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1.0 INTRODUCTION
SCADA stands for supervisory control and data acquisition. It generally refers to
industrial control systems: computer systems that monitor and control industrial,
infrastructure, or facility-based processes, as described below:
Industrial processes include those of manufacturing, production, powergeneration, fabrication, and refining, and may run in continuous, batch, repetitive,
or discrete modes.
Infrastructure processes may be public or private, and include water treatment
and distribution, wastewater collection and treatment, oil and gas pipelines,
electrical power transmission and distribution, Wind farms, civil defense siren
systems, and large communication systems.
Facility processes occur both in public facilities and private ones, including
buildings, airports, ships, and space stations. They monitor and control HVAC,access, and energy consumption.
A SCADA System usually consists of the following subsystems:
A Human-Machine Interface or HMI is the apparatus which presents process data
to a human operator, and through this, the human operator monitors and controls
the process.
A supervisory (computer) system, gathering (acquiring) data on the process andsending commands (control) to the process.
Remote Terminal Units (RTUs) connecting to sensors in the process, converting
sensor signals to digital data and sending digital data to the supervisory system.
Programmable Logic Controller (PLCs) used as field devices because they aremore economical, versatile, flexible, and configurable than special-purpose RTUs.
Communication infrastructure connecting the supervisory system to the RemoteTerminal Units.
Industrial Use of SCADA System
This article describes the function of SCADA, its application in oil and gas
flowing, waste water management, power and electricity surges.
WHAT IS SCADA AND ITS NEED?SUPERVISORY CONTROL AND DATA ACQUISITION
We more frequently call it as SCADA. As the name implies SCADA system
supervises, acquires and control data received from a distant data source from the
control center. SCADA system is located in the control center and is operated in
the scanning mode, communicating between the CONTROL CENTER and the
REMOTE STATION by means of two-way communication channels. Such a
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supervisory control and data acquisition system is intended to facilitate the work of
operator by acquiring and compiling information as well as locating, identifying
and reporting faults. On the basis of information received, the operator makes
necessary decisions via the control system he can then perform different control
operations in power stations or influence the processing of the information
acquired. The main task of a modern day power system is to ensure quality and
reliable power at an economic rate. Hence the system is to be updated at a very fast
rate (real time
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Mode/management), which helps to control the complex system effectively
without any loss of time.
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A BRIEF HISTORICAL PERSPECTIVE
Telemetry systems were initially developed in the 1960s for remote monitoring and
control of geographically distributed critical infrastructure such as railroads; gas
and liquid pipelines; electric power transmission and distribution systems; andwater/wastewater systems. Prior to the introduction of supervisory control and data
acquisition (SCADA) technology these facilities used a variety of telemetry
schemes, the most popular of which was frequency division multiplexing (FDM or
Tone) telemetry. Telemetry has always involved electrical and electronicequipment, but prior to 1970, these were primarily hardwired architectures using
relatively simplistic communications schemes.
SCADA systems are based on the use of a central computer to communicate with
remote data acquisition and control equipment. A significant reason for the growth
and proliferation of SCADA technology in the 1960s and early 1970s was the
introduction of lower-cost computing platforms (i.e., 8- and 16-bit minicomputers)
during that same period. SCADA systems prior to the development of
minicomputers were built around large, expensive mainframe computers. As such,
they were relegated to only the most critical applications that could justify the
substantial expense. Electric utilities were among the first to make significant
investments in modern SCADA technology.
2.0 SCADA FUNDAMENTALS
With the advent of lower cost computer technology it became possible to usecomputers, and appropriate software, to perform the functions previously relegated
to the panel instruments and tone telemetry, and in particularly the electronic head-
end display technology. Computers could be programmed to communicate with
newly developed electronic field data acquisition and control units in the same
manner used by the earlier hardwired master station equipment.
