ACKNOWLEDGEMENT

I would like to express my gratitude to all those who gave me the possibility to complete

this report. I like to thank my HOD giving me permission to commence this report in the first

instance, to do the necessary experimental work and to use departmental data. I am thanking to

all my teachers who gave me the required knowledge, skill and a mental approach within the

training schedule and encouraged the developing interest in this field. I am bound to my Head of

Department of Electrical & Electronics Engineering also my training incharge Er. R.K. Sharma

(HOD) for constant and stimulating support.

I am thankful to my training coordinator Er. Krishan Arora who supported me in my report work.

I want to thank them for all their help, support, interest and valuable hints as well as for the close

look at the final version of the report for English style and grammar, correcting both and offering

suggestions for improvement.

ABSTRACT

Automation has been of high priority for the manufacturing sector, from Ford's first set of

Model-T Assembly lines in the early 1920s to the modern factory floor. With appropriate

automation, the aim was to rationalize the production and keep the process under control.

Instrumentation for measuring process variables assumed a significant role in meeting such

goals. The development of new sensors and instruments took place in stages concurrent with

advancements in science and technology. This paper comprehensively reviews the evolution of

industrial automation. Essentially, it reviews the milestones in the industrial automation and

control systems, the emergence of Distributed Control Systems (DCSs), the advanced control

architecture, the non-conventional technologies for the future and finally the benefits from the

networked system.

An industrial SCADA system will be used for the development of the controls of LHC

experiments. Here we describe the SCADA systems in terms of their architecture, their interface

to the process hardware, the functionality and the application development facilities they

provide. Some attention is also aid to industrial standards to which they abide their planned

evolution as well as the benefits of their use.

AUTOMATION – HISTORY

Ideas for ways of automating tasks have been in existence since the time of the ancient Greeks.

The Greek inventor Hero (fl. about A.D. 50), for example, is credited with having developed an

automated system that would open a temple door when a priest lit a fire on the temple altar. The

real impetus for the development of automation came, however, during the Industrial Revolution

of the early eighteenth century. Many of the steam-powered devices built by James Watt,

Richard Trevithick, Richard Arkwright, Thomas Savory, Thomas Newcomen, and their

contemporaries were simple examples of machines capable of taking over the work of humans.

One of the most elaborate examples of automated machinery developed during this period was

the draw loom designed by the French inventor Basile Bouchon in 1725. The instructions for the

operation of the Bouchon loom were recorded on sheets of paper in the form of holes. The

needles that carried thread through the loom to make cloth were guided by the presence or

absence of those holes. The manual process of weaving a pattern into a piece of cloth through the

work of an individual was transformed by the Bouchon process into an operation that could be

performed mindlessly by merely stepping on a pedal.

CHAPTER – 1 AUTOMATION

INTRODUCTION

Automation is the use of control systems (such as numerical control, programmable logic

control, and other industrial control systems), in concert with other applications of information

technology (such as computer-aided technologies [CAD, CAM]), to control industrial machinery

and processes, reducing the need for human intervention. In the scope of industrialization,

automation is a step beyond mechanization. Whereas mechanization provided human operators

with machinery to assist them with the muscular requirements of work, automation greatly

reduces the need for human sensory and mental requirements as well. Processes and systems can

also be automated.

Types of Automation

Automated machines can be subdivided into two large categories—open-loop and closed-loop

machines, which can then be subdivided into even smaller categories. Open-loop machines are

devices that, once started, go through a cycle and then stop. A common example is the automatic

dishwashing machine. Once dishes are loaded into the machine and a button pushed, the machine

goes through a predetermined cycle of operations: pre-rinse, wash, rinse, and dry, for example. A

human operator may have choices as to which sequence the machine should follow—heavy

wash, light wash, warm and cold, and so on—but each of these operations is alike in that the

machine simply does the task and then stops. Many of the most familiar appliances in homes

today operate on this basis. A microwave oven, a coffee maker, and a CD player are examples.

Larger, more complex industrial operations also use open-cycle operations. For example, in the

production of a car, a single machine may be programmed to place a side panel in place on the

car and then weld it in a dozen or more locations. Each of the steps involved in this process—

from placing the door properly to each of the different welds—takes place according to

instructions programmed into the machine.

Other category in which automation is divided is:

Scientific Automation ( used by scientists)

Industrial Automation ( building management system)

Office Automation ( used by non technical staff)

Role of Computers in Automation

Since the 1960s, the nature of automation has undergone dramatic changes as a result of the

availability of computers. For many years, automated machines were limited by the amount of

feedback data they could collect and interpret. Thus, their operation was limited to a relatively

small number of alternatives. When an automated machine is placed under the control of a

computer, however, that disadvantage disappears. The computer can analyze a vast number of

sensory inputs from a system and decide which of many responses it should make.

Layout of Industrial Automation

AUTOMATION - APPLICATION

Manufacturing companies in virtually every industry are achieving rapid increases in

productivity by taking advantage of automation technologies. When one thinks of automation in

manufacturing, robots usually come to mind. The automotive industry was the early adopter of

robotics, using these automated machines for material handling, processing operations, and

assembly and inspection. Donald A. Vincent, executive vice president, Robotic Industries

Association, predicts a greater use of robots for assembly, paint systems, final trim, and parts

transfer will be seen in the near future.

One can break down automation in production into basically three categories: fixed automation,

programmable automation, and flexible automation. The automotive industry primarily uses

fixed automation, Also known as "hard automation," this refers to an automated production

facility in which the sequence of processing operations is fixed by the equipment layout. A good

example of this would be an automated production line where a series of workstations are

connected by a transfer system to move parts between the stations. What starts as a piece of sheet

metal in the beginning of the process, becomes a car at the end.

Programmable automation is a form of automation for producing products in batches. The

products are made in batch quantities ranging from several dozen to several thousand units at a

time. For each new batch, the production equipment must be reprogrammed and changed over to

accommodate the new product style.

