control
performed by regulators, as well as sequence
control performed by relays are integrated as
software functions in the RTU.
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One of key processes of SCADA is the ability to
monitor an entire system in real time (run with
relatively little human intervention). This is
facilitated by data acquisitions including meter
reading, checking statuses of sensors, etc. The
SCADA software is a graphical package using a
Window NT Operation System.  The system,
manufactured by Power Measurement Ltd (PML),
provides the programming necessary to incorporate
actual AutoCAD campus maps and diagrams, and to
display real time information on top of the
graphic background.
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TECHNICAL FUNCTIONS OF SCADA The SCADA system
provides the following functions Data
acquisition The basic information of the power
system collected is called the Data Acquisition.
The data is collected by means of CTs, PTs and
transducers. It provides the telemetry
measurement and status indication to the
operator. Supervisory control It enables the
operator to remotely control the devices. For
example open and close of the circuit
breaker. Tagging It prevents the device from
unauthorized operation. Means it authorizes the
device to perform the specific operation. Alarms
It informs the operator about the unnecessary
events and undesired conditions. Logging
(Recording) It logs all the operating entry, all
alarms and other information. In other words it
keeps the record of all the events. Load
shading It provides both the automatic and
manual control tripping of load during the
emergency. Trending It plots the measurement on
the selected time scale.
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ESSENTIAL FEATURES OF SCADA The simple layout of
the SCADA system with its essential features is
shown below in the fig
The SCADA system enables the operator to attain
the complete knowledge of the system in a single
room by means of display. Almost all the SCADA
systems are computer based (Digital computer).
This computer is located in the master unit. The
master unit is the heart of the SCADA system, it
comprises many of the i/p and o/p equipments to
receive and send the control message from and to
the RTU.
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All the data of operations of RTU are transmitted
to the master control unit and after collecting
the information the data are feed back to the
RTU. Also master unit consists of several modems
which are used to convert the digital into analog
or analog into digital message depending upon the
requirement. The received information of the
master unit is displayed on VDU and then is
printed for permanent record. In addition the
SCADA system also comprises some more peripheral
equipment such as control console, VDU, Alarms,
Printers, D/A converter and Recording
instruments. Visual Display Unit (VDU) replaces
mimic board to represent one line diagram,
tabular display, bar charts, curves and event
lists and used for entering commands to
system. Modern system includes the color display
which is used to distinguish b/w the different
voltage levels. Also different colors
differentiate the operator to understand the open
and close of CB, also the flashing indication can
be made which determines the change of the state
of any device. The audible alarms can be used to
alert the operator from the fault or condition.
The printers are used to have the permanent
records of the events. The D/A converter are used
to convert the digital information into the
analog information, and then the information is
supplied to the indicating or the recording
instruments. The recording instruments are used
to store the data of each remote station unit.
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FUNCTIONAL DIAGRAM OF SCADA The functional
diagram of SCADA consists of several parts such
as Data base, Data acquisition, Main machine
interface and application program etc, are shown
below in the fig
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• Data acquisition is the function of the SCADA
  which is required to perform the following
  functions
• It is used to read the power system data from
  100-250 RTU into the control center.
• It detects and handle the error conditions of RTU
  and communication link as well as.
• It can be used to check the limits such as
  high/low operating limit, thermal limits, and
  safe handling limits.
• It can be used to convert the analog data into
  the binary data.
• It stores only the error free data in the data
  b/c erroneous data causes the failure of program.
• It can interface with the data base manager,
  which generated the data address where data can
  be stored in data base.
• It completes all above tasks in less than 2
  seconds.
• Typically data acquisition is implemented by the
  master station, software, and computer. The
  software consists of hundreds of different
  programs at the same time these program needs
  access to describe the structure and state of the
  power system. Therefore the data base plays an
  important and central role in control system
  design. Thus the SCADA system requires an
  efficient and effective data base, data
  acquisition and main machine interface.