2.1 Supervisory Control And Data Acquisition (SCADA) Systems
All supervisory control and data acquisition (SCADA) systems have several basic
components: a central computer (probably redundant), a human-machine interface,
electronic field terminal units (usually called RTUs) and some type ofcommunication infrastructure to connect the central computer with the field data
acquisition and control units. SCADA systems have evolved over time and have
architecturally followed the changes in computer and communications technology.
One of the primary technology drivers that pushed the development of SCADA
technology was the development of low-cost 8- and 16-bit computers called
minicomputers, the other being the development of the microprocessor several
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years later. The microprocessor advanced remote terminal unit (RTU) technology
in the 1970s in much the same way that minicomputers advanced the technology of
SCADA master stations in the 1960s.
Prior to the arrival of microprocessors, RTU equipment was hardwired for a
specific set of functions, a fixed quantity of I/O and a fixed-format digitalmessaging scheme. In the 1970s RTUs based on microprocessor technology were
introduced. These new intelligent RTUs could be programmed to perform newand more sophisticated functions, and could even be modified by the end user.
SCADA systems have steadily benefited by incorporating in advances in computer
technology throughout the past three decades.
SCADA systems are used to monitor and control geographically distributed
processes. This means that they allow the user of such a system to see what ishappening at the geographically distant locations and to effect a certain level of
control over the equipment/process at those locations.
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2.2 SCADA Master Station (Host) Computer Systems
The SCADA Host (orMaster Station) computer is the repository of the real-time
data that is collected from all of the various RTUs connected to it in any form.
Architecturally,Hostcomputer configurations have evolved through the years and
have done so because of changes in computer technology. Very few SCADAsystem suppliers have actually designed and built their own computer equipment.
Although a couple of computer manufacturers (notably IBM and CDC) developed
relatively short-lived SCADA systems, most are compelled to create mission-
critical SCADA systems using commercial off-the-shelf (COTS) computing
technology.
The SCADA host must have software to continuously send polling messages to all
of the RTUs, using the designated protocol, and must also be able to retrieve,
process and store the information returned from the various RTUs. This generally
means that there is some form of table internal to the host that contains the mostrecent values from all of the RTUs. In many cases, this RTU data may be in raw
counts and must therefore be converted to relevant engineering units by the host.
This also means that a set of numeric values (the m and b quantities in the
equation y=mx+b) associated with each incoming data value, which define the
linear conversion calculation must also be accessible. Finally, there needs to be a
way to reference each incoming value. Referring to a signal as the twelfth analog
input from the RTU with address 4 on the 6th
polling channel, though rather
clumsy for practical use, is actually how the computer finds that particular value.
Thus, all SCADA systems feature some sort of naming scheme whereby a tagname (e.g., LAK-T202-TTT) can be associated with each input and output.
2.3 Remote Terminal Units (RTUs)
An RTU is an electronic device that has special circuitry allowing it to interface
with process instrumentation and control equipment. Physical parameters such as
pressure, flow, temperature, etc. are measured by special sensory devices that
generate an electrical signal corresponding to the parameter value. Some
measurements only have two values or states (such as is a motor on or off, is a
valve open or closed, etc.) These can be electrically represented with a simple
contact (switch) signal. The RTU has electronic input and output circuitry thatpermits the RTU to measure and generate these electrical and contact signals.This is generally referred to as I/O (input/output) circuitry.
There are two categories of such I/O hardware: analog and digital. Analogcorresponds to measurements that have a numeric range (e.g.50 to 200 C)
represented by a voltage signal over a corresponding range (e.g.10 volts to +10volts.) The I/O section of the RTU uses a circuit called an analog-to-digital
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converter (ADC) to generate a numeric value from the voltage input signal.
Digital corresponds to measurements that have a limited number of states (most
often two) that can be represented by the state of a contact. This I/O section uses
circuitry to sense the state of the contact and generates a binary flag that
corresponds to the state.
Since the RTU (at least today) is a microprocessor-based device, such values and
measurements are represented internally (within the microprocessor of the RTU) as
binary numbers or discrete bits. Usually an ADC generates a fixed sized binary
value (12, 14 and 16 bit values are typical.) In a similar manner, the output portion
of the I/O circuitry allows the RTU to generate a voltage signal or a contact signal
that can be used to control process equipment (such as starting a motor or adjusting
the position of a valve.)