Flexible automation is an extension of programmable automation. Here, the variety of products

is sufficiently limited so that the changeover of the equipment can be done very quickly and

automatically. The reprogramming of the equipment in flexible automation is done off-line; that

is, the programming is accomplished at a computer terminal without using the production

equipment itself.

AUTOMATION- ADVANTAGES

1. Replacing human operator in tedious task.

2. Replacing humans in tasks that should be done in dangerous environment.

3. Making tasks that are beyond human capabilities such as handle too heavy

loads, too large objects, too hot or cold substances or the requirement to make things too

fast or too slow.

4. Economy improvement- sometimes some kinds of automation imply improves in

economy of enterprises, society or most of the humankind.

DISADVANTAGES

1. Technology limits- nowadays technology is not able to automate all desired task.

2. Initial costs are relative high.

CHAPTER – 2 PROGRAMMABLE LOGIC CONTROLLER

INTRODUCTION

A programmable logic controller (PLC) or programmable controller is a digital computer

used for automation of electromechanical processes, such as control of machinery on factory

assembly lines, amusement rides, or lighting fixtures. PLCs are used in many industries and

machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output

arrangements, extended temperature ranges, immunity to electrical noise, and resistance to

vibration and impact. Programs to control machine operation are typically stored in battery-

backed or non-volatile memory. A PLC is an example of a real time system since output results

must be produced in response to input conditions within a bounded time, otherwise unintended

operation will result.

History

The PLC was invented in response to the needs of the American automotive manufacturing

industry. Programmable controllers were initially adopted by the automotive industry where

software revision replaced the re-wiring of hard-wired control panels when production models

changed.

Before the PLC, control, sequencing, and safety interlock logic for manufacturing automobiles

was accomplished using hundreds or thousands of relays, cam timers, and drum sequencers and

dedicated closed-loop controllers. The process for updating such facilities for the yearly model

change-over was very time consuming and expensive, as electricians needed to individually

rewire each and every relay.

In 1968 GM Hydramatic (the automatic transmission division of General Motors) issued a

request for proposal for an electronic replacement for hard-wired relay systems. The winning

proposal came from Bedford Associates of Bedford, Massachusetts. The first PLC, designated

the 084 because it was Bedford Associates' eighty-fourth project, was the result. Bedford

Associates started a new company dedicated to developing, manufacturing, selling, and servicing

this new product: Modicon, which stood for MOdular DIgital CONtroller. One of the people

who worked on that project was Dick Morley, who is considered to be the "father" of the PLC.

The Modicon brand was sold in 1977 to Gould Electronics, and later acquired by German

Company AEG and then by French Schneider Electric, the current owner.

Vendors of PLCs

Allenbradley( micrologix, SLC, Contrologix)

Schneider(modicon, zelio)

Siemens(s7-200, s7-300)

OMRON

GE-FANUC

Mitsubishi

Features of PLC

Control panel with PLC (grey elements in the center). The unit consists of separate elements,

from left to right; power supply, controller, relay units for in- and output

The main difference from other computers is that PLCs are armored for severe conditions (such

as dust, moisture, heat, cold) and have the facility for extensive input/output (I/O) arrangements.

These connect the PLC to sensors and actuators. PLCs read limit switches, analog process

variables (such as temperature and pressure), and the positions of complex positioning systems.

Some use machine vision. On the actuator side, PLCs operate electric motors, pneumatic or

hydraulic cylinders, magnetic relays, solenoids, or analog outputs. The input/output

arrangements may be built into a simple PLC, or the PLC may have external I/O modules

attached to a computer network that plugs into the PLC.

With each module having sixteen "points" of either input or output, this PLC has the ability to

monitor and control dozens of devices. Fit into a control cabinet, a PLC takes up little room,

especially considering the equivalent space that would be needed by electromechanical relays to

perform the same functions:

The main difference from other computers is that PLC are armored for severe condition (dust,

moisture, heat, cold, etc) and has the facility for extensive input/output (I/O) arrangements.

These connect the PLC to sensors and actuators. PLCs read limit switches, analog process

variables (such as temperature and pressure), and the positions of complex positioning systems.

Some even use machine vision. On the actuator side, PLCs operate electric motors, pneumatic or

hydraulic cylinders, magnetic relays or solenoids, or analog outputs. The input/output

arrangements may be built into a simple PLC, or the PLC may have external I/O modules

attached to a computer network that plugs into the PLC.

Many of the earliest PLCs expressed all decision making logic in simple ladder logic which

appeared similar to electrical schematic diagrams. The electricians were quite able to trace out

circuit problems with schematic diagrams using ladder logic. This program notation was chosen

to reduce training demands for the existing technicians. Other early PLCs used a form of

instruction list programming, based on a stack-based logic solver.

The functionality of the PLC has evolved over the years to include sequential relay control,

motion control, process control, distributed control systems and networking. The data handling,

storage, processing power and communication capabilities of some modern PLCs are

approximately equivalent to desktop computers

Development

Early PLCs were designed to replace relay logic systems. These PLCs were programmed in

"ladder logic", which strongly resembles a schematic diagram of relay logic. This program

notation was chosen to reduce training demands for the existing technicians. Other early PLCs

used a form of instruction list programming, based on a stack-based logic solver.

Modern PLCs can be programmed in a variety of ways, from ladder logic to more traditional

programming languages such as BASIC and C. Another method is State Logic, a very high-level

programming language designed to program PLCs based on state transition diagrams.

Functionality

The functionality of the PLC has evolved over the years to include sequential relay control,

motion control, process control, distributed control systems and networking. The data handling,

storage, processing power and communication capabilities of some modern PLCs are

approximately equivalent to desktop computers. PLC-like programming combined with remote

I/O hardware, allow a general-purpose desktop computer to overlap some PLCs in certain

applications.

