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    1.0 INTRODUCTION

    SCADA stands for supervisory control and data acquisition. It generally refers to

    industrial control systems: computer systems that monitor and control industrial,

    infrastructure, or facility-based processes, as described below:

    Industrial processes include those of manufacturing, production, powergeneration, fabrication, and refining, and may run in continuous, batch, repetitive,

    or discrete modes.

    Infrastructure processes may be public or private, and include water treatment

    and distribution, wastewater collection and treatment, oil and gas pipelines,

    electrical power transmission and distribution, Wind farms, civil defense siren

    systems, and large communication systems.

    Facility processes occur both in public facilities and private ones, including

    buildings, airports, ships, and space stations. They monitor and control HVAC,access, and energy consumption.

    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 andsending 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 aremore economical, versatile, flexible, and configurable than special-purpose RTUs.

    Communication infrastructure connecting the supervisory system to the RemoteTerminal Units.

    Industrial Use of SCADA System

    This article describes the function of SCADA, its application in oil and gas

    flowing, waste water management, power and electricity surges.

    WHAT IS SCADA AND ITS NEED?SUPERVISORY CONTROL AND DATA ACQUISITION

    We more frequently call it as SCADA. As the name implies SCADA system

    supervises, acquires and control data received from a distant data source from the

    control center. SCADA system is located in the control center and is operated in

    the scanning mode, communicating between the CONTROL CENTER and the

    REMOTE STATION by means of two-way communication channels. Such a

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    supervisory control and data acquisition system is intended to facilitate the work of

    operator by acquiring and compiling information as well as locating, identifying

    and reporting faults. On the basis of information received, the operator makes

    necessary decisions via the control system he can then perform different control

    operations in power stations or influence the processing of the information

    acquired. The main task of a modern day power system is to ensure quality and

    reliable power at an economic rate. Hence the system is to be updated at a very fast

    rate (real time

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    Mode/management), which helps to control the complex system effectively

    without any loss of time.

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    A BRIEF HISTORICAL PERSPECTIVE

    Telemetry systems were initially developed in the 1960s for remote monitoring and

    control of geographically distributed critical infrastructure such as railroads; gas

    and liquid pipelines; electric power transmission and distribution systems; andwater/wastewater systems. Prior to the introduction of supervisory control and data

    acquisition (SCADA) technology these facilities used a variety of telemetry

    schemes, the most popular of which was frequency division multiplexing (FDM or

    Tone) telemetry. Telemetry has always involved electrical and electronicequipment, but prior to 1970, these were primarily hardwired architectures using

    relatively simplistic communications schemes.

    SCADA systems are based on the use of a central computer to communicate with

    remote data acquisition and control equipment. A significant reason for the growth

    and proliferation of SCADA technology in the 1960s and early 1970s was the

    introduction of lower-cost computing platforms (i.e., 8- and 16-bit minicomputers)

    during that same period. SCADA systems prior to the development of

    minicomputers were built around large, expensive mainframe computers. As such,

    they were relegated to only the most critical applications that could justify the

    substantial expense. Electric utilities were among the first to make significant

    investments in modern SCADA technology.

    2.0 SCADA FUNDAMENTALS

    With the advent of lower cost computer technology it became possible to usecomputers, and appropriate software, to perform the functions previously relegated

    to the panel instruments and tone telemetry, and in particularly the electronic head-

    end display technology. Computers could be programmed to communicate with

    newly developed electronic field data acquisition and control units in the same

    manner used by the earlier hardwired master station equipment.

    2.1 Supervisory Control And Data Acquisition (SCADA) Systems

    All supervisory control and data acquisition (SCADA) systems have several basic

    components: a central computer (probably redundant), a human-machine interface,

    electronic field terminal units (usually called RTUs) and some type ofcommunication infrastructure to connect the central computer with the field data

    acquisition and control units. SCADA systems have evolved over time and have

    architecturally followed the changes in computer and communications technology.

