PLC SCADA REPORT PARAS SINGHAL

54







Chapter- 1
INTRODUCTION
1.1 INDUSTRIAL AUTOMATION:
Automation or industrial automation is the use of control systems such as computers, controllers to control industrial machinery and processes, to optimize productivity in the production of goods and delivery of services. Automation is a step beyond mechanization. Mechanization provides human operators with machinery to assist them with the muscular requirements of work, while automation greatly decreases the need for human sensory and mental requirements while increasing load capacity, speed, and repeatability.
Automation is basically the delegation of human control Function to technical equipment for
Increasing Productivity
Increasing Quality
Reducing Cost
Increasing Safety in working conditions
1.2 AUTOMATION IMPACTS:
It increases productivity and reduce cost.
It gives emphasis on flexibility and convertibility of manufacturing process. Hence gives manufacturers the ability to easily switch from manufacturing Product A to manufacturing product B without completely rebuilt the existing system/product lines.
Automation is now often applied primarily to increase quality in the manufacturing process, where automation can increase quality substantially.
Replacing humans in task done in dangerous environment .
1.3 DEVELOPMENT STAGES OF AUTOMATION:
Manual Control
Pneumatic Control
Hard wired logic Control
Electronic Control using Logic Gates
Programmable Logic Controller



1.3.1 Manual Control:
All the actions related to process control are taken by the operators .
Drawbacks:
Likely human errors and consequently its effect on quality of final product
The production, safety, energy consumption and usage of raw material are all subject to the correctness and accuracy of human action.
1.3.2 Pneumatic Control:
Industrial automation, with its machine and process control, had its origin in the 1920s with the advent of "Pneumatic Controllers".
Actions were controlled by a simple manipulation of pneumatic valves, which in turn were controlled by relays and switches.
Drawbacks:
Bulky and Complex System
Involves lot of rework to implement control logic
Longer project time
1.3.3 Hard wired logic control:
The contactor and Relays together with hardware timers and counters were used in achieving the desired level of automation.
Drawbacks
Bulky panels
Complex wiring
Longer project time
Difficult maintenance and troubleshooting.
1.3.4 Electronic Control using Logic Gates:
In 1960s with the advent of electronics, the logic gates started replacing the relays and auxiliary contactors in the control circuits. The hardware timers & counters were replaced by electronic timers.
Advantages:
Reduced space requirements
Energy saving
Less maintenance & greater reliability
Drawbacks:
Changes in control logic not possible
More project time

1.3.5 Programmable Logic Controllers:
In 1970s with the coming of microprocessors and associated peripheral chips, the whole process of control and automation underwent a radical change.
Instead of achieving the desired control or automation through physical wiring of control devices, in PLC it is achieved through a program or say software.
It can be effectively used in applications ranging from simple control like replacing small number of relays to complex automation problems


















Chapter- 2
PROGRAMMABLE LOGIC CONTROLLER

2.1 HISTORY OF PLC'S:
In the 1960's Programmable Logic Controllers were first developed to replace relays and relay control systems. Relays, while very useful in some applications, also have some problems. The primary reason for designing such a device was eliminating the large cost involved in replacing the complicated relay based machine control systems for major U.S. car manufacturers. These controllers eliminated the need of rewiring and adding additional hardware for every new configuration of logic. These, along with other considerations, led to the development of PLCs. plc was more improved in 1970's. In 1973 the ability to communicate between PLCs was added. This also made it possible to have the controlling circuit quite a ways away from the machine it was controlling. However, at this time the lack of standardization in PLCs created other problems. This was improved in the 1980's.The size of PLCs was also reduced then, thus using space even more efficiently. The 90's increased the collection of ways in which a PLC could be programmed (block diagrams, instruction list, C, etc.).

2.2 INTRODUCTION OF PLC'S:
A programmable logic controller (PLC) is an industrial computer control system that continuously monitors the state of input devices and makes decisions based upon a custom program to control the state of output devices.
It is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact.
They are used in many industries such as oil refineries, manufacturing lines, conveyor systems and so on, wherever there is a need to control devices the PLC provides a flexible way to "soft wire" the components together.
The basic units have a CPU (a computer processor) that is dedicated to run one program that monitors a series of different inputs and logically manipulates the outputs for the desired control. They are meant to be very flexible in how they can be programmed while also providing the advantages of high reliability (no program crashes or mechanical failures), compact and economical over traditional control systems.
In simple words, Programmable Logic Controllers are relay control systems put in a very small package. This means that one PLC acts basically like a bunch of relays, counters, timers, places for data storage, and a few various other things, all in one small package.

2.3 ARCITECTURE AND TERMINOLOGY OF PLC'S:
The PLC give output in order to switch things on or off. The PLC's output is proportionally activated according on the status of the system's feedback sensors and input terminal which is connected to PLC's. The decision to activate output are based on logic programmes. The logic programme stored in RAM or ROM memory. The PLC's also have same as computer, a CPU, data bus and address bus.
INPUT TERMINAL OUTPUT TERMINAL RUNCOMMONRAM/ROMCPUSOCKETS


























INPUT TERMINAL
OUTPUT TERMINAL
RUN
COMMON


RAM/ROM
CPU
SOCKETS
Fig 2.1: PLC's internal architecture
The next diagram shows a simplified diagram of PLC's structure. The central processing unit control everything according to a programme stored in a memory (RAM/ROM ).Everything is interconnected by two buses ,the address bus and data bus . The system must be able to communicate with external devices such as programmers,display moniter and a/d converter.

Fig 2.2: Simplified PLC's structure

Fig 2.3: Basic plc sections




PLCs contain three basic sections:
Central processing unit (CPU)
Memory: RAM, and ROM
Input/output module
Power supply

2.3.1 Central processing unit (C.P.U):
Like other computerized devices, there is a Central Processing Unit (CPU) in a PLC. The CPU, which is the "brain" of a PLC, does the following operations:
Updating inputs and outputs. This function allows a PLC to read the status of its input
terminals and energize or de-energize its output terminals.
Performing logic and arithmetic operations. A CPU conducts all the mathematic and
logic operations involved in a PLC.
Communicating with memory. The PLC's programs and data are stored in memory.
When a PLC is operating, its CPU may read or change the contents of memory locations.
Scanning application programs. An application program, which is called a ladder logic program, is a set of instructions written by a PLC programmer. The scanning function allows the PLC to execute the application program as specified by the programmer.
Communicating with a programming terminal. The CPU transfers program and data
between itself and the programming terminal.
A PLC's CPU is controlled by operating system software. The operating system software is a
group of supervisory programs that are loaded and stored permanently in the PLC's memory by the PLC manufacturer.

