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SCADA

(SUPERVISORY CONTROL AND DATA ACQUISITION)

By:

A RAKESH(05671A0232)

EEE IV/IV

Email: rakesh.sri.adepu@gmail.com

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INTRODUCTION:-

SCADA stands for SUPERVISORY CONTROL AND DATA

ACQUISITION

Primary function -data acquisitionfrom data flds called RTU(remote

terminal unit)

RTU scans analog data like current, vtg, active, reactive, apparent power,

frequency, digital data of breakers

It is used in industrial m/m and control s/m consisting of a central host

master(MTU)

s/m similar to scada s/m are routinely seen in factories, treatment plantsReferred to distributed control systems(DCS)

RTu communication may be via LOCAL AREA NETWORK(LAN)

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HISTORY:

it is not an fully control s/m but it focuses on supervisory level

It takes several i/p o/p channels

SCADA s/m used to runs on DOS, VMS & UNIX

Pvss as one of the SCADA products for the development of future

control systems at CERN in On 20 Sept. 2000, the Finance Committee

approved the proposal to negotiate a contract with ETM A.G

SCADA systems have made substantial progress over the recent

years in terms of functionality, scalability,

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SCADA architecture:

SCADA developoed in morden technologies in three generations

First Generation Monolithic Second Generation Distributed

Third Generation Networked

MONOL ITHIC SCADA SYSTEMS:SCADA systems were first developed - computing in general centered on

mainframe systems.

SCADA systems were standalone systems with virtually no connectivity to other

systems.

The Wide Area Networks (WANs) that were implemented to communicate with

remote terminal units (RTUs)

single purpose in mindthat of communicating with RTUs in the field and nothing

else

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The communication protocols in use on SCADA networks were developed by vendors

of RTU equipment

. Redundancy in these first generation systems was accomplished by the use of two

identically equipped mainframe systems,

a primary and a backup, connected at the bus level.

The standby systems primary function -monitor the primary and take over in the event

of a detected failure

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The next generation of SCADA systems took advantage of

developments and improvement in system miniaturization and Local Area

Networking (LAN).Technology to distribute the processing across multiple

systems

LANs are share the information with each other in real time

This Primarily communicating with field dives such as RTU HMI

This distributed scada system improve the redundancy and reliability

All the stations are online state al the time

The WAN used to communicate with devices in the field were largely

unchanged by the development of LAN connectivity between local

stations at the SCADA master.

DISTRIBUTED SCADA SYSTEMS:

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The second generation of SCADA systems was also limited to hardware,

software, and peripheral devices that were provided or at least selected by the

vendor.

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. The major improvement in the third generation is system architecture, utilizing

open standards and protocols and making it possible to distribute SCADA

functionality across a WAN and not just a LAN.

NETWORKED SCADA SYSTEMS:

These vendors have looked to system vendors such as Compaq, Hewlett-

Packard, and Sun Microsystems for their expertise in developing the basic computer

platforms and operating system software

The major improved in third generation SCADA systems comes from the use ofWAN protocols such as the Internet Protocol (IP) for communication between the

master station and communications equipment (RTU)

RTUs communicate with the master station using an Ethernet connection

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Hardware Arch itectureSCADA products -CERN in view of their possible application to the control systems

of the LHC detectors

One distinguishes two basic layers in a SCADA system:

"client layer" - caters for the human machine interaction and the

"data server layer" handles the data control activities called controllers(PLCs)

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SOFTWARE ARCHITECTURE

The products are multi-tasking and are based upon a real-time database (RTDB)

located in one or more servers.

Servers are responsible for data acquisition and handling

INTERFACINGSCADA to access devices in an open and standard manner is developing.

An Open Data Base Connectivity (ODBC) interface to the data in thearchive/logs,

but not to the configuration database,

An application interfaces supporting C,C++ etc.,

Database

Data are stored in a database that is logically centralized but physically distributed

Most of the SCADA products were decompose the process in "atomic" parameters

to which a Tag-name is associated.

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SCALABILITY

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

The products achieve scalability by having multiple data servers connected to multiplecontrollers

Each data server has it own RTDB configuration.

REDUNDANCY

The products often have built in software redundancy at a server level.

FUNCTIONALITY

ACCESS CONTROLwhich allocates the groups to read/write privileges

MMI: products supports multiple screens

Most of the SCADA products that were evaluated decompose the process in

"atomic" parameters

Standard windows editing facilities are provided: zooming, re-sizing, scrolling

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TRENDINGThe products all provide trending facilities and one can summaries the common

capabilities

zooming and scrolling functions are provided

historical trending is possible for any archived parameter

real-time and historical trending are possible

ALARM HANDLINGAlarm handling is based on limit and status checking and performed in the data

servers

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

users see the same status

LOGGING/ARCHIVING Logging can be thought of as medium-term storage of data on disk,

Archiving is long-term storage of data either on disk or on another permanent

storage medium

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REPORT GENERATION :reports using SQL type queries to the archive

APPLICATION DEVELOPMENT

PC tools now have a Windows Explorer

An Application Program Interface (API) supporting C, C++, VB

OBJECT HANDLING

In general the products do not handle objects, but rather handle individual

parameters,

e.g., alarms are defined for parameters, logging is performed on parameters and

control actions are performed on parameters

EVOLUTION:as new technologies are concerned, the SCADA products are

now adopting

Web technology, ActiveX, Java, etc.OPC as a means for communicating internally between the client and server

modules

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Engineering

engineering activities specific to the use of a SCADA system are the definition of:

a mechanism to prevent conflicting controls

instructions on how to control e.g. a device

templates for different types of "panels", e.g. alarms

POTENTIAL BENEFITS OF SCADA

Reliability and robustness

Technical support and maintenance by the vendor

A rich functionality and extensive development facilities

FUTURE SCOPE:SCADA systems, (supervisory, control and data acquisition), play a vital role

in the operation of electricity utilities.

SCADA systems are used to monitor and control their equipment, which is

usually spread over a large geographical area.

installation in harsh electrical and physical environments

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CONCLUSION

It is realized that SCADA systems play a vital role in power system operations

viz load dispatch centre, substation automation and distribution automation.

APCPDCL stands as one of the best state electricity distribution organizations in

the country

the exact status of breakers and helped a lot in reducing interruptions

occurrence of sudden disturbances

Distribution automation through SCADA also reduces human influence and

errors.

It offers complete power system controls and data acquisitions

Mainly it provides the quality of power supply

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BIBLIOGRAPHY

[1] A.Daneels, W.Salter, "Technology Survey Summary of Study Report", IT-

CO/98-08-09, CERN, Geneva 26th Aug 1998.

[2] A.Daneels, W.Salter, "Selection and Evaluation of Commercial SCADA

Systems for the Controls of the CERN LHC Experiments", Proceedings of the

1999 International Conference on Accelerator and Large Experimental

Physics Control Systems, Trieste, 1999, p.353.

[3] G.Baribaud et al., "Recommendations for the Use of Field buses at CERN

in the LHC Era", Proceedings of the 1997 International Conference on

Accelerator and Large Experimental Physics Control Systems, Beijing, 1997,

p.285.

[4] R.Barillere et al., "Results of the OPC Evaluation done within the JCOP for

the Control of the LHC Experiments", Proceedings of the 1999 International

Conference on Accelerator and Large Experimental Physics Control Systems,

Trieste, 1999, p.511.

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