    One of the primary technology drivers that pushed the development of SCADA

    technology was the development of low-cost 8- and 16-bit computers called

    minicomputers, the other being the development of the microprocessor several

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    years later. The microprocessor advanced remote terminal unit (RTU) technology

    in the 1970s in much the same way that minicomputers advanced the technology of

    SCADA master stations in the 1960s.

    Prior to the arrival of microprocessors, RTU equipment was hardwired for a

    specific set of functions, a fixed quantity of I/O and a fixed-format digitalmessaging scheme. In the 1970s RTUs based on microprocessor technology were

    introduced. These new intelligent RTUs could be programmed to perform newand more sophisticated functions, and could even be modified by the end user.

    SCADA systems have steadily benefited by incorporating in advances in computer

    technology throughout the past three decades.

    SCADA systems are used to monitor and control geographically distributed

    processes. This means that they allow the user of such a system to see what ishappening at the geographically distant locations and to effect a certain level of

    control over the equipment/process at those locations.

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    2.2 SCADA Master Station (Host) Computer Systems

    The SCADA Host (orMaster Station) computer is the repository of the real-time

    data that is collected from all of the various RTUs connected to it in any form.

    Architecturally,Hostcomputer configurations have evolved through the years and

    have done so because of changes in computer technology. Very few SCADAsystem suppliers have actually designed and built their own computer equipment.

    Although a couple of computer manufacturers (notably IBM and CDC) developed

    relatively short-lived SCADA systems, most are compelled to create mission-

    critical SCADA systems using commercial off-the-shelf (COTS) computing

    technology.

    The SCADA host must have software to continuously send polling messages to all

    of the RTUs, using the designated protocol, and must also be able to retrieve,

    process and store the information returned from the various RTUs. This generally

    means that there is some form of table internal to the host that contains the mostrecent values from all of the RTUs. In many cases, this RTU data may be in raw

    counts and must therefore be converted to relevant engineering units by the host.

    This also means that a set of numeric values (the m and b quantities in the

    equation y=mx+b) associated with each incoming data value, which define the

    linear conversion calculation must also be accessible. Finally, there needs to be a

    way to reference each incoming value. Referring to a signal as the twelfth analog

    input from the RTU with address 4 on the 6th

    polling channel, though rather

    clumsy for practical use, is actually how the computer finds that particular value.

    Thus, all SCADA systems feature some sort of naming scheme whereby a tagname (e.g., LAK-T202-TTT) can be associated with each input and output.

    2.3 Remote Terminal Units (RTUs)

    An RTU is an electronic device that has special circuitry allowing it to interface

    with process instrumentation and control equipment. Physical parameters such as

    pressure, flow, temperature, etc. are measured by special sensory devices that

    generate an electrical signal corresponding to the parameter value. Some

    measurements only have two values or states (such as is a motor on or off, is a

    valve open or closed, etc.) These can be electrically represented with a simple

    contact (switch) signal. The RTU has electronic input and output circuitry thatpermits the RTU to measure and generate these electrical and contact signals.This is generally referred to as I/O (input/output) circuitry.

    There are two categories of such I/O hardware: analog and digital. Analogcorresponds to measurements that have a numeric range (e.g.50 to 200 C)

    represented by a voltage signal over a corresponding range (e.g.10 volts to +10volts.) The I/O section of the RTU uses a circuit called an analog-to-digital

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    converter (ADC) to generate a numeric value from the voltage input signal.

    Digital corresponds to measurements that have a limited number of states (most

    often two) that can be represented by the state of a contact. This I/O section uses

    circuitry to sense the state of the contact and generates a binary flag that

    corresponds to the state.

    Since the RTU (at least today) is a microprocessor-based device, such values and

    measurements are represented internally (within the microprocessor of the RTU) as

    binary numbers or discrete bits. Usually an ADC generates a fixed sized binary

    value (12, 14 and 16 bit values are typical.) In a similar manner, the output portion

    of the I/O circuitry allows the RTU to generate a voltage signal or a contact signal

    that can be used to control process equipment (such as starting a motor or adjusting

    the position of a valve.)

