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Supervisory control and data acquisition

What is SCADA?

SCADA ( Supervisory Control and Data Acquisition ) : SCADA is a aggregation of equipment that provides monitoring and control of procedure and parametric quantities of a cardinal site. As a effect of immense industries and workss an operator has to supervise and command 1000s of detectors. As the definition itself says this system supervises and controls existent clip informations gathered distant site. SCADA system is used to supervise and command a works or equipment in industries. Supervisory control and informations acquisition ( SCADA ) engineering collects real-time informations from virtually any environment where there is a demand to supervise machinery or procedures. As such, it is strictly package bundle that is positioned on top of hardware to which it is interfaced, in general via Programmable Logic Controllers ( PLC ‘S ) , or other commercial hardware faculties. SCADA system can be built by different sorts of engineerings and protocols.

Why SCADA is used?

If a mistake occurs in a immense web operator has to happen the mistake and he has to hotfoot to the mistake location without hold to avoid break of work. By utilizing a SCADA system an operator can supervise and command the whole procedure from his place by giving proper instructions.SCADA systems are used where human control is impractical. And they can rectified or controlled faster than a human being. This systems are used in the immense webs with multiple control factors, and the control factors vary in fraction of seconds where an operator control is non possible, than human existences can comfortably pull off. Real clip monitoring and control of a system optimizes efficiency and profitableness. Automation eliminates human mistakes accomplishing better productiveness, dependability and optimisation with lesser use of resources and clip. By utilizing this sort of mechanization the system can be monitored uninteruptly without breaks.. The full system can be monitored over a web, from a cardinal location through the Internet or a dial-up line or telephone line.Cables and wired communicating was used in older yearss but this is limited to little area.In power workss to supervise transmittal SCADA is used in this scenario utilizing overseas telegrams LAN for communicating is non possible so wireless communicating is used.

Where is SCADA used?

Areas of SCADA systems control:

  • Power Systems: SCADA is used in Electric power coevals, transmittal and distribution to analyse burden flow analysis, to foretell the control operation within the statutory bounds as prescribed.
  • Water and sewerage: SCADA is used to supervise and modulate H2O flow, Water Leak sensing and location, Treatment workss incorporate local / remote control, Pumping station automatic direction

Functionality – dismay detection and event monitoring, informations acquisition, web operator interface, non existent clip control, Data bases and informations logging, usage of MMI, logging/archiving, study coevals, mechanization.

There are three chief categorization in SCADA system:

  • RTU ‘s ( Remote Telemetry Units ) ,
  • Communicationss
  • HMI ( Human Machine Interface ) .

These operations are performed by Master station, MMI/HMI and RTU or PLCs, Communication web.

  • RTUs or PLCs: Thesiss are Data interface devices which interface to field feeling devices. These are little computerized units will be located at distant countries where data/control should be taken these devices are interfaced to detectors and switches and gathers studies from them and delivers informations. Remote telemetry unit converts electric signals at distant site to digital signals as the detectors and control relays are simple electric devices they ca n’t pass on with protocols on their ain.Remote telemetry unit ( RTU ) acts as an interface between the detectors and the SCADA web. Most of the commanding in SCADA system is done by RTU ‘s and PLC ‘s.
  • Communication Network: A communicating web used to reassign monitored or controlled informations between monitoring devices, commanding units and waiters or cardinal computing machines in the SCADA or maestro station. The media for Communication system may be wireless, telephone lines, overseas telegram, orbiter, etc combination of any of these.
  • Maestro Station: A cardinal host computing machine waiter or waiters ( sometimes called a SCADA Center, maestro station, or Master Terminal Unit ( MTU ) . It is the chief organic structure of the Master station serves as the cardinal processing unit for the SCADA system. Master station consists of assorted faculties like Historical Management System, Trend Management System, Log Management System, Alarm Management System etc. MTU predicts human interface to the system and automates ordinance of the managed system in response to sensor inputs.
  • HMI/MMI: It is an interface where information is processed and presented to the operator to supervise and command. This acts as an interface between SCADA system and operator so it is called Human Machine Interface or Man Machine Interface. A Human-Machine Interface is the system which ensures procedure informations from maestro system to a web operator, and by which the operator controls the procedure.

How SCADA Systems Work

SCADA system functionality is divided into four maps:

  1. Data acquisition
  2. Data Communication
  3. Data presentation
  4. Control

Data Acquisition: Data acquisition is aggregation of existent clip data.With the inauspicious impact of immense equipments and workss SCADA system has to supervise 100s of sensors.The full system can be monitored with informations acquisition. Data acquisition is the information engineering It is designed to aggregation of informations, entering the collected informations, hive awaying and analysing the informations gathered from electronic devices such as detectors or gages. Data acquisition is meant for digitising of electric signals and processing of multiple detector or signal inputs. Supervisory and informations acquisition is an application that collects informations from distant site for treating from a centralized computing machine. common end of geting, analysing, and showing information. Data Acquisition systems can besides organize portion of a procedure control system by usage of appropriatesoftware provides direct digital control of assorted procedure. Data acquisition systems integrated signals, detectors, actuators, signal conditioning, informations acquisition devices, and application package.