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• Data base as the name implies is base for all the
  functions (i.e. data acquisition, main machine
  interface and application program). The primary
  object of the data base is to provide a well
  defined processing for several functions. Data
  base is repertory for all power system dynamic
  data, common data, user program and manually
  entered variables from operator console and
  network data such as historical files and record
  of data. It physically resides within the
  computer system. The data base in the SCADA
  system provides the following advantages
• It provides organized structure of data expressed
  in file.
• It stores the data with very little space
  require. Also it provides the flexibility in the
  selection of storage medium.
• It provides the discrimination b/w data and
  program or b/w two programs.
• It provides a well defined expansion of software
  system.
• A SCADA system includes a user interface, usually
  called Human Machine Interface (HMI). The HMI of
  a SCADA system is where data is processed and
  presented to be viewed and monitored by a human
  operator. This interface usually includes
  controls where the individual can interface with
  the SCADA system.
• Usually RTU's or PLC's will run a pre programmed
  process, but monitoring each of them individually
  can be difficult, because they are spread out
  over the system, HMI's are an easy way to
  standardize the facilitation of monitoring
  multiple RTU's or PLC's (programmable logic
  controllers).
• HMI's can also be linked to a database, which can
  use data gathered from PLC's or RTU's to provide
  graphs on trends, logistic info, schematics for a
  specific sensor or machine or even make
  troubleshooting guides accessible.

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PERFORMANCE MONITORING The performance
monitoring is used to enhance the operations
availability of SCADA or control center systems.
The basis requirement for the control center is
the availability of the SCADA and its
communication systems as well as RTU. All of
these equipments must be greater than the rated
capacity of the power system network. The power
system must remains in the operation even at the
time of the electrical faults, mechanical
failure, and other environmental conditions. The
basic philosophy of performance monitoring is
that if any single fault occurs with the SCADA
system, then the SCADA system should be able to
withstand against that fault and operates without
any disturbance. For that purpose several
facilities such as fail over equipments, backup
hardware and device are provided with the
computer to bypass the faulty program in order to
recover the operational status of the SCADA
system. The availability is increased by the
equipments redundancy. The software availability
is increased by including the error detection,
error handling, and fail over recovery and
automatic restart facility. The performance
monitoring nowadays is used in all SCADA ad other
control centers b/c it provides the whole
software availability and control of hardware.
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OPERATING SYSTEM The operating system is
required to provide a real time priority and
oriented process environment for computer. The
operating system provides the following
facilities Multi-computing, multi-programming
environment for program execution. Also
multi-processor are desirable for availability
point of view. (ii) Timer facilities. (iii)
Interrupt handling (iv) Error detection and error
handling (v) Input and output handling (vi)
Recovery and automatic restart facility (vii) On
line file management (viii) Language processor
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LAYOUT OF VDU DISPLAY The VDU display is used
in SCADA to observe different states of the
system. It enables the operator to find out the
desired information in fast manner. The VDU
display consists of two kinds of information
(i.e. General information and specific
information). The general information as the name
implies is generally used for all display and is
thus always shown on the screen. The specific
information is used to any specified device, it
is only used when is desired. The general
information will of course different for
different systems. But the most general layout of
the VDU display is shown below in the fig
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• The display identification normally shows
  substation name and type of information.
• Page no block shows the page numbers, if the
  pages are more than one then X (Y) form is used.
• System block shows the present part of the system
  on which the operator is working.
• Actual time block indicates the time of day.
• The latest unacknowledged alarm block shows the
  alarm alert situation.
• Dynamic functional keys comprises several keys,
  each key has got its own work such as display
  paging and object selection etc.
• The dialog field indicates the error message to
  the operator or it contains any other message
  entered from the operator
• PRESENTATION (CRT DISPLAY)
• The CRT stands for Cathode Ray Tube is available
  in the control room it provides the information
  about the i/p quantities to the operator. The
  information about any equipment can be displayed
  from the screen by simply pressing the button on
  the control desk. CRT display is located in
  control room of generation station, sub-stations
  and control center. The CRT display includes
• Alpha-numeric Displays These displays show the
  reading and name of the measured parameter.
• Single Parameter Displays These displays show
  the numerical data for certain parameter in
  tabular form.

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Mimic Displays These display show the single
line diagram of CB, Isolator and power flow in
the network. Display with threshold blackout
These displays show the threshold values of the
quantity. Threshold means on the
border. Graphical Display These displays show
the graph of quantities. Histogram Display These
displays show the graphical representation of a
distribution of quantity. Pictorial Displays
These displays can be used as small mimic
display. It shows the line diagram of a plant
indicating positions of equipments. Analogue
Displays These displays show the continuously
varying parameters. Alarm Displays These
displays show the control board for the attention
of the operator. OPERATING SYSTEM The operating
system is required to provide a real time
priority and oriented process environment for
computer. The operating system provides the
following facilities (i) Multi-computing,
multi-programming environment for program
execution. Also multi-processor are desirable for
availability point of view. (ii) Timer
facilities. (iii) Interrupt handling (iv) Error
detection and error handling (v) Input and output
handling (vi) Recovery and automatic restart
facility (vii) On line file management (viii)
Language processor
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• KEYBOARD DESIGN
• The keyboard is the device by which the operator
  enters the command to the computer. The keyboard
  contains the following keys
• Keys for display and substation selection
• Subsystems and Stations
• One lines, tabular display, event display, curves
  etc
• Function menu
• Keys for function selection
• Control
• Regulation (Raise/Lower)
• Data entry and Cancel
• Keys for function execution
• Close/Start and Open/Stop
• Select
• End of entry
• Keys for console assignment
• - Primary/Backup
• - Multi VDU selection
• Real time/Training/Study
• Dynamic keys