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    The basic job of the RTU is to scan through all of the signals wired to its inputs

    and record their values, and then to repeat this process over and over again so that

    it always has the current values. These values can then be sent to the SCADA

    central computer and presented to the human that is monitoring the process. In a

    basic RTU these values will be represented as raw counts and binary flag bits.Therefore, a field measurement value of -20C to 150C might be represented by a

    binary count in a numeric range of 0000 to 8191 (01FFF hexadecimal, a 12 bit

    value). Obviously, these raw counts need to be converted into the proper

    measurement value (typically called the engineering units value) beforepresentation to a human operator. In a SCADA system this can be done either

    within the RTU, or at the central computer, depending on the capabilities of the

    RTU.

    The original non-microprocessor-based RTUs had no arithmetic or computational

    capability and so they only provided raw count values. Thus, all early SCADAsystems did the conversion to engineering units in the central computer (and the

    communication scheme and message formats used, were based on transmission of

    raw count values.) More recently, based on microprocessor-based RTU

    technology, there have been systems where value conversion (and even alarm

    checking) has been accomplished within the RTU.

    One reason for this has been the implementation of control and calculation logic

    within the RTU, and even local operator displays, and thus the need for

    engineering units. In a much simpler manner, binary/status inputs also can beconverted to engineering units. This involves providing a text description for the

    binary states. Thus, rather than indicating the status of a pump as 1 you wouldsubstitute the text string RUNNING. In the same manner you would provide

    STOPPED rather than 0 for the alternate state. This evolutionary step, of doing

    value conversion within the RTU, has been most prevalent in the pipeline industry

    and somewhat less in the water/waste-water industry. It has not been a technology

    trend in the electric utility industry.

    2.4 RTU Technology Advancements

    As RTUs became smart through the application of microprocessor technology,

    they began to provide a platform for adding increasing functionality. Because they

    could be (re)programmed it was possible to make continuous enhancements (orcorrect bugs) simply by changing the programming. As new functions wereadded, the digital communications messaging scheme (commonly called a

    protocol) could also be modified to support these new functions and features.

    Of course, this also made it more difficult to maintain compatibility with SCADA

    systems and product families. But, the new features and functions were compelling

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    and so vendors and customers put up with the problems. Every SCADA vendor

    was originally in the business of building their own, proprietary RTUs, and

    inventing their own communication protocols. Eventually (in the mid to late

    1990s) a few protocols became dominant and de facto standards to which most

    vendors eventually conformed. These de facto standards vary by industry segment

    and in some cases dont support all/any of the more advanced functions typically

    supported by a given vendors proprietary protocol (e.g., it may be possible toconfigure and download new RTU software using the vendors proprietary

    protocol, but not using a standard protocol.)

    As previously mentioned, the basic function of an RTU is to scan and process

    inputs and provide them to the SCADA central computer (also called the host)when requested, using a digital communication messaging scheme (a protocol.)The second part of this base functionality is the ability of the host to send protocol

    messages to the RTU that cause it to manipulate its output

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    values. This may mean adjusting a voltage output that is controlling a pumpsspeed, or closing a contact that stops a motor. In a basic RTU the outputs are

    ONLY manipulated at the request of (receiving the correct messages from) the host

    computer. These two components: scanning inputs and manipulating outputs,

    comprise the basic aspects of supervisory control.2.5 SCADA Communications

    The RTU needs to be able to send its data to the host computer for presentation to

    the user of the SCADA system, and needs to receive control command messages.

    This means that there has to be some form of communications system to transport

    the protocol messages between the host and the various RTUs. Since, by nature,

    SCADA systems tend to encompass a large geography with RTUs situated

    throughout the area, the communications technology employed must embrace this

    architecture. Moreover, there are industry- and application-specific speed and

    performance requirements related to the particular process dynamics of eachmarket.

    Another key consideration is the availability (or sometimes, the unavailability) of

    suitable commercial/public communications infrastructure. All of this must be

    taken into account in designing a SCADA communications scheme.

    Prior to the development of computer networking the vast majority of

    communications technologies for communicating over great distances, to a large

    number of locations, were designed for voice communications among human

    beings. These included radio, telephone, microwave and even satellite

    communications systems. It is important to remember that the telephonecompany (Ma Bell) pioneered microwave, satellite, fiber-optic and cellulartelephone technologies as a means for providing voice telephone service.