Programming

PLC programs are typically written in a special application on a personal computer, then

downloaded by a direct-connection cable or over a network to the PLC. The program is stored in

the PLC either in battery-backed-up RAM or some other non-volatile flash memory. Often, a

single PLC can be programmed to replace thousands of relays.

IEC 61131-3 currently defines five programming languages for programmable control systems:

FBD (Function block diagram)

LD (Ladder diagram)

ST (Structured text, similar to the Pascal programming language)

IL (Instruction list, similar to assembly language)

SFC (Sequential function chart)

While the fundamental concepts of PLC programming are common to all manufacturers,

differences in I/O addressing, memory organization and instruction sets mean that PLC programs

are never perfectly interchangeable between different makers. Even within the same product line

of a single manufacturer, different models may not be directly compatible.

Wiring In a PLC

Block diagram of a PLC

Generation of Input Signal

Inside the PLC housing, connected between each input terminal and the Common terminal, is an

opto-isolator device (Light-Emitting Diode) that provides an electrically isolated "high" Logic

signal to the computer's circuitry (a photo-transistor interprets the LED's light) when there is 120

VAC power applied between the respective input terminal and the Common terminal. An

indicating LED on the front panel of the PLC gives visual indication of an "energized" input

:

Diagram Showing Energized input terminal X1

Generation of Output Signal

Output signals are generated by the PLC's computer circuitry activating a switching device

(transistor, TRIAC, or even an electromechanical relay), connecting the "Source" terminal to any

of the "Y-" labeled output terminals. The "Source" terminal, correspondingly, is usually

connected to the L1 side of the 120 VAC power source. As with each input, an indicating LED

on the front panel of the PLC gives visual indication of an "energized" output

In this way, the PLC is able to interface with real-world devices such as switches and solenoids.

The actual logic of the control system is established inside the PLC by means of a computer

program. This program dictates which output gets energized under which input conditions.

Although the program itself appears to be a ladder logic diagram, with switch and relay symbols,

there are no actual switch contacts or relay coils operating inside the PLC to create the logical

relationships between input and output. These are imaginary contacts and coils, if you will. The

program is entered and viewed via a personal computer connected to the PLC's programming

port.

Diagram Showing Energized Output Y1

PLC compared with other control systems

PLCs are well-adapted to a range of automation tasks. These are typically industrial processes in

manufacturing where the cost of developing and maintaining the automation system is high

relative to the total cost of the automation, and where changes to the system would be expected

during its operational life. PLCs contain input and output devices compatible with industrial pilot

devices and controls; little electrical design is required, and the design problem centers on

expressing the desired sequence of operations. 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. On the other hand, in the case of mass-produced goods, customized control

systems are economic due to the lower cost of the components, which can be optimally chosen

instead of a "generic" solution, and where the non-recurring engineering charges are spread over

thousands or millions of units.

Very complex process control, such as used in the chemical industry, may require algorithms and

performance beyond the capability of even high-performance PLCs. Very high-speed or

precision controls may also require customized solutions; for example, aircraft flight controls.

Programmable controllers are widely used in motion control, positioning control and torque

control. Some manufacturers produce motion control units to be integrated with PLC so that G-

code (involving a CNC machine) can be used to instruct machine movements.

Digital and analog signals

Digital or discrete signals behave as binary switches, yielding simply an On or Off signal (1 or 0,

True or False, respectively). Push buttons, limit switches, and photoelectric sensors are examples

of devices providing a discrete signal. Discrete signals are sent using either voltage or current,

where a specific range is designated as On and another as Off. For example, a PLC might use 24

V DC I/O, with values above 22 V DC representing On, values below 2VDC representing Off,

and intermediate values undefined. Initially, PLCs had only discrete I/O.

Analog signals are like volume controls, with a range of values between zero and full-scale.

These are typically interpreted as integer values (counts) by the PLC, with various ranges of

accuracy depending on the device and the number of bits available to store the data. As PLCs

typically use 16-bit signed binary processors, the integer values are limited between -32,768 and

+32,767. Pressure, temperature, flow, and weight are often represented by analog signals. Analog

signals can use voltage or current with a magnitude proportional to the value of the process

signal. For example, an analog 4-20 mA or 0 - 10 V input would be converted into an integer

value of 0 - 32767.

Current inputs are less sensitive to electrical noise (i.e. from welders or electric motor starts) than

voltage inputs.

Example

As an example, say a facility needs to store water in a tank. The water is drawn from the tank by

another system, as needed, and our example system must manage the water level in the tank.

Using only digital signals, the PLC has two digital inputs from float switches (Low Level and

High Level). When the water level is above the switch it closes a contact and passes a signal to

an input. The PLC uses a digital output to open and close the inlet valve into the tank.

When the water level drops enough so that the Low Level float switch is off (down), the PLC

will open the valve to let more water in. Once the water level rises enough so that the High Level

switch is on (up), the PLC will shut the inlet to stop the water from overflowing. This rung is an

example of seal in logic. The output is sealed in until some condition breaks the circuit.

|| Low Level High Level Fill Valve ||------[/]------|------[/]----------------------(OUT)---------|| | || | || | || Fill Valve | ||------[ ]------| || || |

An analog system might use a water pressure sensor or a load cell, and an adjustable (throttling)

dripping out of the tank, the valve adjusts to slowly drip water back into the tank.

In this system, to avoid 'flutter' adjustments that can wear out the valve, many PLCs incorporate

"hysteresis" which essentially creates a “dead band” of activity? A technician adjusts this dead

band so the valve moves only for a significant change in rate. This will in turn minimize the

motion of the valve, and reduce its wear.

A real system might combine approaches, using float switches and simple valves to prevent

spills, and a rate sensor and rate valve to optimize refill rates and prevent water hammer. Backup

and maintenance methods can make a real system very complicated.