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The basic job of the RTU is to scan through all of the signals wired to its inputs
and record their values, and then to repeat this process over and over again so that
it always has the current values. These values can then be sent to the SCADA
central computer and presented to the human that is monitoring the process. In a
basic RTU these values will be represented as raw counts and binary flag bits.Therefore, a field measurement value of -20C to 150C might be represented by a
binary count in a numeric range of 0000 to 8191 (01FFF hexadecimal, a 12 bit
value). Obviously, these raw counts need to be converted into the proper
measurement value (typically called the engineering units value) beforepresentation to a human operator. In a SCADA system this can be done either
within the RTU, or at the central computer, depending on the capabilities of the
RTU.
The original non-microprocessor-based RTUs had no arithmetic or computational
capability and so they only provided raw count values. Thus, all early SCADAsystems did the conversion to engineering units in the central computer (and the
communication scheme and message formats used, were based on transmission of
raw count values.) More recently, based on microprocessor-based RTU
technology, there have been systems where value conversion (and even alarm
checking) has been accomplished within the RTU.
One reason for this has been the implementation of control and calculation logic
within the RTU, and even local operator displays, and thus the need for
engineering units. In a much simpler manner, binary/status inputs also can beconverted to engineering units. This involves providing a text description for the
binary states. Thus, rather than indicating the status of a pump as 1 you wouldsubstitute the text string RUNNING. In the same manner you would provide
STOPPED rather than 0 for the alternate state. This evolutionary step, of doing
value conversion within the RTU, has been most prevalent in the pipeline industry
and somewhat less in the water/waste-water industry. It has not been a technology
trend in the electric utility industry.
2.4 RTU Technology Advancements
As RTUs became smart through the application of microprocessor technology,
they began to provide a platform for adding increasing functionality. Because they
could be (re)programmed it was possible to make continuous enhancements (orcorrect bugs) simply by changing the programming. As new functions wereadded, the digital communications messaging scheme (commonly called a
protocol) could also be modified to support these new functions and features.
Of course, this also made it more difficult to maintain compatibility with SCADA
systems and product families. But, the new features and functions were compelling
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and so vendors and customers put up with the problems. Every SCADA vendor
was originally in the business of building their own, proprietary RTUs, and
inventing their own communication protocols. Eventually (in the mid to late
1990s) a few protocols became dominant and de facto standards to which most
vendors eventually conformed. These de facto standards vary by industry segment
and in some cases dont support all/any of the more advanced functions typically
supported by a given vendors proprietary protocol (e.g., it may be possible toconfigure and download new RTU software using the vendors proprietary
protocol, but not using a standard protocol.)
As previously mentioned, the basic function of an RTU is to scan and process
inputs and provide them to the SCADA central computer (also called the host)when requested, using a digital communication messaging scheme (a protocol.)The second part of this base functionality is the ability of the host to send protocol
messages to the RTU that cause it to manipulate its output
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values. This may mean adjusting a voltage output that is controlling a pumpsspeed, or closing a contact that stops a motor. In a basic RTU the outputs are
ONLY manipulated at the request of (receiving the correct messages from) the host
computer. These two components: scanning inputs and manipulating outputs,
comprise the basic aspects of supervisory control.2.5 SCADA Communications
The RTU needs to be able to send its data to the host computer for presentation to
the user of the SCADA system, and needs to receive control command messages.
This means that there has to be some form of communications system to transport
the protocol messages between the host and the various RTUs. Since, by nature,
SCADA systems tend to encompass a large geography with RTUs situated
throughout the area, the communications technology employed must embrace this
architecture. Moreover, there are industry- and application-specific speed and
performance requirements related to the particular process dynamics of eachmarket.
Another key consideration is the availability (or sometimes, the unavailability) of
suitable commercial/public communications infrastructure. All of this must be
taken into account in designing a SCADA communications scheme.