    By making use of this voice-based technology, SCADA systems were implicitly

    restricted to the bandwidth limitations of such systems. Since a voice circuit carries

    sound, the digital information being transmitted between RTUs and SCADA hosts

    had to be converted into audio signals to make use of the then-available

    communications networks. That meant the use of special circuitry to modulate and

    de-modulate (a modem) the digital signal.

    Early modems supported rather low data rates: 1200 and 2400 bits per second. This

    limited data rate caused RTU/SCADA vendors to design their protocols to be as

    efficient (and feature-poor) as possible, so that polling of an RTU would take as

    little time as possible. Some of these communications schemes could be used in a

    multi-drop or point-to-point configuration; others (e.g., radio) only in a multi-drop

    arrangement.

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    When a radio enabled SCADA host transmits a message on frequency X all ofthe RTUs hear it because they are all listening on frequency X. Only one RTU

    can answer at a time or they will interfere with each other (like multiple students

    answering the teachers question at the same time.) Thus, the host has to

    interrogate each RTU in turn in order to collect all of their information. Adding

    more RTUs extends the cycle time for each polling sequence. With a telephone

    system, it would be possible (although more expensive) to have a separate phone

    circuit to each RTU so that the host could communicate with multiple, or all, RTUs

    concurrently.

    A less costly alternative might to allow a few RTUs to be multi-dropped on each

    circuit, thus minimizing the polling cycle time. With all RTU protocols that

    support multi-dropping there is a method for identifying the particular RTU to

    which the host message is directed. This is usually in the form of a unique number

    or address that is part of the message. All RTUs on a shared (multi-dropped)

    circuit hear the host messages, but only the RTU with a matching address numberwill respond to a given message. GITA CONFERENCE PROCEEDINGS Sunday,

    April 23, 2006 (Tampa, Florida) ShawW.doc Page 6 of 10 6/8/2006

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    In practice, the electric utility market has tended to use a dedicated leased

    telephone circuit to each RTU, or have constructed their own telephone

    infrastructure (using the same technology as the telephone company) to provide a

    separate circuit to each RTU. This has allowed host data updates every 1 to 5

    seconds, from ALL field sites, even at low data rates such as 1200/2400 bits persecond. Why would an electric utility choose to construct its own telephone

    infrastructure? In many cases because their long-haul transmission systems were

    out in wide-open areas where there was no telephone service. So they built their

    own.

    Another type of electric utility is the municipal electric utility, typically having a

    more limited geographical service area than IOUs. These utilities have used leased

    telephone circuits extensively and have recently begun creating their own fiber-

    optic communications systems. Since much of a municipal electric utilitys servicemission is power distribution, there has also been widespread use of radio

    communications for SCADA systems implemented for distribution automation and

    distribution management purposes.

    By contrast, many water/wastewater utilities have elected to use radio-based

    communications systems for their SCADA applications. This is possible because in

    most cases, the utility service area was large but geographically restricted to an

    urban area, all within the distance limits of conventional radio (possibly with a few

    repeaters). Also, this was often part of a system that the utility already owned and

    operated for voice communications or other purposes.

    Radio-based polling is generally a multi-dropped scheme, causing polling cycles

    might require several minutes to complete. However, the process dynamics ofwater/wastewater systems are relatively slow and can tolerate fairly long periods

    between host data updates of all but the most critical information. Many such

    systems have been deployed using leased telephone circuits, but unlike electric

    utilities, often with multiple RTUs per circuit. Some utilities have a mixture of

    radios and leased circuits, sometimes with one as a backup to the other (e.g.,

    switch to radio, and accept a performance reduction, if the telephone lines go

    down.)

    Pipeline applications, like electric power transmission systems, often require

    communications over very long distances and extending into remote locationswhere no telecommunications infrastructure exists. Historically, pipeline

    companies have generally constructed their own communications systems, initially

    using microwave backbones and more recently switching to fiber-optic cables.