CHAPTER – 3 PROGRAMMING WITH PLC

Early PLCs, up to the mid-1980s, were programmed using proprietary programming panels or

special-purpose programming terminals, which often had dedicated function keys representing

the various logical elements of PLC programs. Programs were stored on cassette tape cartridges.

Facilities for printing and documentation were very minimal due to lack of memory capacity.

More recently, PLC programs are typically written in a special application on a personal

computer, then downloaded by a direct-connection cable or over a network to the PLC. The very

oldest PLCs used non-volatile magnetic core memory but now the program is stored in the PLC

either in battery-backed-up RAM or some other non-volatile flash memory.

Early PLCs were designed to be used by electricians who would learn PLC programming on the

job. These PLCs were programmed in "ladder logic", which strongly resembles a schematic

diagram of relay logic. Modern PLCs can be programmed in a variety of ways, from ladder logic

to more traditional programming languages such as BASIC and C. Another method is State

Logic, a Very High Level Programming Language designed to program PLCs based on State

Transition Diagrams.

Ladder logic

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 ladder logic, also called a ladder diagram, is similar to a schematic for a set of

relay circuits. An argument that aided the initial adoption of ladder logic was that a wide variety

of engineers and technicians would be able to understand and use it without much additional

training, because of the resemblance to familiar hardware systems. (This argument has become

less relevant given that most ladder logic programmers have a software background in more

conventional programming languages, and in practice implementations of ladder logic have

characteristics — such as sequential execution and support for control flow features — that make

the analogy to hardware somewhat imprecise.)

Ladder logic is widely used to program PLCs, where sequential control of a process or

manufacturing operation is required. Ladder logic is useful for simple but critical control

systems, or for reworking old hardwired relay circuits. As programmable logic controllers

became more sophisticated it has also been used in very complex automation systems.

Ladder logic can be thought of as a rule-based language, rather than a procedural language. A

"rung" in the ladder represents a rule. When implemented with relays and other

electromechanical devices, the various rules "execute" simultaneously and immediately. When

implemented in a programmable logic controller, the rules are typically executed sequentially by

software, in a loop. By executing the loop fast enough, typically many times per second, the

effect of simultaneous and immediate execution is obtained. In this way it is similar to other rule-

based languages, like spreadsheets or SQL. However, proper use of programmable controllers

requires understanding the limitations of the execution order of rungs.

Example of a simple ladder logic program

The language itself can be seen as a set of connections between logical checkers (relay contacts)

and actuators (coils). If a path can be traced between the left side of the rung and the output,

through asserted (true or "closed") contacts, the rung is true and the output coil storage bit is

asserted (1) or true. If no path can be traced, then the output is false (0) and the "coil" by analogy

to electromechanical relays is considered "de-energized". The analogy between logical

propositions and relay contact status is due to Claude Shannon.

Ladder logic has "contacts" that "make" or "break" "circuits" to control "coils." Each coil or

contact corresponds to the status of a single bit in the programmable controller's memory. Unlike

electromechanical relays, a ladder program can refer any number of times to the status of a single

bit, equivalent to a relay with an indefinitely large number of contacts.

So-called "contacts" may refer to inputs to the programmable controller from physical devices

such as pushbuttons and limit switches, or may represent the status of internal storage bits which

may be generated elsewhere in the program.

Each rung of ladder language typically has one coil at the far right. Some manufacturers may

allow more than one output coil on a rung.

--( )-- a regular coil, true when its rung is true

--(\)-- a "not" coil, false when its rung is true

--[ ]-- A regular contact, true when its coil is true (normally false)

--[\]-- A "not" contact, false when its coil is true (normally true)

The "coil" (output of a rung) may represent a physical output which operates some device

connected to the programmable controller, or may represent an internal storage bit for use

elsewhere in the program.

Generally Used Instructions & symbol For PLC Programming

Input Instruction

--[ ]-- This Instruction is Called IXC 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 IXO 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.

Output Instruction

--( )-- This Instruction Shows the States of Output.

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.

Rung Rung is a simple line on which instruction are placed and logics are created.

E.g. here is an example of what one rung in a ladder logic program might look like. In real life,

there may be hundreds or thousands of rungs.

For example

1. ----[ ]---------|--[ ]--|------( )--

X | Y | S

| |

|--[ ]--|

Z

The above realises the function: S = X AND (Y OR Z)

Typically, complex ladder logic is 'read' left to right and top to bottom. As each of the lines (or

rungs) are evaluated the output coil of a rung may feed into the next stage of the ladder as an

input. In a complex system there will be many "rungs" on a ladder, which are numbered in order

of evaluation.

1. ----[ ]-----------|---[ ]---|----( )--

X | Y | S

| |

|---[ ]---|

Z

2. ---- [ ]----[ ] -------------------( )--

S X T

T = S AND X where S is equivalent to #1. above

This represents a slightly more complex system for rung 2. After the first line has been

evaluated, the output coil (S) is fed into rung 2, which is then evaluated and the output coil T

could be fed into an output device (buzzer, light etc..) or into rung 3 on the ladder. (Note that the

contact X on the 2nd rung serves no useful purpose, as X is already a 'AND' function of S from

the 1st rung.)

This system allows very complex logic designs to be broken down and evaluated.

More practical examples

Example-1

------[ ]--------------[ ]----------------O---

Key Switch 1 Key Switch 2 Door Motor

This circuit shows two key switches that security guards might use to activate an electric motor

on a bank vault door. When the normally open contacts of both switches close, electricity is able

to flow to the motor which opens the door. This is a logical AND.

Example-2

Often we have a little green "start" button to turn on a motor, and we want to turn it off with a

big red "Stop" button.

--+----[ ]--+----[\]----( )---

| start | stop run

| |

+----[ ]--+

run

-------[ ]--------------( )---

run motor

Example With PLC

Consider the following circuit and PLC program:

-------[ ]--------------( )---

run motor

When the pushbutton switch is unactuated (unpressed), no power is sent to the X1 input of the

PLC. Following the program, which shows a normally-open X1 contact in series with a Y1 coil,

no "power" will be sent to the Y1 coil. Thus, the PLC's Y1 output remains de-energized, and the

indicator lamp connected to it remains dark.