2.3.2 Input/ Output module:

2.3.2.1 Input module:
In smaller PLCs the inputs are normally built in and are specified when purchasing the PLC. For larger PLCs the inputs are purchased as modules, or cards, with 8 or 16 inputs of the same type on each card.The list below shows typical ranges for input voltages.
12-24 Vdc
100-120 Vac
10-60 Vdc
12-24 Vac/dc
5 Vdc (TTL)
200-240 Vac
48 Vdc
24 Vac
PLC input cards rarely supply power, this means that an external power supply is needed to supply power for the inputs and sensors. The example in See An AC Input Card shows how to connect an AC input card.

Fig 2.4: Input card connect with external power supply
In the example there are two inputs, one is a normally open push button, and the second is a temperature switch, or thermal relay. Both of the switches are powered by the hot output of the 24Vac power supply - this is like the positive terminal on a DC supply. Power is supplied to the left side of both of the switches. When the switches are open there is no voltage passed to the input card. If either of the switches are closed power will be supplied to the input.


Fig 2.5: Input side internal circuit
Plc input must convert a variety of logic level to the 5Vdc logic levels used on the data bus.This can be done with the circuit which is shiwn in fig (2.5).This circuit is ouptocoupler circuit.This circuit ellectrically isolate the external electrical circuitry from internal circuitry.Other circuit componant guard to reverse voltage polarity.

2.3.2.2 Output module:
As with input modules, output modules rarely supply any power, but instead act as switches. External power supplies are connected to the output card and the card will switch the power on or off for each output. Typical output voltages are listed below
120 Vac
24 Vdc
12-48 Vac
12-48 Vdc
5Vdc (TTL)
230 Vac
These cards typically have 8 to 16 outputs of the same type and can be purchased with different current ratings. A common choice when purchasing output cards is relays, transistors or triacs. Relays are the most flexible output devices. They are capable of switching both AC and DC outputs. But, they are slower (about 10ms switching is typical), they are bulkier and costly.

Fig 2.6: output card connected with verious load
In this example the outputs are connected to a low current light bulb (lamp) and a relay coil. Consider the circuit through the lamp, starting at the 24Vdc supply. When the output 07 is on, current can flow in 07 to the COM, thus completing the circuit, and allowing the light to turn on. If the output is off the current cannot flow, and the light will not turn on. The output 03 for the relay is connected in a similar way. When the output 03 is on, current will flow through the relay coil to close the contacts and supply 120Vac to the motor.


Fig 2.7: Ouput side internal circuit
Plc output must convert the 5Vdc logic levels on the plc data bus to external voltage levels. This can be done with the circuit which is shown in fig( 2.7).In this circuit the relay coil is enerzied by 5Vdc and close the relay contect and the output circuit is complete.


2.3.3 Memory:
The memory unit of a PLC is the registry where the programs are stored. The fundamental unit of memory is the word. Words are made up of bits. A bit is a single piece of data. It contains information on only two states (ON/OFF or YES/NO). Longer words contain more information within. Programs are combination of words that produce control logic.
To operate the PLC system there is a need for it to access the data to be processed and instructions, that is, the program, which informs it how the data is to be processed. Both are stored in the PLC memory for access during processing.
Plc memory has following types:
2.3.3.1 ROM(read only memory ):
ROMstores programs and data and cannot be changed after the memory chip has been manufactured. ROM memory is non-volatile, meaning that its contents will not be lost if power is lost. ROM is used by the PLC for the operating system.
2.3.3.2 RAM(random access memory):
RAM is designed so that information can be written into or read from the memory. RAM is used as a temporary storage area of data that may need to be quickly changed. RAM is volatile, meaning that the data stored in RAM will be lost if power is lost. A battery backup is required to avoid losing data in the event of a power loss.
2.3.3.3 EPROM (Erasable Programmable Read Only Memory):
This is memory that can be programmed to behave like ROM, but it can be erased with ultraviolet light and reprogrammed.
2.3.3.4 EEPROM (Electronically Erasable Programmable Read Only Memory):
This memory can store programs like ROM. It can be programmed and erased using a voltage, so it is becoming more popular than EPROMs.

2.3.4 Power supply:
PLCs and their constituting modules are equipped with power generated from a power supply. The power supply converts power line voltages into those required by the solid-state components. It may be integral or separately mounted . It drives the Central Processor Unit, I/O logic signals, memory unit and some peripheral devices. The expansion of I/O has led to increased power requirement of some PLCs.

2.4 Scan cycle and scan time:
2.4.1 Scan cycle :
PLC operates by continually scanning the program and acting upon the instructions , one at a time, to switch on or off the various outputs. In order to do this PLC first scans all the inputs and stores their states in memory. Then it carries out program scan and decides which outputs should be high according to the program logic. Then finally it updates these values to the output table, making the required outputs go high. At this point PLC checks its own operating system and if everything is ok, it goes back to scanning inputs all over again.

Fig 2.8: PLC scan cycle
Whenever a programe is executed in a plc,before changing any output state,the processor scan the input table and the entire programe,which gives rise to state of the output device according to the program logic.These value are then updated to the output table making the devices connected to the output module on or off. Hence PLC scan cycle consist of three step shown in a block diagram.

2.4.2 Scan time:
Time taken by PLC to execute these three step (checking input status,executing program,updating output status)is denoted by scan time.