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MAIN TASKS IN POWER SYSTEM OPERATION The main
tasks of power system can be divided into the
following categories 1. Planning
operations 2. Operation control 3. Operating
accounting and financial control The above tasks
are performed by the National control center,
Regional control center, District control center
and Major substation control rooms. 1) Planning
of operations Planning means the formulating and
preparing actions before put into the use.
Planning is done for next hour, next day, next
week, next month, and next year and for long
range. Planning tasks includes ? The national
load center performs the following tasks First
of all load prediction followed by generator
scheduling, spinning reserves, planning of
reserves, planning of maintenance schedules,
planning of energy resource, selection of energy
resource, hydro-thermal generation co-ordination,
planning of power exchange b/w two regions and
planning of installation of HVDC lines. ? The
Regional load center performs the following
tasks First of all load prediction followed by
generator scheduling, planning of reserves,
planning of maintenance schedules and selection
of load scheduling. ? The District load center
performs the following tasks First of all short
term planning in terms of regional level planning
and then followed by planning of generation and
reserves, and planning of load shedding in
district. ? The Power station and sub-station
control room performs the following tasks Work
planning for hourly, daily, weekly, monthly.
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2) Operational control tasks An electric supply
corporation basically must meet the following
aims -There must be continuity of the power
supply for the consumer. -The network will be
designed in such a manner so as to cover the
---maximum consumers. -Maximum security of
supply -Less possibility of the fault -Maximum
efficiency of the plant -Consistency of the
frequency -Consistency of the voltage -Supply
power at low cost The national load center
performs the following tasks -Accuracy of
generation, and load and frequency -Power
exchange under emergency case -System frequency
control The Regional load center performs the
following tasks -Accuracy of generation, load
and frequency and power exchange b/w districts
under emergency. The District load center
performs the following tasks -Accuracy and
control of generation in district -Control of
power station -Control of T/L and tie-lines
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The power station and sub-station control room
performs the following tasks -Generation, start,
stop function -Automatic restoration
function -Control and protection
functions Maintenance The transmission
sub-station performs the following
tasks -Switching operation -Protective
functions -Voltage control and reactive power
compensation -Data collection -Load shedding
instructions. 3) Operating accounting and
financial control The operating accounting deals
with the data collection and evaluation and then
preparation of the financial reports and
billings. The task includes first of all the data
collection regarding the power produced, and then
billing on that power interchange for adjacent
station, then estimate the performance of the
power station, then estimate the price of the
power available for the consumer.
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Control Components of an Industrial Control
System (ICS)
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• The key control components of an ICS, including
  the control loop, the HMI, and remote diagnostics
  and maintenance utilities, are shown in Figure .
• A control loop consists of sensors for
  measurement, control hardware, process actuators,
  and communication of measurement variables.
  Measurement variables are transmitted to the
  controller from the process sensors. The
  controller interprets the signals and generates
  corresponding control signals that it transmits
  to the process actuators. Process changes result
  in new sensor signals, identifying the state of
  the process, to again be transmitted to the
  controller.
• The HMI allows a control engineer or operator to
  configure set points, control algorithms and
  parameters in the controller. The HMI also
  provides displays of process status information,
  including alarms and other means of notifying the
  operator of malfunctions. Diagnostic and
  maintenance tools often made available via modem
  and Internet enabled interfaces, allow control
  engineers, operators and vendors to monitor and
  change controller, actuator, and sensor
  properties from remote locations.
• A typical industrial system contains a large
  number of control loops, HMIs and remote
  diagnostics and maintenance tools built on an
  array of network protocols. Supervisory level
  loops and lower level loops operate continuously
  over the duration of a process at cycle times
  ranging on the order of milliseconds to minutes.

