Scada Saif

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    Prerequisite

    Bit is binary representation 0 or 1.

    One byte contains 8 bits.

    Baud rate is used to express totalcapacity of communication channel.

    Bandwidth is the frequency range of

    channel.

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    Modulation

    The process of superimposing lowfrequency signal on a high frequency

    carrier is called modulation.

    Demodulation

    Extraction of base band signal fromhigh frequency carrier.

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    Transmission

    Synchronous & Asynchronous

    Synchronous transmission

    The transmission is started with startbit and continuous the transmissionends with a stop bit.

    Asynchronous transmission deals inform of frame including start andstop bit total 10 bits.

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    Communication Channel

    Half Duplex

    Full Duplex

    Half duplex channel can send andreceive but not at the same time.

    Full duplex channel can send andreceive at the same time.

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    Switching techniques

    Circuit Switching

    Dedicated communications pathestablished for the duration of theconversation

    e.g. telephone network

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    Packet Switching

    Data sent out of sequence

    Small chunks (packets) of data at a

    time Packets passed from node to node

    between source and destination

    Used for terminal to computer andcomputer to computercommunications.

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    SCADA

    Supervisory Control And DataAcquisition.

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    Communication Media

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    Satellite Communication

    Equipment

    RFT

    Modem

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    Remote Terminal Unit

    Communication with control centre.

    Acquisition of status signal.

    Sequential event recording. Remote diagnostic facilities.

    Connection of subordinate terminals.

    Print out of events. Review

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    Collector 400

    Remote Terminal Unit.

    Local data acquisition and dataprocessing.

    Reporting and control.

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    Control Commands

    Two types of commands

    Item Control commands are normallycarried out using two step procedure.

    Examples are circuit breaker anddisconnectors.

    Regulation command are carried out

    single step procedure. Example ofregulated equipment and tapchangers on transformers.

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    Function in collector 400

    It uses local input output systemwith analog input board, digital

    output boards, energy pulsecounter, command board, digitaland analog output boards.

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    Standard Additional Functions.

    Permanent Connection.

    Reconnectible.

    Radio link equipment. Local alarm with communication

    failure.

    Both half and full duplexcommunication.

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    Modular system assembly

    Contains back plane for 19 racks.

    Plug in units for 19 racks.

    Base boards, processor boards andexpansion boards.

    Extension boards.

    Connection units.

    P I t f S t

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    Process Interface System

    The DS100l0 system includes units forinterfacing between computer and theprocess i.e.

    Digital input and output boards.

    Analog input and output boards.

    The signals are converted in interface

    board for transmission as A/D, D/Aconversion. Filtering, rectificationamplification.

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    Single board computer

    It is provided with V24 channels forconsole communication.

    DSPC 155 is designed around 32 bitinternal structure 4 MB of internalmemory and 4 MB virtual memory. Eprom of 320 KB. Internal memory of

    512 KB.

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    Memory board DSMB 110

    The board contains high capacity 128KB dynamic read / write memory.

    The board functions as asynchronousstatic memory.

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    Communication board with line

    selector DSCA 140

    Three communication ports with V24.

    Port is selected on board logic.

    Synchronous communication can beused.

    Programmable baud rate.

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    What is multiplexing.

    Different kind of data transmittedover single line.

    Example is voice, data, fax, etc.

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    Floppy disk unit DSMC 110

    It can control two floppy units ofBASF 6108 type or similar with 5.2

    Voltage required by floppy disk unitsare provided by the DSMC 110.Theunit is equipped with a 256 bytessector buffer for reading and writing.

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    Pulse counter Board

    Board is galvanically isolated by otherparts by mean of opt couplers.

    There are other digital and analoginput output boards with differentspecifications.

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    CTU

    Collector test unit is a test unit forRTU.

    CTU is software loaded in PersonalComputer.

    Almost all controlling is made with 8dynamic function keys(F1-F8).

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    Multiplexer

    30 user channels of 64K bandwidthcan

    be combined into an E-1 circuit.

    E1- Mux

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    Cards used in mux

    V.35 is used for data.

    LGS is used for voice.

    Dsp is application card for voicecompression.

    E1 is basic channel communication

    card.

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    Where Mux is needed ?

    Mux is not generally used in applicationswhere a client simply has a leased line andwants to send only data traffic. In this

    case they would simply use two DTUs(Data Termination Unit) at their twopremises to extend the digital connection.

    Also mux can be used when the wan

    connectivity is not through leased line butradio modems or satellite modems.

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    Modulation using FSK modem.

    Values represented by different values.

    Less susceptible to errors.

    Up to 1200bps on voice grade lines.

    High frequency radio. (3 to 30 MHZ)