2.5 PROGRAMMING LANGAUGE USED TO PROGRAM PLC:
While Ladder Logic is the most commonly used PLC programming language, but it is not the only one. Following table lists some of the Languages that are used to program a PLC.
Instruction List (IL)/Statement List(SL)
Structured Text(ST)
Sequential Functional Chart (SFC)
Ladder Diagram(LD).
Functional block Diagram (FBD)

2.5.1 Instruction List (IL)/Statement List(SL):
An instruction list (IL) consists of a series of instructions. Each instruction begins in a new line and contains an operator and, depending on the type of operation, one or more operands separated by commas.
In front of an instruction there can be an identification mark (label) followed by a colon (:).
A comment must be the last element in a line. Empty lines can be inserted between instructions.
Example:
LD 17
ST lint (* Kommentar *)
GE 5
JMPC next
LD idword
EQ istruct.sdword
STN test
next:

2.5.2 Structured Text (ST):
The Structured Text consists of a series of instructions which, as determined in high level languages, ("IF..THEN..ELSE") or in loops (WHILE..DO) can be executed.
Example:
IF value < 7 THEN
WHILE value < 8 DO
value:=value+1;
END_WHILE;
END_IF;

2.5.3 Sequential Function Chart (SFC):
The Sequential Function Chart (SFC) is a graphically oriented language which makes it possible to describe the chronological order of different actions within a program. For this the actions are assigned to step elements and the sequence of processing is controlled by transition elements.

Fig 2.9: Sequential Function Chart
2.5.4 Function Block Diagram (FBD):
The Function Block Diagram is a graphically oriented programming language. It works with a list of networks whereby each network contains a structure which represents either a logical or arithmetic expression, the call of a function block, a jump, or a return instruction.

Fig 2.9: Function Block Diagram



2.5.5 Ladder Diagram (LD):
The Ladder Diagram is also a graphics oriented programming language which approaches the
structure of an electric circuit. Ladder Diagram consists of a series of networks. Each network consists on the left side of a series of contacts which pass on from left to right the condition "ON" or "OFF" which correspond to the Boolean values TRUE and FALSE. To each contact belongs a Boolean variable. If this variable is TRUE, then condition pass from left to right.

Fig 2.10: ladder diagram
























Chapter- 3
COMMUNICATION/PROGRAMMING WITH SOFTWARE RSLINX

This chapter explains how to program the PLC. It describes how to write a program, how the program is structured and representation of the programming language.
3.1 PROGRAMING BY LADDER DIAGRAM:
Ladder logic is a method of drawing electrical logic schematics. It is now a graphical language very popular for programming Programmable Logic Controllers (PLCs). It was originally invented to describe logic made from relays. The name is based on the observation that programs in this language resemble ladders, with two vertical "rails "and a series of horizontal "rungs" between them. A program in the ladder logic, also called ladder diagram is similar to a schematic for a set of relay circuits.
The Ladder Diagram is also a graphics oriented programming language which approaches the
structure of an electric circuit. The Ladder Diagram consists of a series of networks. A network is limited on the left and right sides by a left and right vertical current line. In the middle is a circuit diagram made up of contacts, coils, and connecting lines.
Each network consists on the left side of a series of contacts which pass on from left to right the condition "ON" or "OFF" which correspond to the Boolean values TRUE and FALSE. To each contact belongs a Boolean variable. If this variable is TRUE, then the condition is passed from left to right along the connecting line. Otherwise the right connection receives the value OFF.

INPUT represented by I

OUTPUT represented by O.




3.2 Addressing method:
1 slot=32 bit=2 word (1 char./word=2 byte=16 bit)

3.2.1 Input addressing:
File letter:Slot number.Word number/Bit number
For example I:2.1/1

3.2.2 Output addressing:
File letter:Slot number.Word number/Bit number
For example O:2.1/1

3.3 GENERALLY USED INSTRUCTIONS & SYMBOL FOR PLC PROGRAMMING:

3.3.1 Input Instruction:
--[ ]-- This Instruction is Called XIC or Examine If Closed.
ie; If a NO switch is actuated then only this instruction will be true. If a NC switch is actuated then this instruction will not be true and hence output will not be generated.
--[\]-- This Instruction is Called XIO or Examine If Open
ie; If a NC switch is actuated then only this instruction will be true. If a NC switch is actuated then this instruction will not be true and hence output will not be generated.

3.3.2 Output Instruction:
--( )-- This Instruction Shows the States of Output(called OTE).
ie; If any instruction either XIO or XIC is true then output will be high. Due to high output a 24 volt signal is generated from PLC processor.
--(L)-- Output Latch (OTL)
OTL turns a bit on when the rung is executed, and this bit retains its state when the rung is not executed or a power cycle occurs.
--(U)-- Output Unlatch(OTU)
OTU turns a bit off when the rung is executed, and this bit retains its state when the rung is not executed or when power cycle occurs.

3.3.3 Rung:
Rung is a simple line on which instruction are placed and logics are created
E.g.; ---------------------------------------------

3.3.4 Timer:
Timer has three bit:
EN:Enable bit :
The Timer Enable (EN) bit is set immediately when the rung goes true. It stays set until the rung goes false.
TT:Timer timing bit :
The Timer Timing (TT) bit is set when the rung goes true. It stays set until the rung goes false or the Timer Done (DN) bit is set (i.e. when accumulated value equals preset value).
DN:Done bit:
The Timer Done (DN) bit is not set until the accumulated value is equal to the preset value. It stays set until the rung goes false.
Timer is three type:
TON 2. TOF 3. RTO
TON: Timer On
Counts time base intervals when the instruction is true.

Fig 3.1: Timer on

TOF: Timer off
Delay Counts time base intervals when the instruction is false.

Fig 3.2: Timer off
RTO: Retentive Timer
This type of timer does NOT reset the accumulated time when the input condition goes false. Rather, it keeps the last accumulated time in memory, and (if/when the input goes true again) continues timing from that point.

Fig 3.3: Retentive Timer

Addressing of timer:

Fig 3.4: Addressing of timer





Table 3.1: Status of bits in timer


3.3.5 Counter:
Counter has three bit:
Count Up bit (CU):
Set When Rung conditions are true and remains set till rung conditions go false or a RES instruction that has the same address as the CTD instruction is enabled.
Done bit ( DN):
Set When The accumulated value is => the preset value and remains set till The accumulated value becomes less than the preset value.
Overflow ( OV):
Set When Accumulated value wraps around to +32,768 (from: 32 767) and continues counting from there and remains set till a RES instruction that has same address as the CTD instruction is executed or the count is incremented greater than or equal to +32,767 with a CTU instruction.