Data acquisition package variedly used from simple data-collection to high degree plans for mensurating and commanding procedure. DAQ package gaining control device informations from graduated tables, gages and barcode-scanners in existent clip. Data acquisition package reads device informations from TCP/IP protocol. This package is used to command procedures such as get downing or halting a counter, directing control bid to an analog-to-digital convertor, garnering informations points at regular intervals from a detector or a switch. Some of the complex informations acquisition package is used for showing the information gathered in the signifier of assorted representations, likely graphical and pictural pictural representations such as graphs or 3-dimensional graphics.Data monitored is saved in the database. The HMI of a SCADA system is where processed information is presented to be monitored by a human operator.

Data Communication: In existent universe, for supervising multiple systems from a cardinal location, we need a communications web to reassign all the informations collected from distant country to cardinal station and processed informations from cardinal station to HMI/MMI Vice-Versa. Earlier SCADA webs are communicated over wireless telephone lines, modem or dedicated consecutive lines. Now we are utilizing Ethernet, IP and in immense workss wireless communicating is used.To transportation informations gathered firmly this is SCADA information is encoded and transferred over the secure protocols. These are designed to be really compact.. RTU converts the electrical signals from the equipments like detectors and relays to digital values.RTU accent like a interface between the detectors in the distant location and the SCADA system. Distant telemetry unit RTU are used to convey informations from distant country to cardinal station and the RTU receives command bids in protocol format from the cardinal and converts electrical signals and transportations to the appropriate control relays.

Data Presentation: The informations received from RTU ‘s or PLC ‘s will be displayed to the web operator over computing machine system in cardinal station, human machine interface ( HMI ) .Central station proctors the whole system like detectors. It predicts the operator the operation of the system as graphical representation or pictural representation. It alerts the operator when there is a malfunctioning in the system with dismaies.

Control: The informations gathered from distant site is controlled automatically largely by Remote Terminal Units ( “ RTUs ” ) or by Programmable Logic Controllers ( “ PLCs ” ) with predefined set of values. An operator with Human Machine Interface ( HMI ) monitors the state of affairs and he will go through the several control commands. SCADA system may let operators to alter the predefined parametric quantities values for the flow, circuit ledgeman operation, get downing and halting of a counter, and enable dismay conditions, high temperature, to be displayed and recorded. The whole control can be achieved from a cardinal location without any hazard. The public presentation of the system after go throughing the control commands is monitored.


By utilizing SCADA system, big web holding several bring forthing Stationss and substations and big burden centres is controlled from centralized burden despatch. Scada system accent on electricity public-service corporation remotely-monitor coordinate, control transmittal and distribution constituents and devices in existent clip from a distant country with acquisition of informations for analysis and planning from one control country. Most SCADA systems run either on a UNIX discrepancy or on VMS.


In this system the existent clip informations from the power system is gathered from transducers which converts the a.c. signals from the Current transducers and Power transducers to the dc signal proportional to the measured value for the several parametric quantities is converted to the digital signals. These transducers are interfaced with RTU ( Remote Terminal Unit ) , which is located at the bring forthing Stationss or substations the information is transmitted to the burden control centre through power line bearer system ( PLCC ) , fiber optics communicating and microwave channels. Thus the information acquisition is done. The information, which is processed by the computing machine systems using energy direction package, provides automatic and distant control of the web at the burden control Centre. Then the instructions from the burden control country are transmitted to the control suites of the substation and bring forthing station for put to deathing appropriate action.

Digital computing machines and microprocessor installed in the control suites of big substation bring forthing station and burden control country are used for informations aggregation, informations monitoring and a automatic control.

Therefore, by using SCADA system to power distribution web provides incorporate attack to the power system protection, operation control and monitoring automatically with least intercession of control room operator.


  • Data acquisition: Provides measurings and position to operators.
  • Representing secret plans and measurings on selected clip intervals.
  • Supervisory control: Enables operators remotely control devices circuit surfs and relays.

SCADA employs web operators to command circuit surfs disconnect switches change transformer lights-outs and stage shifter place remotely. It enables operators to supervise the coevals and high electromotive force transmittal system to foretell over tonss or out of bound electromotive forces. It

Proctors all switch gear place, substation tonss and electromotive forces, capacitance Bankss, tie line flows and interchange agendas. It detects through telemetry the failures and mistakes in bilateral communicating links between computing machine and distant equipment. These maps are scanned every fraction of 2nd exactly.

SCADA provides position and measurings for distribution feeders at substation. It renders client metre, implement clip of twenty-four hours pricing and exchange client equipment to pull off burden and improves functionality of distribution control Centre.

SCADA is extensively used for digest of extended informations and direction of distribution systems. Stumbling due to human mistakes can be avoided eminently.