    In the 1980s and 1990s, several pipeline SCADA systems made use of commercial

    satellite technology and something called X.25 packet switching technology, which

    pre-dates modern digital networking. In general most older pipeline SCADA

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    systems have tended to be designed with a goal of full host data updates from all

    RTU sites every 10 to 30 seconds.

    Until fairly recently, when SCADA deployment involved building a private

    telecommunications infrastructure, it was based on voice telephone technology and

    thus often provided many more voice circuits than were needed for the SCADAproject. (In many cases, this excess circuit capacity was leased back to the local

    telephone company to help underwrite some of the project expense.)

    3.0 SCADA FUNCTIONALITY

    A SCADA system might be continuously fetching and processing hundreds to

    thousands of values, every polling cycle. There is no practical way for a human to

    look at all of these values to see if they are within acceptable/expected bounds.

    DATA ACQUSITION- Furnishes status information & measurands data to

    operator

    CONTROL - Allows the operator to control the devices e.g. ckt breakers, Xmer,

    tap changer etc from a remote centralized location .

    DATA PROCESSING - Includes data quality & integrity check , limit check ,

    analog value processing etc.

    TAGGING - Operator identifies any specific device & subjects to specific

    operating restrictions to prevent from unauthorized operation

    ALARMS - Alerts the operator of unplanned events & undesirable operating

    conditions in the order their severity & criticalityLOGGING- Logs all operator entries, alarms &selected entries

    TRENDING- Plots measurements on selected scale to give information on the

    trends e.g. one minute, one hour etc.

    3.1 FUNCTIONAL UNITS OF SCADA:

    1. Data collection equipment.

    2. Data transmission / telemetric equipment.

    3. Remote terminal unit.4. Data loggers.

    5. Data presentation equipments.

    The figure shown below represents the simplest SCADA configuration employing

    single computer; Computer receives data from RTUs via the communication

    interface. Operators control base one or more CRT terminals for display. With

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    Fig. 1: Simple SCADA system with single computer

    terminal it is possible to execute supervisory control commands and request the

    display of data in alpha numerical formats arranged by geographical location and

    of type. The programming input/output is used for modifying the supervisory

    software. In the basic SCADA system, all the programs and the data is stored in the

    main memory. The more sophisticated version of SCADA has additional auxiliary

    memories in the form of magnetic disc units.

    As was mentioned, the purpose for doing alarm limit checking in the host was to

    identify measurements (or computed values) that were deviating in a suspicious ordangerous manner. Once identified, aside from setting a flag in the real time table,

    the SCADA system would bring the problem to the attention of the system user. In

    older systems this was accomplished by typing a message on a printer designated

    for alarming purposes. The system might also produce an audible alarm (to wake

    up a dozing system operator.)

    RTU RTU RTU

    C. P. U.Prog. I/O

    equipment

    Auxiliary Memory

    Communication

    Interface

    Display and

    Control

    Console

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    In most SCADA systems another important function is to provide a means for

    recording critical values over some time span back from the current time and date.

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    A very essential feature of most SCADA systems today is their ability to generate

    printed reports and logs. Hourly, shift, daily, weekly, monthly, quarterly and

    annual reports need to be printed on a routine, scheduled basis. Others need to be

    printed when specified trigger events take place.Older SCADA systems usually included a FORTRAN compiler that could be used

    for report programming. Today, with the ubiquitous presence of Microsoft

    software and spreadsheet tools, most SCADA systems offer those (with dll orodbc or plug-in connections to the real-time and historical data) for reportingpurposes.

    3.2 AUTOMATIC SUB-STATION CONTROLThe electrical energy is transferred from large generating stations to distant load

    centers via various sub-stations. In every sub-station certain supervision, controland protection functions are necessary. Every substation has a control room. The

    relay and protection panels and control panels are installed in the control room.

    The various circuit breakers, tap changers and other devices are controlled by

    corresponding control-relay panels. In a small independent sub-station, the

    supervision and operation for normal service can be carried out by the operator

    with the aid of analogue and digital control systems in the plant. The breakers can

    be operated by remote control from the control room. During faults and abnormal

    conditions, the breakers are operated by protective relays automatically. Thus, the

    primary control in sub-station is of two categories.1. Normal routine operation by operators command.