Counter is two type :
CTU
CTD
3.3.5.1 CTU: Count Up
Increments the accumulated value at each false-to true transition and retains the accumulated value when the instruction goes false or when power cycle occurs.

Fig 3.4: Count Up
CTD: Count Down
Decrements the accumulate value at each false-to true transition and retains the accumulated value when the instruction goes false or when power cycle occurs.

Fig 3.5: Count Down

Addresing of counter:

Fig 3.4: Addressing of timer




3.3.7 RESET: --(RES)--
Resets the accumulated value and status bits of a timer or counter.
A C5:0
-------[ ]---------------------(RES)--------------------------
When A is true than counter C5:0 is reset.

3.4 BOOLEAN LOGIC DESIGN BY LADDER DIAGRAM:
3.4.1 AND logic:
Y0=X0.X1

Fig 3.5: AND logic ladder diagram

3.4.2 OR logic:
Y1=X0+X1

Fig 3.6: OR logic ladder diagram
3.4.3 NOT logic:
Y3=X0

Fig 3.7: NOT logic ladder diagram

3.4.4 NAND logic:
Y0=X0.X1

Fig 3.8: NAND logic ladder diagram
3.4.5 NOR logic:
Y1=X0+X1

Fig 3.9: NOR logic ladder diagram
3.4.6 X-OR logic:
Y2=X0 X1


Fig 3.10: XOR logic ladder diagram
3.4.7 X-NOR logic:
Y2=X0 X1




Fig 3.11: X-NOR logic ladder diagram

3.5 PROGRAMING AND OPERATIONS IN PLC:
To understannding the programing and operation we consider a example .
We have a car parking place which has five car parking capacity and we want to control the parking gate/light. We have one input sensor, one exit sensor,for power supply start stop push button,and for indication LED light
3.5.1 Making programme:
STEP: 1
Making start stop push button logic:
I:1.0/0B:1.0/0I:1.0/1B:1.0/0ABXXSTART BUTTONSTOP BUTTON







I:1.0/0
B:1.0/0
I:1.0/1
B:1.0/0
A
B
X
X
START BUTTON
STOP BUTTON
Fig 3.12: Push button logic ladder diagram
Here button a is start push button and b is stop push button and x is binary type output.
STEP: 2
Making input side sensor logic:

B:1.0/0XInput sensorI:1.0/2
Fig 3.13: Input sensor logic ladder diagram


B:1.0/0
X
Input sensor
I:1.0/2
Here we use one input sensor and one counter which is CTU (counter up) and take CTU preset value 5.
STEP: 3
Making exit side sensor logic:
I:1.0/3Exit sensor

I:1.0/3
Exit sensor
Fig 3.14: Output sensor logic ladder diagram
Here we use one Exit sensor and one counter which is CTD (counter down) and take CTD preset value 5.
STEP: 4
Making parking light (LED) control logic:
C5:0/DNO:1.0/0LED LIGHT



C5:0/DN
O:1.0/0
LED LIGHT
Fig 3.15: led light logic ladder diagram
Here we take done bit (DN) of counter for controlling the led light .

Operation:
After program making ,it is download in plc.This program store in plc memory.
When we push the start button than plc scan the input means input condition of button A is true(1).so the binary output is also true(1).
I:1.0/0B:1.0/0I:1.0/1B:1.0/0ABXXSTART BUTTONSTOP BUTTON











I:1.0/0
B:1.0/0
I:1.0/1
B:1.0/0
A
B
X
X
START BUTTON
STOP BUTTON
Fig 3.16: operation of Push button logic(on pressing NO switch)
When start button release than input condition of button A is false.
But the start button and binary input both are in parellel .The address of binary output and binary input are same so we get continuous supply.
I:1.0/0B:1.0/0I:1.0/1B:1.0/0ABXXSTART BUTTONSTOP BUTTON










I:1.0/0
B:1.0/0
I:1.0/1
B:1.0/0
A
B
X
X
START BUTTON
STOP BUTTON
Fig 3.17: operation of Push button logic (on releasing NO switch)

Binary output we can use as a input in next step ,its status is true.for sense the entering car we use a input sensor and for counting the car we use a CTU .
CTU address is C5:0 and take its preset value 5 because parking place capacity is 5. When first car enter then input sensor status goes true . Due to this CTU count one in it's accumulator value .but counter done bit does not true because accumulator value less than preset value.
Similarly when fifth car enter than CTU count it's accumulator value .Now counter done bit is true because accumlator value equal to preset value.
B:1.0/0XInput sensorI:1.0/2




B:1.0/0
X
Input sensor
I:1.0/2
Fig 3.18: operation of input sensor logic
When done bit goes true than LED output is true so parking light is on.
C5:0/DNO:1.0/0LED LIGHT





C5:0/DN
O:1.0/0
LED LIGHT
Fig 3.19: operation of led with input sensor logic
At exit side, one car is goes outside form parking place.Now four car is present in the parking place but CTU done bit is on so LED light is on.To remove this interlocking problem we use same address for both counter (CTU and CTD).
Both counter have same address so CTU accumulator value and CTD accumulator value both are same.
I:1.0/3Exit sensor5

I:1.0/3
Exit sensor

5
Fig 3.20: operation of exit sensor logic
At exit side for sense the car we use a exit sensor .when one car is exit. Than exit sensor status is true and CTD count and update the accumulator value .
Now both counter's accumulator value less than preset value so done bit goes false and parking light off .
B:1.0/0XInput sensorI:1.0/24I:1.0/3Exit sensor4C5:0/DNO:1.0/0LED LIGHT


