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INDUSTRIAL AUTOMISATION PLC: Incorporation of PLC’s into the existing control systems M.V.S.PRAJITH 3/4 EEE(B.E) B.NAGARJUNA 3/4 EEE(B.E)

What is PLC? :

What is PLC? P rogrammable L ogic C ontroller

What does PLC do?:

What does PLC do? A PLC is an industrial computer control system used for automation of real-world processes,usually uses a microprocessor that continuously monitors the state of input devices and makes decisions based upon a custom program.

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PLC SYSTEM Input Section 2. Process Section 3. Output Section Zero speed switch Proximity logics N/O, N/C from contactors

How does it work ?:

How does it work ? The PLC regularly polls the devices in order to retrieve device readings and statuses. PLC Operations consist of three steps: 1. Input Scan: Scans the state of the inputs 2. Program Scan: Executes the program logic 3. Output Scan: Energize/de-energize the outputs

Need for artificial auto-control:

Need for artificial auto-control Any system has to function under specific norms in accordance with directed action 1.Complexity of the power system 2.Size of the system

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Modern PLCs can be programmed in a variety of ways, from ladder logic to more traditional programming languages such as BASIC and C. Five programming languages for programmable control systems: Programming FBD ( Function block diagram ) · LD ( Ladder diagram ) · ST ( Structured text ) · IL ( Instruction list ) · SFC ( Sequential function chart ).

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By selecting ladder logic as the main programming method, the amount of retraining needed for engineers and tradespeople was greatly reduced. LADDER LOGIC

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If we were to press "Start" button. input X1 would energize. sending "power" to Y1 output. Applys power to the motor contactor coil. The parallel Y1 contact will also "close," thus latching the "circuit" in an energized state STEP: 1 START BOTTON CLOSED MOTOR START-STOP CONTROL example.

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STEP:2 Now, if we release the "Start" button. X1 "contact" will return to its "open" state. But the motor will continue to run because the Y1 seal-in "contact" continues to provide "continuity" to "power" coil Y1, Thus keeping the Y1 output energized AFTER RELEASE START BUTTON

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STEP:3 To stop the motor, momentarily press the "Stop" pushbutton, which will energize the X2 input, "open" the normally-closed "contact, " breaking continuity to the Y1 "coil:" STOP BUTTON CLOSED

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STEP:4 When the "Stop" button is released, input X2 will de-energize, returns "contact" X2 to its normal "closed" state. The motor, however, will not start again until the "Start" button is actuated, Because the "seal-in" of Y1 has been lost. BACK TO INITIAL STATE

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PLCS AS POWER SYSTEMS Protection Devices In every sub station certain supervision, control and protection functions are necessary. Protection devices can be highly specialized PLCs that measure the current & voltages in an electrical substation, along with other status to detect situations that could endanger the equipment and trips the CB. Human interface for status and settings measurement transformers I r I s I t U r U s U T Programming interface trip relay communication to operator substation In addition, it records disturbances and sends the reports to the substation’s SCADA .

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Potential benefits of PLC Simulator option Flexibilty User friendly Sustainable Security Data import/export function

User interface::

User interface: A Human-Machine Interface is employed for the purpose of configuration, alarm reporting or everyday control for this purpose. Most modern PLCs can communicate over a network to some other system, such as a computer running a SCADA system

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Data import/export

Job Management:

Job Management

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From the substation to the control room Visual Substation 's client/server architecture provides you with a completely flexible and scalable solution. Use it as a substation HMI A SCADA system using PLC

Application to local distribution system:

Application to local distribution system Virtual schematic

PLC compared with other control systems:

PLC compared with other control systems PLCs are well-adapted to a certain range of automation tasks where changes to the system would be expected during its operational life. PLC applications are typically highly customized systems so the cost of a packaged PLC is low compared to the cost of a specific custom-built controller design. A microcontroller-based design would be appropriate where hundreds or thousands of units will be produced where the end-user would not need to alter the control. Very complex process control, such as used in the chemical industry, PLC’s with virtual plant display should be employed


Conclusions Specific application domains allow for tailored solutions (smaller models) Overall framework makes it easier to place and evaluate a certain validation approach. After the efficient functioning of PLC’s ,the control engineers innovated the new control systems “DISTRIBUTED CONTROL SYSTEMS (DCS)” to integrate all the individual automation systems in most complex process plants.

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