    2. Automatic operation by action of protective relays and control systems.

    3.3 SUB STATION CONTROL FUNCTION ARRANGED THROUGH

    SCADA SYSTEM

    1. Alarm FunctionsTo sound alarm/annunciation regarding dangerous, uncommon events such as

    abnormal values of process parameters, fire, illegal entry in premises, overtemperatures, low voltage of auxiliary supply, unusual happening etc. Alarms are

    obtained from data logger and are for alerting this operator in the control room.

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    2. Control and IndicationControl of two position devices such as, circuit -breakers, isolators, earthing-

    switches, starters. Indication of ON/OFF state of the devices on control

    board/mimic diagrams.

    Control of position of devices having positions (closed, middle open) e.g.

    values, input settings, indication of position on control panels.

    Control positions of multi-position device e.g. tap changer, indication of

    position on control panels.

    Indication without control.

    Control without indication: e.g. raise or lower control of generator load by

    automatic load frequency control.

    Set-point control to provide set point to a controller located at remote sub -

    station.

    3. Data collection, recording, display.

    4. Sequential operation of devices with predetermined time and conditions foroperation of various devicese.g.

    Auto-reclosing of circuit-breakers operation O-CO-Time-CO

    Operation of circuit-breaker, isolator and earthing-switch in a particular

    sequence during opening of circuit and another sequence during closing of circuit.

    5. By means of SCADA system, the operator in control centre can cause

    operations in a remote sub-station. The possible remote operations include:Opening and closing of switching devices I

    Tap-changing of transformers (voltage control)

    switching of capacitor banks (voltage control)

    Load shedding (load frequency control)

    6. Some of the remote operations are made automatic by one -line computer

    based system without human intervention e.g. Net work islanding, Backup

    protection. The automatic control function are segregated into :Interconnection functions

    Transmission line automatic function

    Distribution system automatic functions

    3.4 Advantages of SCADA system:1. Flexible, simple, reliable.

    2. Efficient with less manpower.

    3. Security.

    4. Self-checking and readability.

    5. Portable and cost efficient.

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    3.5 Applications of SCADA system:1. Inside power plant.

    2. On power plant.

    3. Industrial establishment.

    4. Load dispatch center.

    5. Railways.

    TWO-WAY COMMUNICATION CHANNELS BETWEEN THE MASTER

    CONTROL CENTRE AND REMOTE CONTROL CENTRE

    SCADA

    Traditionally, the SCADA systems were used for scanning mode, providing data

    regarding generating stations, generating units, transformer sub-stations etc.

    SCADA systems were arranged to perform several functions to supplementAutomatic Control and Protection Systems.

    Now a days protective relays, control relays and control systems are used for

    automatic control of generating stations and transmission systems along with

    SCADA. Only initiating devices may be different or omitted with fully automatic

    SCADA control. For example, tap changing may be initiated either by the sub-

    Station Check

    Trip-Close

    Lower-Raise

    Close-OpenStop-Start

    Analog DataCounted Data

    Binary Data

    Alarms & Status

    Indication

    M

    o

    d

    e

    m

    M

    o

    d

    e

    m

    Remote

    station

    Master

    Session

    Data Display

    Alarm

    Annunciation

    Indication

    Special

    Function

    A/D Converter

    Pulse Counter

    Binary Data

    Indication

    Analog Data

    ControlControl &

    Indication

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    section control room operator or by the automatic voltage control relays connected

    in the protection panel of the transformer.

    Controls systems were arranged to keep the values of controlled quantities within

    target limits. Protection equipments were arranged for sounding alarms and for

    tripping circuit -breakers.

    With the recent revolution in microprocessor technology, the size, performance

    and cost of digital automation systems have become acceptable in commercial

    installation. SCADA provides integrated approach to power system protection,

    operation control and monitoring, automatically with least intervention of the

    control room operator.