B:1.0/0
X
Input sensor
I:1.0/2

4

I:1.0/3
Exit sensor

4



C5:0/DN
O:1.0/0
LED LIGHT
Fig 3.21: programme on window






Chapter -4
COMMUNICATION NETWORK ND APPLICATION
4.1 COMMUNICATION NETWORK OF PLC:
A proper interaction between devices, communication interfaces physical media and connecting products is possible only if correct network is chosen for communication.
The most commonly used network solutions are:
1. EtherNet/IP
ControlNet
DeviceNet
DH-485
DH+
Table 4.1: Communication network of plc
Use this network
If your application requires
EtherNet/IP network
Plant management (material handling)
Configuration, data collection, and control on a single, high-speed network
Time-critical applications with no established schedule
Internet connection
ControlNet network
High-speed transfer of time-critical data between controllers and I/O devices
Deterministic and repeatable data delivery
Media redundancy
Intrinsic safety
DeviceNet network
Connections of low-level devices directly to plant floor controllers, without interfacing them through I/O modules
Data sent as needed
More diagnostics for improved data collection and fault detection
Less wiring and reduced start-up time than a traditional, hard-wired system
DH-485 network
Connections to existing DH-485 networks
The DH-485 connection does support remote programming and monitoring via RSLogix 5000 software

Data Highway Plus
network
Plant-wide and cell-level data sharing with program maintenance
Data sent regularly
Transfer of information(messaging) between controllers

4.2 TOPOLOGY:
The structure of a network is called the topology. The basic network topologies shown in fig(4.1). The Bus and Ring topologies both share the same network wire. In the Star configuration each computer has a single wire for connection.

Fig 4.1: Network Topologies
In the Ring and Bus topologies the network control is distributed between all of the computers on the network. The wiring only uses a single loop or run of wire. But, because there is only one wire, the network will slow down significantly as traffic increases.
The Star topology requires more wire overall to connect each computer to an intelligent hub. But, the network interfaces in the computer become simpler, and the network becomes more reliable.
For a factory environment the bus topology is popular. The large number of wires required for a star configuration can be expensive and confusing. The loop of wire required for a ring topology is also difficult to connect.


Fig 4.2: Topology with repeater
Repeaters are used to boost the signal strength and allow the network to be larger.

Table 4.2: Comparision between communication protocols:
S.N.
Network
Max. No. node
Speed
Network length

Ethernet
1024
10-
1000Gbps
85m coax, 100m twisted pair, 400m-50km fiber

Controlnet
99
5Mbps
250m-1000m wire,3-30km fiber

Devicenet
64
125-
500Kbps
500m

DH485
32
19.2kbps
1.2 km

DH+
64
230kbps
3.048km

4.3 APPLICATIONS OF PLC:
In the present industrial world, a flexible system that can be controlled by user at site is preferred. Systems, whose logic can be modified but still, used without disturbing its connection to external world, is achieved by PLC. Utilizing the industrial sensors such as limit switches, ON-OFF switches, timer contact, counter contact etc., PLC controls the total system. The drive to the solenoid valves, motors, indicators, enunciators, etc are controlled by the PLCs.
The above said controlling elements (normally called as inputs of PLCs) and controlled elements (called as outputs of PLCs) exist abundantly in any industry. These inputs, outputs, timers, counters, auxiliary contacts are integral parts of all industries. As such, it is difficult to define where a PLC cannot be used.
Proper application of a PLC begins with conversion of information into convenient parameters to save money, time and effort and hence easy operation in plants and laboratories.
The areas where PLC is used maximum are as follows:
The batch processes in chemical, cement, food and paper industries which are sequential in nature, requiring time of event based decisions is controlled by PLCs.
In large process plants PLCs are being increasingly used for automatic start up and shut down of critical equipment. A PLC ensures that equipment cannot be started unless all the permissive conditions for safe start have seen established. It also monitors the conditions necessary for safe running of the equipment and trips the equipment whenever any abnormality in the system is detected.
The PLC can be programmed to function as an energy management system for boiler control for maximum efficiency and safety.
In automation of blender recliners
In automation of bulk material handling system at ports.
In automation for a ship unloaded.
Automation for wagon loaders.
For blast furnace charging controls in steel plants.
In automation of brick molding press in refractory.
In automation for galvanizing unit.
For chemical plants process control automation.
In automation of a rock phosphate drying and grinding system.
Modernization of boiler and turbo generator set.
Process visualization for mining application.
Criteria display system for power station.
As stored programmed automation unit for the operation of diesel generator sets.
In Dairy automation and food processing.
For a highly modernized pulp paper factory.
In automation system for the printing industry.
In automation of container transfer crane.
In automation of High-speed elevators.
In plastic molding process.
In automation of machine tools and transfer lines.
In Mixing operations and automation of packaging plants.
In compressed air plants and gas handling plants.
In fuel oil processing plants and water classification plants.
To control the conveyor/classifying system.
Thus PLC is ideal for application where plant machine interlock requirements are finalized at a later stage and need changes during engineering trial runs, commissioning or normal use.





Chapter- 5
SCADA
(SUPERVISORY CONTROL AND DATA ACQUISITION)
5.1 INTRODUCTION
SCADA stands for Supervisory Control And Data Acquisition. As the name indicates, it is not a full control system, but rather focuses on the supervisory level. As such, it is a purely software package that is positioned on top of hardware to which it is interfaced, in general via Programmable Logic Controllers (PLCs), or other commercial hardware modules.
SCADA systems are used to monitor and control a plant or equipment in industries such as telecommunications, water and waste control, energy, oil and gas refining and transportation. These systems encompass the transfer of data between a SCADA central host computer and a number of Remote Terminal Units (RTUs) and/or Programmable Logic Controllers (PLCs), and the central host and the operator terminals. A SCADA system gathers information (such as where a leak on a pipeline has occurred), transfers the information back to a central site, then alerts the home station that a leak has occurred, carrying out necessary analysis and control, such as determining if the leak is critical, and displaying the information in a logical and organized fashion.
SCADA systems consist of:
One or more field data interface devices, usually RTUs, or PLCs, which interface to field sensing devices and local control switchboxes and valve actuators
A communications system used to transfer data between field data interface devices and control units and the computers in the SCADA central host. The system can be radio, telephone, cable, satellite, etc., or any combination of these.
A central host computer server or servers (sometimes called a SCADA Center, master station, or Master Terminal Unit (MTU)
A collection of standard and/or custom software [sometimes called Human Machine Interface (HMI) software or Man Machine Interface (MMI) software] systems used to provide the SCADA central host and operator terminal application, support the communications system, and monitor and control remotely located field data interface devices.