Prior to the development of computer networking the vast majority of
communications technologies for communicating over great distances, to a large
number of locations, were designed for voice communications among human
beings. These included radio, telephone, microwave and even satellite
communications systems. It is important to remember that the telephonecompany (Ma Bell) pioneered microwave, satellite, fiber-optic and cellulartelephone technologies as a means for providing voice telephone service.
By making use of this voice-based technology, SCADA systems were implicitly
restricted to the bandwidth limitations of such systems. Since a voice circuit carries
sound, the digital information being transmitted between RTUs and SCADA hosts
had to be converted into audio signals to make use of the then-available
communications networks. That meant the use of special circuitry to modulate and
de-modulate (a modem) the digital signal.
Early modems supported rather low data rates: 1200 and 2400 bits per second. This
limited data rate caused RTU/SCADA vendors to design their protocols to be as
efficient (and feature-poor) as possible, so that polling of an RTU would take as
little time as possible. Some of these communications schemes could be used in a
multi-drop or point-to-point configuration; others (e.g., radio) only in a multi-drop
arrangement.
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When a radio enabled SCADA host transmits a message on frequency X all ofthe RTUs hear it because they are all listening on frequency X. Only one RTU
can answer at a time or they will interfere with each other (like multiple students
answering the teachers question at the same time.) Thus, the host has to
interrogate each RTU in turn in order to collect all of their information. Adding
more RTUs extends the cycle time for each polling sequence. With a telephone
system, it would be possible (although more expensive) to have a separate phone
circuit to each RTU so that the host could communicate with multiple, or all, RTUs
concurrently.
A less costly alternative might to allow a few RTUs to be multi-dropped on each
circuit, thus minimizing the polling cycle time. With all RTU protocols that
support multi-dropping there is a method for identifying the particular RTU to
which the host message is directed. This is usually in the form of a unique number
or address that is part of the message. All RTUs on a shared (multi-dropped)
circuit hear the host messages, but only the RTU with a matching address numberwill respond to a given message. GITA CONFERENCE PROCEEDINGS Sunday,
April 23, 2006 (Tampa, Florida) ShawW.doc Page 6 of 10 6/8/2006
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In practice, the electric utility market has tended to use a dedicated leased
telephone circuit to each RTU, or have constructed their own telephone
infrastructure (using the same technology as the telephone company) to provide a
separate circuit to each RTU. This has allowed host data updates every 1 to 5
seconds, from ALL field sites, even at low data rates such as 1200/2400 bits persecond. Why would an electric utility choose to construct its own telephone
infrastructure? In many cases because their long-haul transmission systems were
out in wide-open areas where there was no telephone service. So they built their
own.
Another type of electric utility is the municipal electric utility, typically having a
more limited geographical service area than IOUs. These utilities have used leased
telephone circuits extensively and have recently begun creating their own fiber-
optic communications systems. Since much of a municipal electric utilitys servicemission is power distribution, there has also been widespread use of radio
communications for SCADA systems implemented for distribution automation and
distribution management purposes.
By contrast, many water/wastewater utilities have elected to use radio-based
communications systems for their SCADA applications. This is possible because in
most cases, the utility service area was large but geographically restricted to an
urban area, all within the distance limits of conventional radio (possibly with a few
repeaters). Also, this was often part of a system that the utility already owned and
operated for voice communications or other purposes.
Radio-based polling is generally a multi-dropped scheme, causing polling cycles
might require several minutes to complete. However, the process dynamics ofwater/wastewater systems are relatively slow and can tolerate fairly long periods
between host data updates of all but the most critical information. Many such
systems have been deployed using leased telephone circuits, but unlike electric
utilities, often with multiple RTUs per circuit. Some utilities have a mixture of
radios and leased circuits, sometimes with one as a backup to the other (e.g.,
switch to radio, and accept a performance reduction, if the telephone lines go
down.)