If the pushbutton switch is pressed, however, power will be sent to the PLC's X1 input. Any and

all X1 contacts appearing in the program will assume the actuated (non-normal) state, as though

they were relay contacts actuated by the energizing of a relay coil named "X1". In this case,

energizing the X1 input will cause the normally-open X1 contact will "close," sending "power"

to the Y1 coil. When the Y1coilof the program "energizes," the real Y1 output will become

energized, lighting up the lamp connected to it.

When the lamp is actuated

It must be understood that the X1 contact, Y1 coil, connecting wires, and "power" appearing in

the personal computer's display are all virtual. They do not exist as real electrical components.

They exist as commands in a computer program -- a piece of software only -- that just happens to

resemble a real relay schematic diagram.

Equally important to understand is that the personal computer used to display and edit the PLC's

program is not necessary for the PLC's continued operation. Once a program has been loaded to

the PLC from the personal computer, the personal computer may be unplugged from the PLC,

and the PLC will continue to follow the programmed commands. I include the personal computer

display in these illustrations for your sake only, in aiding to understand the relationship between

real-life conditions (switch closure and lamp status) and the program's status ("power" through

virtual contacts and virtual coils).

The true power and versatility of a PLC is revealed when we want to alter the behavior of a

control system. Since the PLC is a programmable device, we can alter its behavior by changing

the commands we give it, without having to reconfigure the electrical components connected to

it. For example, suppose we wanted to make this switch-and-lamp circuit function in an inverted

fashion: push the button to make the lamp turn off, and release it to make it turn on. The

"hardware" solution would require that a normally-closed pushbutton switch be substituted for

the normally-open switch currently in place. The "software" solution is much easier: just alter the

program so that contact X1 is normally-closed rather than normally-open.

CHAPTER – 4 SUPERVISORY CONTROL AND DATA

ACQUISITION SYSTEM

Introduction

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

control system: a computer system monitoring and controlling a process. The process can be

industrial, infrastructure or facility-based 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, 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.

What is Data Acquisition?

Data acquisition is the process of retrieving control information from the equipment which is out

of order or may lead to some problem or when decisions are need to be taken according to the

situation in the equipment. So this acquisition is done by continuous monitoring of the

equipment to which it is employed. The data accessed are then forwarded onto a telemetry

system ready for transfer to the different sites. They can be analog and digital information

gathered by sensors, such as flow meter, ammeter, etc. It can also be data to control equipment

such as actuators, relays, valves, motors, etc.

Vendors of SCADA:

Wonder ware – In Touch

Siemens – WinCc

Rockwell (Allen Bradley) – RS view

GE Fanuc – Cimplicity

Schneider – VG-look, VG-citect

Modicon – Moviecon

Intelluation – I-fix

KPIT – Astra

Here we will work on In Touch 7.0(Wonderware)

Why and where we use SCADA?

SCADA can be used to monitor and control plant or equipment. The control may be automatic,

or initiated by operator commands. The data acquisition is accomplished firstly by the RTU's

(remote Terminal Units) scanning the field inputs connected to the RTU (RTU’s may also be

called a PLC - programmable logic controller). This is usually at a fast rate. The central host will

scan the RTU's (usually at a slower rate.) The data is processed to detect alarm conditions, and if

an alarm is present, it will be displayed on special alarm lists. Data can be of three main types.

Analogue data (i.e. real numbers) will be trended (i.e. placed in graphs). Digital data (on/off)

may have alarms attached to one state or the other. Pulse data (e.g. counting revolutions of a

meter) is normally accumulated or counted.

These systems are used not only in industrial processes. For example, Manufacturing, steel

making, power generation both in conventional, nuclear and its distribution, chemistry, but also

in some experimental facilities such as laboratories research, testing and evaluation centers,

nuclear fusion. The size of such plants can range from as few as 10 to several 10 thousands

input/output (I/O) channels. However, SCADA systems evolve rapidly and are now penetrating

the market of plants with a number of I/O channels of several 100K.

The primary interface to the operator is a graphical display (mimic) usually via a PC

Screen which shows a representation of the plant or equipment in graphical form. Live data is

shown as graphical shapes (foreground) over a static background. As the data changes in the

field, the foreground is updated. E.g. a valve may be shown as open or closed. Analog data can

be shown either as a number, or graphically. The system may have many such displays, and the

operator can select from the relevant ones at any time.

SCADA systems were first used in the 1960s.SCADA systems have made substantial

progress over the recent years in terms of functionality, scalability, performance and openness

such that they are an alternative to in house development even for very demanding and complex

control systems as those of physics experiments. SCADA systems used to run on DOS, VMS

and UNIX; in recent years all SCADA vendors have moved to NT and some also to Linux.

Common system components

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 and sending

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 are more

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

Communication infrastructure connecting the supervisory system to the Remote Terminal

Units.

Supervision vs. control

There is, in several industries, considerable confusion over the differences between SCADA

systems and Distributed control systems (DCS). Generally speaking, a SCADA system usually

refers to a system that coordinates, but does not control processes in real time. The discussion on

real-time control is muddied somewhat by newer telecommunications technology, enabling

reliable, low latency, high speed communications over wide areas. Most differences between

SCADA and DCS are culturally determined and can usually be ignored. As communication

infrastructures with higher capacity become available, the difference between SCADA and DCS

will fade.

Architecture

In this section we are going to details which describe the common architecture required

for the SCADA products.