Fig 5.1: Typical SCADA System

5.2 Types of SCADA:
1. D+R+N (Development +Run + Networking)
2. R+N (Run +Networking)
3. Factory focus (Networking)
5.3 Basic Features of SCADA:
Dynamic process Graphic
Alarm summery
Alarm history
Real time trend
Historical time trend
Security (Application Security)
Data base connectivity
Device connectivity
Scripts
Recipe management
Web Browser Client to View and Control
Web Browser based engineering
Dynamic process Graphic:
These graphics are commonly called as "SCREENS" and represent pictorial real time data of the process/plant/machine. Having no limitation on the number of screens for application is big advantage of SCADA.
Alarms Summery:
This is inbuilt graphic screen of SCADA which gives you consolidated alarm list with details like time, area, description, level and status.
Alarm history:
SCADA alarm history can be used for detail analysis. Alarms can be stored for data validity upto years together.
Real time trend:
These are graphical forms for analog or digital values with respect to time. Time can vary between few second to years.
Historical time trend:
Historical time trends are trends use history data for graphics. SCADA can help you get data in graphical format saved for many years.
Security:
This feature is nothing but access control of SCADA. SCADA can be used by many persons from many organization. So to control & limit access of everyone to every data of the process, we can have security levels designed.
Database connectivity:
SCADA stores the data in its own format depending of manufacturer. But user may require using this data in various formats like Microsoft Access, Excel Etc. This definitely calls for database connectivity between two different databases.
Device connectivity:
This can be used through communication protocols.
Scripts:
Backend of SCADA can be VB or C for which new block can be designed and complex calculations can be done using Scripting.

Recipe management:
For Batch process, you can have multiple recipes predefined in SCADA. For complex or more no of recipes you can use special batch software's available.
Web browser client for monitor and control:
Today in this internet based generation we always need access of our data at any point and any location. Web browser makes your SCADA available on internet where as per access granted and license purchased either you can monitor or control the SCADA

5.4 GENERATIONS OF SCADA SYSTEMS:
SCADA systems have evolved in parallel with the growth and sophistication of modern Computing technology. The following sections will provide a description of the following three generations of SCADA systems:
First Generation – Monolithic
Second Generation – Distributed
Third Generation – Networked
5.4.1 Monolithic SCADA Systems:
When SCADA systems were first developed, the concept of computing in general centered on "mainframe" systems. Networks were generally non-existent, and each centralized system stood alone. As a result, SCADA systems were standalone systems with virtually no connectivity to other systems. The Wide Area Networks (WANs) that were implemented to communicate with remote terminal units (RTUs) were designed with a single purpose in mind–that of communicating with RTUs in the field and nothing else. In addition, WAN protocols in use today were largely unknown at the time. The communication protocols in use on SCADA networks were developed by vendors of RTU equipment and were often proprietary. In addition, these protocols were generally very "lean", supporting virtually no functionality beyond that required scanning and controlling points within the remote device. Also, it was generally not feasible to intermingle other types of data traffic with RTU communications on the network.
Connectivity to the SCADA master station itself was very limited by the system vendor. Connections to the master typically were done at the bus level via a proprietary adapter or controller plugged into the Central Processing Unit (CPU) backplane. Redundancy in these first generation systems was accomplished by the use of two identically equipped mainframe systems, a primary and a backup, connected at the bus level.














Fig 5.2: First Generation SCADA Architecture

The stand by system's primary function was to monitor the primary and take over in the event of a detected failure. This type of standby operation meant that little or no processing was done on the standby system. Figure 3.1 shows a typical first generation SCADA architecture.

5.4.2 Distributed SCADA Systems:
The next generation of SCADA systems took advantage of developments and improvement in system miniaturization and Local Area Networking (LAN) technology to distribute the processing across multiple systems. Multiple stations, each with a specific function, were connected to a LAN and shared information with each other in real-time. These stations were typically of the mini-computer class, smaller and less expensive than their first generation processors. Some of these distributed stations served as communications processors, primarily communicating with field devices such as RTUs. Some served as operator interfaces, providing the human-machine interface (HMI) for system operators. Still others served as calculation processors or database servers. The distribution of individual SCADA system functions across multiple systems provided more processing power for the system as a whole than would have been available in a single processor.
The networks that connected these individual systems were generally based on LAN protocols and were not capable of reaching beyond the limits of the local environment. Some of the LAN protocols that were used were of a proprietary nature, where the vendor created its own network protocol or version thereof rather than pulling an existing one off the shelf. This allowed a vendor to optimize its LAN protocol for real-time traffic, but it limited (or effectively eliminated) the connection of network from other vendors to the SCADA LAN. Figure 11.2 depicts typical second generation SCADA architecture. Distribution of system functionality across network-connected systems served not only to increase processing power, but also to improve the redundancy and reliability of the system as a whole. Rather than the simple primary/standby failover scheme that was utilized in many first generation systems, the distributed architecture often kept all stations on the LAN in an online state all of the time.
For example, if an HMI station were to fail, another HMI station could be used to operate the system, without waiting for failover from the primary system to the secondary. The WAN used to communicate with devices in the field were largely unchanged by the development of LAN connectivity between local stations at the SCADA master. These external communications networks were still limited to RTU protocols and were not available for other types of network traffic. As was the case with the first generation of systems, the second generation of SCADA systems was also limited to hardware, software, and peripheral devices that were provided or at least selected by the vendor.



Fig 5.3: Second Generation SCADA Architecture

5.4.3 Networked SCADA Systems:
The current generation of SCADA master station architecture is closely related to that of the second generation, with the primary difference being that of open system architecture rather than a vendor controlled, proprietary environment. There are still multiple networked systems, sharing master station functions. There are still RTUs utilizing protocols that are vendor-proprietary. The major improvement in the third generation is that of opening the system architecture, utilizing open standards and protocols and making it possible to distribute SCADA functionality across a WAN and not just a LAN. Open standards eliminate a number of the limitations of previous generations of SCADA systems. The utilization of off-the-shelf systems makes it easier for the user to connect third party peripheral devices (such as monitors, printers, disk drives, tape drives, etc.) to the system and/or the network. As they have moved to "open" or "off-the-shelf" systems, SCADA vendors have gradually gotten out of the hardware development business. These vendors have looked to system vendors such as Compaq, Hewlett-Packard, and Sun Microsystems for their expertise in developing the basic computer platforms and operating system software. This allows SCADA vendors to concentrate their development in an area where they can add specific value to the system–that of SCADA master station software.
The major improvement in third generation SCADA systems comes from the use of WAN protocols such as the Internet Protocol (IP) for communication between the master station and communications equipment. This allows the portion of the master station that is responsible for communications with the field devices to be separated from the master station "proper" across a WAN. Vendors are now producing RTUs that can communicate with the master station using an Ethernet connection. Figure 5.4represents a networked SCADA system. Another advantage brought about by the distribution of SCADA functionality over a WAN is that of disaster survivability. The distribution of SCADA processing across a LAN in second-generation systems improves reliability, but in the event of a total loss of the facility housing the SCADA master, the entire system could be lost as well. By distributing the processing across physically separate locations, it becomes possible to build a SCADA system that can survive a total loss of any one location. For some organizations that see SCADA as a super-critical function, this is a real benefit.