Pipeline applications, like electric power transmission systems, often require
communications over very long distances and extending into remote locationswhere no telecommunications infrastructure exists. Historically, pipeline
companies have generally constructed their own communications systems, initially
using microwave backbones and more recently switching to fiber-optic cables.
In the 1980s and 1990s, several pipeline SCADA systems made use of commercial
satellite technology and something called X.25 packet switching technology, which
pre-dates modern digital networking. In general most older pipeline SCADA
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systems have tended to be designed with a goal of full host data updates from all
RTU sites every 10 to 30 seconds.
Until fairly recently, when SCADA deployment involved building a private
telecommunications infrastructure, it was based on voice telephone technology and
thus often provided many more voice circuits than were needed for the SCADAproject. (In many cases, this excess circuit capacity was leased back to the local
telephone company to help underwrite some of the project expense.)
3.0 SCADA FUNCTIONALITY
A SCADA system might be continuously fetching and processing hundreds to
thousands of values, every polling cycle. There is no practical way for a human to
look at all of these values to see if they are within acceptable/expected bounds.
DATA ACQUSITION- Furnishes status information & measurands data to
operator
CONTROL - Allows the operator to control the devices e.g. ckt breakers, Xmer,
tap changer etc from a remote centralized location .
DATA PROCESSING - Includes data quality & integrity check , limit check ,
analog value processing etc.
TAGGING - Operator identifies any specific device & subjects to specific
operating restrictions to prevent from unauthorized operation
ALARMS - Alerts the operator of unplanned events & undesirable operating
conditions in the order their severity & criticalityLOGGING- Logs all operator entries, alarms &selected entries
TRENDING- Plots measurements on selected scale to give information on the
trends e.g. one minute, one hour etc.
3.1 FUNCTIONAL UNITS OF SCADA:
1. Data collection equipment.
2. Data transmission / telemetric equipment.
3. Remote terminal unit.4. Data loggers.
5. Data presentation equipments.
The figure shown below represents the simplest SCADA configuration employing
single computer; Computer receives data from RTUs via the communication
interface. Operators control base one or more CRT terminals for display. With
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Fig. 1: Simple SCADA system with single computer
terminal it is possible to execute supervisory control commands and request the
display of data in alpha numerical formats arranged by geographical location and
of type. The programming input/output is used for modifying the supervisory
software. In the basic SCADA system, all the programs and the data is stored in the
main memory. The more sophisticated version of SCADA has additional auxiliary
memories in the form of magnetic disc units.
As was mentioned, the purpose for doing alarm limit checking in the host was to
identify measurements (or computed values) that were deviating in a suspicious ordangerous manner. Once identified, aside from setting a flag in the real time table,
the SCADA system would bring the problem to the attention of the system user. In
older systems this was accomplished by typing a message on a printer designated
for alarming purposes. The system might also produce an audible alarm (to wake
up a dozing system operator.)
RTU RTU RTU
C. P. U.Prog. I/O
equipment
Auxiliary Memory
Communication
Interface
Display and
Control
Console
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In most SCADA systems another important function is to provide a means for
recording critical values over some time span back from the current time and date.
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A very essential feature of most SCADA systems today is their ability to generate
printed reports and logs. Hourly, shift, daily, weekly, monthly, quarterly and
annual reports need to be printed on a routine, scheduled basis. Others need to be
printed when specified trigger events take place.Older SCADA systems usually included a FORTRAN compiler that could be used
for report programming. Today, with the ubiquitous presence of Microsoft
software and spreadsheet tools, most SCADA systems offer those (with dll orodbc or plug-in connections to the real-time and historical data) for reportingpurposes.
3.2 AUTOMATIC SUB-STATION CONTROLThe electrical energy is transferred from large generating stations to distant load
centers via various sub-stations. In every sub-station certain supervision, controland protection functions are necessary. Every substation has a control room. The
relay and protection panels and control panels are installed in the control room.