Hardware Architecture

The basic hardware of the SCADA system is distinguished into two basic layers: the

"client layer" which caters for the man machine interaction and the "data server layer" which

handles most of the process data control activities. The data servers communicate with devices in

the field through process controllers. Process controllers, e.g. PLC’s, are connected to the data

servers either directly or via networks or fieldbuses that are proprietary (e.g. Siemens H1), or

non-proprietary (e.g. Profibus). Data servers are connected to each other and to client stations via

an Ethernet LAN. Fig.1. shows typical hardware architecture.

Figure 1: Typical Hardware Architecture

Communication

Internal Communication:

Server-client and server-server communication is in general on a publish-subscribe and

event-driven basis and uses a TCP/IP protocol, i.e., a client application subscribes to a parameter

which is owned by a particular server application and only changes to that parameter are then

communicated to the client application.

Access to Devices:

The data servers poll the controllers at a user defined polling rate. The polling rate may

be different for different parameters. The controllers pass the requested parameters to the data

servers. Time stamping of the process parameters is typically performed in the controllers and

this time-stamp is taken over by the data server. If the controller and communication protocol

used support unsolicited data transfer then the products will support this too.

The products provide communication drivers for most of the common PLCs and widely

used field-buses, e.g., Modbus. Of the three fieldbuses that are recommended are, both Profibus

and Worldfip are supported but CANbus often not. Some of the drivers are based on third party

products (e.g., Applicom cards) and therefore have additional cost associated with them. VME

on the other hand is generally not supported.

A single data server can support multiple communications protocols; it can generally

support as many such protocols as it has slots for interface cards. The effort required to develop

new drivers is typically in the range of 2-6 weeks depending on the complexity and similarity

with existing drivers, and a driver development tool kit is provided for this.

Interfacing

Application Interfaces / Openness

The provision of OPC client functionality for SCADA to access devices in an open and

standard manner is developing. There still seems to be a lack of devices/controllers, which

provide OPC server software, but this improves rapidly as most of the producers of controllers

are actively involved in the development of this standard.

The products also provide

an Open Data Base Connectivity (ODBC) interface to the data in the archive/logs, but not

to the configuration database,

an ASCII import/export facility for configuration data,

a library of APIs supporting C, C++, and Visual Basic (VB) to access data in the RTDB,

logs and archive. The API often does not provide access to the product's internal features

such as alarm handling, reporting, trending, etc.

The PC products provide support for the Microsoft standards such as Dynamic Data

Exchange (DDE) which allows e.g. to visualize data dynamically in an EXCEL spreadsheet,

Dynamic Link Library (DLL) and Object Linking and Embedding (OLE).

Database

The configuration data are stored in a database that is logically centralized but physically

distributed and that is generally of a proprietary format. For performance reasons, the RTDB

resides in the memory of the servers and is also of proprietary format. The archive and logging

format is usually also proprietary for performance reasons, but some products do support logging

to a Relational Data Base Management System (RDBMS) at a slower rate either directly or via

an ODBC interface.

Scalability

Scalability is understood as the possibility to extend the SCADA based control system by

adding more process variables, more specialized servers (e.g. for alarm handling) or more

clients. The products achieve scalability by having multiple data servers connected to multiple

controllers. Each data server has its own configuration database and RTDB and is responsible for

the handling of a sub-set of the process variables (acquisition, alarm handling, archiving).

SCADA as a System

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 and sending

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 are more

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

Communication infrastructure connecting the supervisory system to the Remote

Terminal Units.

TYPICAL SCADA SYSTEM

System Concept

The term SCADA usually refers to centralized systems which monitor and control entire sites, or

complexes of systems spread out over large areas (anything between an industrial plant and a

country). Most control actions are performed automatically by remote terminal units ("RTUs") or

by programmable logic controllers ("PLCs"). Host control functions are usually restricted to

basic overriding or supervisory level intervention. For example, a PLC may control the flow of

cooling water through part of an industrial process, but the SCADA system may allow operators

to change the set points for the flow and enable alarm conditions, such as loss of flow and high

temperature, to be displayed and recorded. The feedback control loop passes through the RTU or

PLC, while the SCADA system monitors the overall performance of the loop.

Data acquisition begins at the RTU or PLC level and includes meter readings and equipment

status reports that are communicated to SCADA as required. Data is then compiled and

formatted in such a way that a control room operator using the HMI can make supervisory

decisions to adjust or override normal RTU (PLC) controls.

SCADA systems typically implement a distributed database, commonly referred to as a tag

database, which contains data elements called tags or points. A point represents a single input or

output value monitored or controlled by the system. Points can be either "hard" or "soft". A hard

point represents an actual input or output within the system, while a soft point results from logic

and math operations applied to other points. (Most implementations conceptually remove the

distinction by making every property a "soft" point expression, which may, in the simplest case,

equal a single hard point.) Points are normally stored as value-timestamp pairs: a value and the

timestamp when it was recorded or calculated. A series of value-timestamp pairs gives the

history of that point. It's also common to store additional metadata with tags, such as the path to

a field device or PLC register, design time comments, and alarm information.

Functionality

Access Control

Users are allocated to groups, which have defined read/write access privileges to the

process parameters in the system and often also to specific product functionality.

MMI

The products support multiple screens, which can contain combinations of synoptic

diagrams and text. They also support the concept of a "generic" graphical object with links to

process variables. These objects can be "dragged and dropped" from a library and included into a

synoptic diagram. Most of the SCADA products that were evaluated decompose the process in

"atomic" parameters (e.g. a power supply current, its maximum value, its on/off status, etc.) to

which a Tag-name is associated. The Tag-names used to link graphical objects to devices can be

edited as required. The products include a library of standard graphical symbols, many of which

would however not be applicable to the type of applications encountered in the experimental

physics community. Standard windows editing facilities are provided: zooming, re-sizing,

scrolling... On-line configuration and customization of the MMI is possible for users with the

appropriate privileges. Links can be created between display pages to navigate from one view to

another.