    The microprocessors located in the master station, generating stations, transmission

    sub - stations and distribution sub-stations provide control and protection decisions

    locally where the data is located. The action is reported to the operator "by

    exception". The operator retains the option of taking intervening action of

    overriding or initiating of his own. All these microprocessor based systems areconnected through the GLOBAL POSITIONING SYSTEM. The functions and

    architecture of SCADA system is selected in accordance with the functional

    requirements and size of the power system.

    4.0 FEATURES OF SCADA

    Tracker Option: This feature provides collection and storage of variety

    pertaining to the serialized items such as time stamps, quality measurements,

    temperature, humidity, pressure, sub- assembly part number etc through variousautomated sensors and readers like bar code readers, radio frequency tags, and

    mechanical tag based system. This information is used for over viewing the flow of

    serialized items and the location of materials through the system which helps in

    isolating the defective items from the perfect ones. For example boxes or

    containers over a specified weight limit may be routed to different storage area

    Data import/export function: This feature allows the transfer of all point

    configuration data via a comma separated variable file. Points are therepresentation of actual field parameters; these are the variables in which the actual

    incoming data is stored. Similarly point configuration can be sent to other SCADA

    system for their use over there. This is made possible through data import/exportfacility. Data management is possible using MS EXCEL,

    MS ACCESS etc.

    Flexibility: This feature provides tools by which an existing system could be

    tailored according to the changes taking place. Thus the user can mould the system

    according to the demands thus making it more flexible.

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    Forecasting: Forecasting is the ability to predict future state of the system by

    studying previously collected data. Forecasting feature of SCADA system allows

    the operator to visualize the state of the system well in advance, hence the operator

    has enough time to manage the system properly. This feature of SCADA finds a

    huge application in Energy Management System.

    Job Management: Using SCADA all the tasks can be properly sequenced and

    executed to allow the most efficient task scheduling for proper utilization of man

    and machinery of plant.

    4.1 SECURITY OF SYSTEM OFFERED BY SCADAIn the age of automated systems, security, reliability and availability of data is top

    priority of any computer based automated system. Small loss of data in such

    system can cause havoc and may bring a system to a standstill.

    SCADA ensures a high degree ofsecurity. Security of any process may be definedas the ability of the system to operate in normal state even with the occurrence of

    specified contingencies.

    The system shall by all means remain in the state of normal operation by means of

    fast acting control systems following a contingency and without having a system to

    go into an emergency state. Continuous monitoring of security and appropriate

    corrective action for improving security is called security control. System security

    analysis is generally broken down into following three functions:

    System monitoring: SCADA provides up to date information regarding the

    condition of the processes.

    Contingency analysis: Sometimes abnormalities give the operator very less time

    to react. SCADA system provides contingency analysis, which consists of action to

    be taken by the operator in advance. Thus it allows the system to operate

    defensively.

    Corrective action analysis: It allows the operator to take appropriate corrective

    action in the event of contingency in order to ensure the smooth functioning of the

    process.

    5.0 CONCLUSIONFrom the above paper we can summarize that the SCADA supplements the control

    and protection system to form an integrated system, which is compact, economical

    and versatile. In short we can say that it acts under the GLOBALPOSITIONING SYSTEM, so that whole system works in same time domain.

    Today the buzzword in any industry is Optimal Performance at MaximumEconomy.

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    SCADA has provided the industry with the perfect Man Machine Interfacewhich has solved many or to be precise, most of the problems related to

    monitoring, supervision, data acquisition and controlling. The most significant

    contribution of SCADA is probably having an easy -to-use graphical interface,

    which has made the tedious job of operators very easy. SCADA has manifold

    applications like Distribution Management, Energy Management, Power Plant

    Management & Oil and Gas Distribution System. SCADA has also enabled Grid

    monitoring by virtue of which power can by shared on national basis. So the

    bottom line is that SCADA is a boon to Indian powersector.

    REFERENCES1. Sunil S. Rao, Switchgear Protection and Power Systems

    2. A.K. Sawhney, Electrical Measurements & Measuring Instruments3. The Information Digest On EnergyVol -2 March1992.

    4. Tery News WireVolII Jan1996 - Dec1996.5. Tery Energy Environment Monitor- Vol-I March-1996.