By utilizing SCADA system manual mistakes and inadvertences are made about negligible, the system provides periodic studies that aid in analysis of public presentation of power system. Distribution web supervising maps with geographical function, mistake location. At coevals ‘distributed control ‘ has reduced the cabling cost within the works and has potency of replacing control suites with distributed CRT/keyboard Stationss. Data Acquisition collects informations from peculiar points in the power system converts these into technology units. All these inputs are brought through overseas telegrams to terminuss. This information is supplied to execute following maps.

  1. a ) Analogue: Continuous Electrical Signals Ex. Active Power ( MW ) , Reactive Power ( MVAR ) , Voltage ( KV ) , Frequency ( Hz ) .etc. B ) DIGITAL: Switch Signals High ( 1 ) or Low ( 0 ) Signal Ex. Breaker Close ( high ) or Open ( low ) , Isolator Closed ( high ) or Open ( low ) .
  2. Process- a ) The signals are converted into digital format. B ) Implement protocol between Master and Slave. degree Celsius ) It operates with Real Time Operating System ( RTO ) .
  3. Output- a ) The consequences are exposed with user friendly environment. B ) Through shows can be possible to command the substation and bring forthing station.
  • Display on CRT screen
  • Graphic show of works sub-systems
  • Datas logging
  • Alarm coevals
  • Event logging
  • Trending of parallel variables
  • Performance computation
  • Generating control signals.

The CRT ‘s in control room enables operator to expose of dismaies, works variables. To see the information of works along with existent clip variables and position information. The bounds of all variables are checked if any variable is out of scope an dismay is raised. The position alterations and clip of happenings are maintained accurately in order to keep quality analysis expeditiously all the equipments are sporadically calculated.


The electrical energy is transferred from big bring forthing Stationss to distant burden centres via assorted sub-stations. In every sub-station certain supervising, control and protection maps are necessary. Every substation has a control room. The relay and protection panels and control panels are installed in the control room. The assorted circuit surfs, pat modifiers and other devices are controlled by matching control-relay panels. In a little independent sub-station, the supervising and operation for normal service can be carried out by the operator with the assistance of parallel and digital control systems in the works. The surfs can be operated by distant control from the control room. During mistakes and unnatural conditions, the surfs are operated by protective relays automatically. Therefore, the primary control in sub-station is of two classs.

  1. Normal everyday operation by operators command.
  2. Automatic operation by action of protective relays and control systems.


1. Alarm Functions

  • To sound alarm/annunciation sing unsafe, uncommon events such as unnatural values of procedure parametric quantities, fire, illegal entry in premises, over temperatures, low electromotive force of subsidiary supply, unusual go oning etc. Alarms are obtained from informations lumberman and are for alarming this operator in the control room.

2. Control and Indication

  • Control of two place devices such as circuit-breakers, isolators, earthing-switches, starting motors. Indication of ON/OFF province of the devices on control board/mimic diagrams.
  • Control of place of devices holding places ( closed, in-between unfastened ) e.g. values, input scenes, indicant of place on control panels.
  • Control places of multi-position device e.g. pat modifier, indicant of place on control panels.
  • Indication without control.
  • Control without indicant: e.g. rise or lower control of generator burden by automatic burden frequence control.
  • Set-point control to supply put point to a accountant located at distant sub-station.

3. Data aggregation, entering, show.

4. Consecutive operation of devices with preset clip and conditions for operation of assorted devices


  • Auto-reclosing of circuit-breakers operation O-CO-Time-CO
  • Operation of circuit-breaker, isolator and earthing switch in a peculiar sequence during gap of circuit and another sequence during shutting of circuit.

5. By agencies of SCADA system, the operator in control Centre can do operations in a distant sub-station. The possible distant operations include:

  • Opening and shutting of exchanging devices I
  • Tap-changing of transformers ( voltage control )
  • Switch overing of capacitance Bankss ( voltage control )
  • Load casting ( load frequence control )

6. Some of the distant operations are made automatic by one-line computing machine based system without human intercession e.g. Net work islanding, Backup protection. The automatic control map are segregated into:

  • Interconnection maps
  • Transmission line automatic map
  • Distribution system automatic maps

Therefore by utilizing SCADA system addition in capacity use in coevals. ii.Saving energy and natural stuffs due to increased operational efficiency.SCADA system proctors and controls the grid and improves effeciancies and dramas cardinal function in keeping the power system security.By utilizing SCADA system monitoring and controlling can be done from anyplace in universe by utilizing wireless webs.


  • Sing and monitoring of existent clip informations.
  • Time synchronism with GPS
  • Supervisory Control
  • Powersystem co-ordination and Control through communicating.
  • Alarms for any unnatural status in the system.
  • Surveies can be done.
  • Optimum Power Utilization through computing machines.
  • Planning of electrical power place in the province.
  • Minimization of Man Power.
  • Monitoring the larceny of power in any place of transmittal.
  • Cost of Salvaging Revenues.
  • Faster Restoration of normal gross.
  • Minimizing outages of equipment.
  • User friendly study coevals.
  • Web integrating.
  • Energy Management


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