Trending

The products all provide trending facilities and one can summarize the common

capabilities as follows:

the parameters to be trended in a specific chart can be predefined or defined on-line

a chart may contain more than 8 trended parameters or pens and an unlimited number of

charts can be displayed (restricted only by the readability)

real-time and historical trending are possible, although generally not in the same chart

historical trending is possible for any archived parameter

zooming and scrolling functions are provided

parameter values at the cursor position can be displayed

The trending feature is either provided as a separate module or as a graphical object

(ActiveX), which can then be embedded into a synoptic display. XY and other statistical analysis

plots are generally not provided.

Alarm Handling

Alarm handling is based on limit and status checking and performed in the data servers.

More complicated expressions (using arithmetic or logical expressions) can be developed by

creating derived parameters on which status or limit checking is then performed. The alarms are

logically handled centrally, i.e., the information only exists in one place and all users see the

same status (e.g., the acknowledgement), and multiple alarm priority levels (in general many

more than 3 such levels) are supported.

It is generally possible to group alarms and to handle these as an entity (typically filtering

on group or acknowledgement of all alarms in a group). Furthermore, it is possible to suppress

alarms either individually or as a complete group. The filtering of alarms seen on the alarm page

or when viewing the alarm log is also possible at least on priority, time and group. However,

relationships between alarms cannot generally be defined in a straightforward manner. E-mails

can be generated or predefined actions automatically executed in response to alarm conditions.

Automation

The majority of the products allow actions to be automatically triggered by events. A

scripting language provided by the SCADA products allows these actions to be defined. In

general, one can load a particular display, send an Email, run a user defined application or script

and write to the RTDB.

The concept of recipes is supported, whereby a particular system configuration can be

saved to a file and then re-loaded at a later date. Sequencing is also supported whereby, as the

name indicates, it is possible to execute a more complex sequence of actions on one or more

devices. Sequences may also react to external events. Some of the products do support an expert

system but none has the concept of a Finite State Machine (FSM).

Features of SCADA

Dynamic Process Graphic mimics developed in SCADA software should resemble the process

mimic. SCADA should have good library of symbols so that you can develop the mimic as per

requirement. Once the operator sees the screen he should know what is going on in the plant.

Real Time and Historical Trend the trend play very important role in the process operation. If

your batch fails or the plant trips, you can simply go to the historical trend data and do the

analysis. You can have better look of the parameters through the trend. Ex. We commission a

SCADA system for Acid Regeneration plant where the plant has to be operated on 850-deg

temperature. If the operator operates the plant at 900 deg you can imagine how much additional

LPG he is putting into the reactor. Again what will happen to the bricks of the reactor? So the

production manger’s first job will be to go through the trends how the operators are operating the

plant. Even when the plant trips there are more than 25 probable reasons for the sample but if

you go through the history trends, it’s very easy to identify the problem.

Alarms have a very critical role in automation. Generally you have alarm states for each

inputs/outputs like your temperature should not cross 80 deg or lever should be less than 60. So

if the parameters go in alarm state the operator should be intimated with alarm. Most of the

SCADA software support four types of alarms like LOLO,LO,HI and HIHI. Deadband the value

of deadband defines the range after which a high low alarm condition returns to normal.

Alarms are the most important part of the plant control applications because the operator must

know instantly when something goes wrong. It is often equally important to have a record of

alarms and whether an alarm was acknowledged. An alarm occurs when something goes wrong.

It can signal that a device or process has ceased operating within acceptable, predefined limits or

it can indicate breakdown, wear or process malfunction.

Recipe Management is an additional feature. Some SCADA software support it, some do not.

Most of the plants are manufacturing multi products. When you have different products to

manufacture, you just have to load the recipe of the particular product.

Security is on facility people generally look for. You can allocate certain facilities or features to

the operator, process people, engineering dept and maintenance dept. for example operators

should only operate the system, he should not be able change the application. The engineers

should have access to changing the application. The engineers should have access to changing

the application developed.

Device Connectivity you will find there are hundreds of automation hardware manufacturer like

Modicon, Siemens, Allenbradley, ABB. Everybody has there own way of communication or we

can say they have their own communication protocol. SCADA software should have

connectivity to the different hardware used in automation. It should not happen that for Modicon

I am buying one software and for Siemens another one. The software like Aspic or Wonderware

has connectivity to almost all hardware used in automation.

Database Connectivity now a day’s information plays very important role in any business. Most

manufacturing units go for Enterprise Resource Planning or Management Information System.

Uses of SCADA

Production Department

● Real time production status: manufacturing status is updated in real time in direct

communication to operator and control device

● Production schedules: production schedules can be viewed and updated directly

● Production information management: production specific information is distributed to all

Quality Department

● Data integrity and quality control is improved by using a common interface

● It is an open platform for statistical analysis

● Consolidation of manufacturing and lab data

Maintenance Department

● Improved troubleshooting and de-bugging: direct connection to wide variety of devices,

displays improves troubleshooting reduces diagnostic/debugging time

● Plant can be viewed remotely. Notification can include pagers, e-mails and phones.

● Co-ordination between maintenance and management reduces unscheduled downtime.

Enterprise Information

● corporate information and real time production data can be gathered and viewed from

anywhere within operations

● User specific information ensures better informed decisions

● Data exchange with standard databases and enterprise systems provides integrated information

solutions

Engineering Department

● Integrated automation solutions reduce design and configuration time

● Common configuration platform offers flexibility for constant configuration in all areas

● Capable of connecting to wide variety of systems. Reduces start up time and system training

with industry proven open interfaces

Manufacturing Department

● Unscheduled down time is reduced due to swift alarm detection and event driven information

● Makes operations easier and more repeatable with its real time functionality

● Secured real time operation are maintained with windows

General Terminology

What is a Tag- a tag is a logical name for a variable in a device or local memory (RAM). Tags

that receive data from some external devices such as programmable logic controllers or servers

are refereed to as I/O tags. Tags that receive data internally from software are called memory

tags.