The various circuit breakers, tap changers and other devices are controlled by
corresponding control-relay panels. In a small independent sub-station, the
supervision and operation for normal service can be carried out by the operator
with the aid of analogue and digital control systems in the plant. The breakers can
be operated by remote control from the control room. During faults and abnormal
conditions, the breakers are operated by protective relays automatically. Thus, the
primary control in sub-station is of two categories.1. Normal routine operation by operators command.
2. Automatic operation by action of protective relays and control systems.
3.3 SUB STATION CONTROL FUNCTION ARRANGED THROUGH
SCADA SYSTEM
1. Alarm FunctionsTo sound alarm/annunciation regarding dangerous, uncommon events such as
abnormal values of process parameters, fire, illegal entry in premises, overtemperatures, low voltage of auxiliary supply, unusual happening etc. Alarms are
obtained from data logger and are for alerting this operator in the control room.
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2. Control and IndicationControl of two position devices such as, circuit -breakers, isolators, earthing-
switches, starters. Indication of ON/OFF state of the devices on control
board/mimic diagrams.
Control of position of devices having positions (closed, middle open) e.g.
values, input settings, indication of position on control panels.
Control positions of multi-position device e.g. tap changer, indication of
position on control panels.
Indication without control.
Control without indication: e.g. raise or lower control of generator load by
automatic load frequency control.
Set-point control to provide set point to a controller located at remote sub -
station.
3. Data collection, recording, display.
4. Sequential operation of devices with predetermined time and conditions foroperation of various devicese.g.
Auto-reclosing of circuit-breakers operation O-CO-Time-CO
Operation of circuit-breaker, isolator and earthing-switch in a particular
sequence during opening of circuit and another sequence during closing of circuit.
5. By means of SCADA system, the operator in control centre can cause
operations in a remote sub-station. The possible remote operations include:Opening and closing of switching devices I
Tap-changing of transformers (voltage control)
switching of capacitor banks (voltage control)
Load shedding (load frequency control)
6. Some of the remote operations are made automatic by one -line computer
based system without human intervention e.g. Net work islanding, Backup
protection. The automatic control function are segregated into :Interconnection functions
Transmission line automatic function
Distribution system automatic functions
3.4 Advantages of SCADA system:1. Flexible, simple, reliable.
2. Efficient with less manpower.
3. Security.
4. Self-checking and readability.
5. Portable and cost efficient.
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3.5 Applications of SCADA system:1. Inside power plant.
2. On power plant.
3. Industrial establishment.
4. Load dispatch center.
5. Railways.
TWO-WAY COMMUNICATION CHANNELS BETWEEN THE MASTER
CONTROL CENTRE AND REMOTE CONTROL CENTRE
SCADA
Traditionally, the SCADA systems were used for scanning mode, providing data
regarding generating stations, generating units, transformer sub-stations etc.
SCADA systems were arranged to perform several functions to supplementAutomatic Control and Protection Systems.
Now a days protective relays, control relays and control systems are used for
automatic control of generating stations and transmission systems along with
SCADA. Only initiating devices may be different or omitted with fully automatic
SCADA control. For example, tap changing may be initiated either by the sub-
Station Check
Trip-Close
Lower-Raise
Close-OpenStop-Start
Analog DataCounted Data
Binary Data
Alarms & Status
Indication
M
o
d
e
m
M
o
d
e
m
Remote
station
Master
Session
Data Display
Alarm
Annunciation
Indication
Special
Function
A/D Converter
Pulse Counter
Binary Data
Indication
Analog Data
ControlControl &
Indication
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section control room operator or by the automatic voltage control relays connected
in the protection panel of the transformer.
Controls systems were arranged to keep the values of controlled quantities within
target limits. Protection equipments were arranged for sounding alarms and for
tripping circuit -breakers.
With the recent revolution in microprocessor technology, the size, performance
and cost of digital automation systems have become acceptable in commercial
installation. SCADA provides integrated approach to power system protection,
operation control and monitoring, automatically with least intervention of the
control room operator.