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SOME VIEWS ABOUT SCADA
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Following Figure provides a generic SCADA Network
Architecture that provides for an electric power
example and an oil gas/water example.
See description in Annex. A
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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.
View of Mimic diagrams
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Annex. A

• Application Server A computer responsible for
  hosting applications to user workstations.
• Backup Domain Controller Backup to the Primary
  Domain Controller.
• Control Server A server hosts the supervisory
  control system, typically a
• commercially available application for DCS or
  SCADA systems, and communicates data
• between the Peer-to-Peer network and the LAN.
• Data A repository of information that usually
  holds plant wide information including process
  data, recipes, personnel data and financial data.
• Distributed Control System (DCS) A supervisory
  control system typically controls
• and monitors set points to sub-controllers
  distributed geographically throughout a factory.
• Distributed Plant A geographically distributed
  factory that is accessible through the Internet
  by an enterprise.
• Domain Controller - A Windows NT server
  responsible for managing domain information, such
  as login IDs and passwords.
• Enterprise A business venture or company that
  encompasses one or more factories.
• Enterprise Resource Planning (ERP) System A
  system that integrates enterprise-wide
  information including human resources,
  financials, manufacturing, and distribution as
  well as connect the organization to its customers
  and suppliers.
• Fieldbus - A category of network that links
  sensors and other devices to a PC or PLC based
  controller. Use of fieldbus technologies
  eliminates the need of point-to-point wiring
  between the controller and each device. A
  protocol is used to define messages over the
  fieldbus network with each message identifying a
  particular sensor on the network.

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Firewall A device on a communications network
that can be programmed to filter information
based on the information content, source or
destination. Human Machine Interface (HMI) The
hardware or software through which an operator
interacts with a controller. An HMI can range
from a physical control panel with buttons and
indicator lights to an industrial PC with a color
graphics display running dedicated HMI
software. Internet a system of linked networks
that are worldwide in scope and facilitate data
communication services. The Internet is currently
a communications highway for millions of
users. Input/Output (I/O) Module relaying
information sent to the processor from connected
devices (input) and to the connected devices from
the processor (output). Light Tower A device
containing series of indicator lights and an
embedded controller used to indicate the state of
a process based on an input signal. Local Area
Network (LAN) A network of computers that span
a relatively small space. Each computer on the
network is called a node, has its own hardware
and runs its own programs, but can also access
any other data or devices connected to the
LAN. Printers, modems and other devices can also
be separate nodes on a LAN. Modem A device that
allows a computer to communicate through a phone
line. Management Information System (MIS) A
software system for accessing data from
production resources and procedures required to
collect, process, and distribute data for use in
decision making. Manufacturing Execution System
(MES) Systems that use network computing to
automate production control and process
automation. By downloading recipes and work
schedules and uploading production results, a MES
bridges the gap between business and plant- floor
or process-control systems.
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OPC Client/Server Mechanism for providing
interoperability between disparate field devices,
automation/control, and business
systems. Peer-to-Peer network A networking
configuration where there is no server and
computers connect with each other to share data.
Each computer acts as both a client (information
requestor) and a server (information
provider). Pressure Sensor A sensor system that
produces an electrical signal related to the
pressure acting on it by its surrounding
medium. Primary Domain Controller A Windows NT
server responsible for managing domain
information, such as login IDs and
passwords. Printer A device which converts
digital data to human readable text on a paper
medium. Proximity Sensor A non-contact sensor
with the ability to detect the presence of a
target, within a specified range. Redundant
Control Server A backup to the control server
that maintains the current state of the control
server at all times. Remote Terminal Unit (RTU)
A computer with radio interfacing used in remote
situations where communications via wire is
unavailable. RTUs are usually used to communicate
with remote field equipment. PLCs with radio
communication capabilities are also used in place
of RTUs.
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Sensor - A device that senses or detects the
value of a process variable and generates a
signal related to the value. Additional
transmitting hardware is required to convert the
basic sensor signal to a standard transmission
signal. Sensor is defined as the complete sensing
and transmitting device. Supervisory Control and
Data Acquisition System (SCADA) Similar to
a Distributed Control System with the exception
of sub-control systems being geographically
dispersed over large areas and accessed using
Remote Terminal Servers. Temperature Sensor A
sensor system that produces an electrical signal
related to its temperature and, as a consequence,
senses the temperature of its surrounding
medium. Workstation A computer used for tasks
such as programming, engineering, and
design. Wide Area Network A network that spans
a larger area than a LAN. It consists of two or
more LANs connected to each other via telephone
lines or some other means of connection. Wireless
Device A device that can connect to a
manufacturing system via radio or infrared waves
to typically collect/monitor data, and also in
cases to modify control set points.