Fig 5.4: Third Generation SCADA Architecture



5.5 ARCHITECTURE:
Generally SCADA system is a centralized system which monitors and controls entire area. It is purely software package that is positioned on top of hardware. A supervisory system gathers data on the process and sends the commands control to the process. For example, in the thermal power plant the water flow can be set to specific value or it can be changed according to the requirement. The SCADA system allows operators to change the set point for the flow, and enable alarm conditions incase of loss of flow and high temperature and the condition is displayed and recorded. The SCADA system monitors the overall performance of the loop. The SCADA system is a centralized system to communicate with both wire and wireless technology to Clint devices. The SCADA system controls can run completely all kinds of industrial process.
EX: If too much pressure in building up in a gas pipe line the SCADA system can automatically open a release valve.

5.5.1 Hardware Architecture:
The generally SCADA system can be classified into two parts:
Clint layer
Data server layer
The Clint layer which caters for the man machine interaction. The data server layer which handles most of the process data activities. The SCADA station refers to the servers and it is
composed of a single PC. The data servers communicate with devices in the field through process controllers like PLCs or RTUs. The PLCs are connected to the data servers either directly or via networks or buses. The SCADA system utilizes a WAN and LAN networks, the WAN and LAN consists of internet protocols used for communication between the master station and devices. The physical equipments like sensors connected to the PLCs or RTUs. The RTUs convert the sensor signals to digital data and sends digital data to master unit.

Fig 5.5: Hardware Architecture

5.5.2 Software Architecture:
Most of the servers are used for multitasking and real time database. The servers are responsible for data gathering and handling. The SCADA system consists of a software program to provide trending, diagnostic data, and manage information such as scheduled maintenance procedure, logistic information, detailed schematics for a particular sensor or machine and expert system troubleshooting guides. This means the operator can sea a schematic representation of the plant being controlled.
EX: alarm checking, calculations, logging and archiving; polling controllers on a set of parameter, those are typically connected to the server.

5.6 WORKING PROCEDURE OF SCADA SYSTEM:
The SCADA system performs the following functions:
Data Acquisitions
Data Communication
Information/Data presentation
Monitoring/Control
These functions are performed by sensors, RTUs, controller, communication network. The sensors are used to collect the important information and RTUs are used to send this information to controller and display the status of the system. According to the status of the system, the user can give command to other system components. This operation is done by the communication network.
5.6.1 Data Acquisitions:
Real time system consists of thousand of components and sensors. It is very important to know the status of particular components and sensors. For example, some sensors measure the water flow from the reservoir to water tank and some sensors measure the value pressure as the water is release from the reservoir.
5.6.2 Data Communication:
The SCADA system uses wired network to communicate between user and devices. The real
time applications use lot of sensors and components which should be control remotely. The SCADA system uses internet communications. All information is transmitted through internet using specific protocols. Sensor and relays are not able to communicate with the network protocols so RTUs used to communicate sensors and network interface.
5.6.3 Information/Data presentation:
The normal circuit networks have some indicators which can be visible to control but in the real time SCADA system, there are thousand of sensors and alarm which are impossible to be handled simultaneously. The SCADA system uses human machine interface (HMI) to provide all of the information gathered from the various sensors.
5.6.3.1 Human machine interface:
The SCADA system uses human machine interface. The information is displayed and monitored to be processed by the human. HMI provides the access of multiple control units which can be PLCs and RTUs. The HMI provides the graphical presentation of the system. For example, it provides the graphical picture of the pump connected to the tank. The user can see the flow of the water and pressure of the water. The important part of the HMI is an alarm system which is activated according to the predefined values.


Fig 5.5: Human machine interface
For example: The tank water level alarm is set 60% and 70% values. If the water level reaches above 60% the alarm gives normal warning and if the water level reach above 70% the alarm gives critical warning.
5.6.4 Monitoring/Control:
The SCADA system uses different switches to operate each device and displays the status at
the control area. Any part of the process can be turned ON/OFF from the control station using these switches. SCADA system is implemented to work automatically without human intervention but at critical situations it is handled by man power.

5.7 SCADA FOR REMOTE INDUSTRIAL PLANT:
In large industrial establishments many process occur simultaneously and each needs to be monitored, which is actually a complex task. The SCADA systems are used to monitor and control the equipments in the industrial processes which include water distribution, oil distribution and power distribution. The main aim of this project is to process the real time data and control the large scale remote industrial environment. For an example the temperature sensors are connected to the plc , which is connected to the PC at the front end and software is loaded on the computer. The data is collected from the temperature sensors. The temperature sensors continuously send the signal to the plc which accordingly displays these values on its front panel. One can set the parameters like low limit and high limit on the computer screen. When the temperature of a sensor goes above set point ,the plc send a command to the corresponding relay. The heaters connected through relay contacts are turned OFF and ON.
Chapter- 6
DESIGN SCADA WITH INTOUCH WONDERWARE SOFTWARE AND APPLICATION
SCADA is main interface between your control system and Operator. Maximum data and
features available on SCADA give you better control and clarity about the system. SCADA
needs to read data from various devices like:-
PLC/Controllers
RTU
Energy meters/Load managers/Data loggers
Field instruments like Flow meters and postioners
Each of above data communicates with SCADA on various protocols . SCADA reads or
writes the data in format of tags.