The microprocessors located in the master station, generating stations, transmission
sub - stations and distribution sub-stations provide control and protection decisions
locally where the data is located. The action is reported to the operator "by
exception". The operator retains the option of taking intervening action of
overriding or initiating of his own. All these microprocessor based systems areconnected through the GLOBAL POSITIONING SYSTEM. The functions and
architecture of SCADA system is selected in accordance with the functional
requirements and size of the power system.
4.0 FEATURES OF SCADA
Tracker Option: This feature provides collection and storage of variety
pertaining to the serialized items such as time stamps, quality measurements,
temperature, humidity, pressure, sub- assembly part number etc through variousautomated sensors and readers like bar code readers, radio frequency tags, and
mechanical tag based system. This information is used for over viewing the flow of
serialized items and the location of materials through the system which helps in
isolating the defective items from the perfect ones. For example boxes or
containers over a specified weight limit may be routed to different storage area
Data import/export function: This feature allows the transfer of all point
configuration data via a comma separated variable file. Points are therepresentation of actual field parameters; these are the variables in which the actual
incoming data is stored. Similarly point configuration can be sent to other SCADA
system for their use over there. This is made possible through data import/exportfacility. Data management is possible using MS EXCEL,
MS ACCESS etc.
Flexibility: This feature provides tools by which an existing system could be
tailored according to the changes taking place. Thus the user can mould the system
according to the demands thus making it more flexible.
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Forecasting: Forecasting is the ability to predict future state of the system by
studying previously collected data. Forecasting feature of SCADA system allows
the operator to visualize the state of the system well in advance, hence the operator
has enough time to manage the system properly. This feature of SCADA finds a
huge application in Energy Management System.
Job Management: Using SCADA all the tasks can be properly sequenced and
executed to allow the most efficient task scheduling for proper utilization of man
and machinery of plant.
4.1 SECURITY OF SYSTEM OFFERED BY SCADAIn the age of automated systems, security, reliability and availability of data is top
priority of any computer based automated system. Small loss of data in such
system can cause havoc and may bring a system to a standstill.
SCADA ensures a high degree ofsecurity. Security of any process may be definedas the ability of the system to operate in normal state even with the occurrence of
specified contingencies.
The system shall by all means remain in the state of normal operation by means of
fast acting control systems following a contingency and without having a system to
go into an emergency state. Continuous monitoring of security and appropriate
corrective action for improving security is called security control. System security
analysis is generally broken down into following three functions:
System monitoring: SCADA provides up to date information regarding the
condition of the processes.
Contingency analysis: Sometimes abnormalities give the operator very less time
to react. SCADA system provides contingency analysis, which consists of action to
be taken by the operator in advance. Thus it allows the system to operate
defensively.
Corrective action analysis: It allows the operator to take appropriate corrective
action in the event of contingency in order to ensure the smooth functioning of the
process.
5.0 CONCLUSIONFrom the above paper we can summarize that the SCADA supplements the control
and protection system to form an integrated system, which is compact, economical
and versatile. In short we can say that it acts under the GLOBALPOSITIONING SYSTEM, so that whole system works in same time domain.
Today the buzzword in any industry is Optimal Performance at MaximumEconomy.
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SCADA has provided the industry with the perfect Man Machine Interfacewhich has solved many or to be precise, most of the problems related to
monitoring, supervision, data acquisition and controlling. The most significant
contribution of SCADA is probably having an easy -to-use graphical interface,
which has made the tedious job of operators very easy. SCADA has manifold
applications like Distribution Management, Energy Management, Power Plant
Management & Oil and Gas Distribution System. SCADA has also enabled Grid
monitoring by virtue of which power can by shared on national basis. So the
bottom line is that SCADA is a boon to Indian powersector.
REFERENCES1. Sunil S. Rao, Switchgear Protection and Power Systems
2. A.K. Sawhney, Electrical Measurements & Measuring Instruments3. The Information Digest On EnergyVol -2 March1992.
4. Tery News WireVolII Jan1996 - Dec1996.5. Tery Energy Environment Monitor- Vol-I March-1996.
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