Analog Tags- store a range of values. EX temp, flow, density etc

Discrete tags- to store values such as 0 or 1. EX on/off status of a pump, valves, switches

etc.

System tags- store information generated while the software is running including alarm

info and system time and date.

String tags- are used to store ASCII strings a series of characters or whole word. The

max string length is 131 characters.

Touch links- allow the operator to input data into the system. EX. Operator may turn the value

on or off, enter a new alarm set point, run a complex logic script etc.

Touch push buttons-are used to create object link that immediately perform an operation when

clicked with the mouse or touched. These operations can be discrete value changes, action script

executions and show or hide window commands.

Colour links- are used to animate the line colour, fill colour or text colour of an object. Each of

these colour attributes can be made dynamic by defining a colour link for the attribute. The

colour attribute may be linked to the value of a discrete expression, analogue expression, discrete

alarm status or analog alarm status.

Visibility- used to control visibility of an object based on the value of discrete tag name or

expression.

Blink- used to make an object blink based on the value of the discrete tagname or expression.

Orientation- used to make an object rotate based on the value of a tagname /expression.

Disable- used to disable the touch functionality of objects based on the value of a tagname of

expression. Often used as a part of a security strategy.

Value display links- provides the ability to use text object to display the value of a discrete,

analog or string tagname.

Percent fill links- used to provide ability to vary the fill level of a filled shape according to the

value of an analog tagname or an expression that computes to an analog value.

Application script- are linked to entire applications and are used to start other applications,

create process simulation, calculate variables and so on: three types of application scripts are on

start up, while running, on shut down.

Window script- is linked to specific window. 3 types of window scripts are on show, while

showing, on hide.

Key script- touch pushbutton action scripts are similar to key scripts, except they are associated

with an object that you link to a touch link action pushbutton. 3 types are on key down, while

down, on key up.

Condition script- is linked to discrete tagname or expression that equates to true or false. You

can also use discrete expressions that contain analog tagnames. 4 types of scripts that you can

apply to a condition are on true, on false, while true, while false.

Data change script- are linked to a tagname and/or tagname field changes by a value greater

than a dead band that you defined for the tagname in the tagname dictionary.

Application security- to an application is optional. It provides the application developer with the

ability to control whether or not specific operators are allowed to perform specific functions

within an application Security is based on the concept of operator logging on to the application

and entering his user name and password and access level. For each operator access to any

protected function is granted upon verification of his password and access level.

Security Issues

The move from proprietary technologies to more standardized and open solutions together with

the increased number of connections between SCADA systems and office networks and the

Internet has made them more vulnerable to attacks. Consequently, the security of SCADA-based

systems has come into question as they are increasingly seen as extremely vulnerable to cyber

warfare/cyber terrorism attacks.

In particular, security researchers are concerned about:

the lack of concern about security and authentication in the design, deployment and

operation of existing SCADA networks

the mistaken belief that SCADA systems have the benefit of security through obscurity

through the use of specialized protocols and proprietary interfaces

the mistaken belief that SCADA networks are secure because they are purportedly

physically secured

the mistaken belief that SCADA networks are secure because they are supposedly

disconnected from the Internet

SCADA systems are used to control and monitor physical processes, examples of which are

transmission of electricity, transportation of gas and oil in pipelines, water distribution, traffic

lights, and other systems used as the basis of modern society. The security of these SCADA

systems is important because compromise or destruction of these systems would impact multiple

areas of society far removed from the original compromise. For example, a blackout caused by a

compromised electrical SCADA system would cause financial losses to all the customers that

received electricity from that source. How security will affect legacy SCADA and new

deployments remains to be seen.

Many vendors of SCADA and control products have begun to address these risks in a basic sense

by developing lines of specialized industrial firewall and VPN solutions for TCP/IP-based

SCADA networks. Additionally, application white listing solutions are being implemented

because of their ability to prevent malware and unauthorized application changes without the

performance impacts of traditional antivirus scans. Also, the ISA Security Compliance Institute

(ISCI) is emerging to formalize SCADA security testing starting as soon as 2009. ISCI is

conceptually similar to private testing and certification that has been performed by vendors since

2007. Eventually, standards being defined by ISA99 WG4 will supersede the initial industry

consortia efforts, but probably not before 2011.

The increased interest in SCADA vulnerabilities has resulted in vulnerability researchers

discovering vulnerabilities in commercial SCADA software and more general offensive SCADA

techniques presented to the general security community. In electric and gas utility SCADA

systems, the vulnerability of the large installed base of wired and wireless serial communications

links is addressed in some cases by applying bump-in-the-wire devices that employ

authentication and Advanced Encryption Standard encryption rather than replacing all existing

nodes.

SCADA as an asset

TYPICAL DETERIORATION CURVE FOR INFRASTRUCTURE ASSET

Practical Uses of SCADA

● SCADA used as a control mechanism for chemical plants, electricity generation, electric

power transmission, electricity distribution, district heating.

● Control mechanisms are described in Process Control.

●EPICS is an example of an open source software environment used to develop and implement

SCADA system to operate devices such as particle accelerators, telescopes and other large

experiments.

Advantages of SCADA System

1. A SCADA system is "normally" significantly cheaper than a DCS.

2. SCADA can continue operating even when telecommunication are temporarily lost.

3. SCADA systems allow a smaller number of operators to control a large number of

individual assets.

4. SCADA systems were designed to be used on large scale systems with remote assets

over a very large geographical area.

5. SCADA system improves operation, maintenance and customer service and provides

rapid response to emergencies.

6. It provides a high level of system reliability and availability.

Mid – Term ReportOn Behalf Of

6 Months Industrial TrainingAt

Prolific Systems and Automation Technology Pvt. Ltd. Noida

Submitted To: Submitted By:

Er. Krishan Arora Sourabh BansalLect. (EEE) B.Tech (EEE), 8th sem 6080709649