6.1 TAG:
Tag can be data representation of bit, byte, word or any array which is read from source
through communication protocol. Tag can be representation of digital or analog value
depending upon TAG configuration.

6.2 INTOUCH WONDERWARE SCADA SOFTWARE:
First we crate the animated object from "Wizard Selection" tool than specify tag name as require. We can create almost any screen animation effect imaginable. We can make objects
change color, size, location, visibility, fill level, and so on.
Animation link selection dialog box are shown in fig (6.1)


Fig 6.1: Animation Link Selection Dialog Box
6.2.1 TOUCH LINK
User Input touch links:
Discrete: Used to control the value of a discrete tagname.
Analog: Used to input the value of an analog (integer or real) tagname.
String: Used to create an object into which a string message may be input.
Sliders touch links:
Vertical& Horizontal:
we can move the slider position horizontally or vertically.
Touch Pushbutton links:
Discrete Value:
Used to make any object or symbol into a pushbutton that controls the state of a discrete tagname. Pushbutton actions can be set, reset, toggle, momentary on (direct) and momentary off (reverse) types.
Action:
Allows any object, symbol or button to have up to three different action scripts linked to it; On Down, While Down and On Up.
Show Window:
Used to make an object or symbol into a button that opens one or more windows when it is clicked or touched.
Hide Window:
Used to make an object or symbol into a button that closes one or more windows when it is clicked or touched.


Fig 6.2: push button dialog box
6.2.2 COLOR LINKS:
Discrete:
Used to control the fill, line and text colors attributes of an object or symbol that is linked to the value of a discrete expression.
Analog:
The line, fill, and text color of an object or symbol can be linked to the value of an analog tagname (integer or real) or an analog expression. Five value ranges are defined by specifying four breakpoints. Five different colors can be selected which will be displayed as the value range changes.
Discrete Alarm:
The text, line, and fill color of an object can all be linked to the alarm state of a tagname, Alarm Group, or Group Variable. This color link allows a choice of two colors; one for the normal state and one for the alarm state of the tagname. This link can be used for both analog and discrete tagnames. If it is used with an analog tagname, it responds to any alarm condition of the tagname
Analog Alarm:
The text, line, and fill color of an object can all be linked to the alarm state of an analog tagname, Alarm Group, or Group Variable. Allows a specific color to be set for the normal state as well as a separate color for each alarm condition defined for the tagname.

Fig 6.3: Fill color dialog box
6.2.3 OBJECT SIZE LINKS:
We use Object Size links to vary the height and/or width of an object according to the value of an analog (integer or real) tagname or analog expression. Size links provide the ability to control the direction in which the object enlarges in height and/or width by setting the "anchor" for the link. Both height and width links can be attached to the same object.

Fig 6.4: object height dialog box
6.2.4 PERCENT FILL LINKS:
We use Percent Fill Links to provide the ability to vary the fill level of a filled shape (or a symbol containing filled shapes) according to the value of an analog tagname or an expression that computes to an analog value. For example, this link may be used to show the level of liquids in a vessel. An object or symbol may have a horizontal fill link, a vertical fill link, or both.

Fig 6.5: vertical fill dialog box
6.2.5 LOCATION LINKS:
We use Location Links to make an object automatically move horizontally, vertically, or in both directions in response to changes in the value of an analog tagname or expression

Fig 6.6: horizontal location dialog box
6.2.6 MISCELLANEOUS LINKS:
There are four type of miscellaneous links.
Visibility:
Use to control the visibility of an object based on the value of a discrete tagname or expression.
Blink:
Used to make an object blink based on the value of a discrete tagname or expression.
Orientation:
Used to make an object rotate based on the value of a tagname or expression.
Disable:
Used to disable the touch functionality of objects based on the value of a tagname or expression.
6.2.7 VALUE DISPLAY LINKS:
Value Display Links provide the ability to use a text object to display the value of a discrete, analog, or string tagname. There are three types:
Discrete :
Uses the value of a discrete expression to display an On or Off user defined message in a text object.
Analog:
Displays the value of an analog expression in a text object.
String:
Displays the value of a string expression in a text object.

6.3 APPLICATIONS OF SCADA:
SCADA systems can be relatively simple, such as one that monitors environmental
conditions of a small office building, or incredibly complex, such as a system that monitors all the activity in a nuclear power plant or the activity of a municipal water system.
SCADA monitors and controls industrial, infrastructure, or facility-based processes, as described below:
Industrial processes include those of manufacturing, production, power generation,
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.
Industries that are catered to are:
Automotive
Building Automation
Cement & Glass
Chemical
Electronics
Food and Beverage
Machinery & Manufacturing
Aerospace & Defense
Metals & Mining
Oil & Gas
Pharmaceutical
Power, Utilities & Generation
Transportation
Water & Wastewater

6.4 ADVANTAGES:
The SCADA system provides onboard mechanical and graphical information
The SCADA system is easily expandable. We can add set of control units and sensors according to the requirement.
The SCADA system ability to operate critical situations















FUTURE SCOPE
The PLC offers a compromise between advance control techniques and present day technology. It is extremely difficult to forecast the rate and form of progress of PLCs, but there is strong evidence that development is both rapid and cumulative. Though a PLC is not designed to replace a computer, it is useful and cost effective for medium sized control systems. With the capability of functioning as local controllers in distributed control systems, PLCs will retain their application in large process plants.
A further development of PLCs leads to the development of programmable function controller (PFC) is compatible to PCs and directly controls the desired functions.
In India every process industry is replacing relay control systems by PLCs and will go for PFCs in near future. In the near future every flats and offices may possess PFCs to control room temperature, as elevator controller, maintain water tank levels, as small telephone exchange etc.


















CONCLUSION
Thus it can be concluded using cost benefit analysis and some technical aspects being included in the report that through total automation solution, synthetic chemical plant following gain points can be achieved:
Enhanced control over plant operation
Better usage of utilities like boiler etc.
Higher productivity
Improved skill of workmen
Better monitoring leading to reduced maintenance
Greater safety of plant and personal


















REFERENCES
International Conference paper on "WHAT IS SCADA?"A. Daneels,W.Salter.
Rockwell automation software manual.
Inouch wonderware software manual.
Wikipedia "PLC and SCADA".