SCADA

SCADA
Eyes and Ears for the operator

What is SCADA?
• SCADA abbreviates for Supervisory Control And
Data Acquisition system
• Definition – It is a system operating with coded
signals over communication channels so as to
provide control of remote equipment.
Source: www.engineersgarage.com

Elements of SCADA system
• SCADA Master Station Computer System
• Human Machine Interface
• Remote Terminal Units
• Programmable Logic Controllers
• SCADA communications

SCADA Master Station Computer
System
• It is the repository of the real-time or near real-time
reported data collected from the remote terminal
units connected to it.
• It is generally standard computer hardware
equipment.
• The back end SCADA software must be able to
repeatedly poll the RTUs for data values, should have
software for their retrieval, storage and processing.

Human-Machine Interface
• This is the eye candy part on the host station
• The values that have been stored in the host
computers are presented to the human operator in an
understandable and comprehensible form using
HMIs
• These may provide trending, diagnostic or
management information and detailed schematics
and animations representing the current states of the
machines under its control

Remote Terminal Units
• An RTU is a normally a transducer or a sensor which
allows the electrical circuitry to interface with the process
instrumentation and control equipment.
• A single RTU may measure many different types of
parameters
• The Input/Output circuitry of a RTU can be analog or
digital
• RTUs are microprocessor based devices and these
conversions are primarily internal to them.

Programmable Logic Controllers
• PLCs have been built around the philosophy of
automation
• Re-programmability being the biggest asset
• PLC based RTUs can be fixed on the field itself along
with adding new features like support for multiple polling,
exception reporting, time tagging etc.
• This also enables them to execute simple logical processes
without involving the master station

SCADA Communication
• The conveying of data from an RTU to the master
station and commands from the host to the RTU need to be
done over a communication system
• SCADA system might not be localized to just a single plant
• The vastness of the network also has to be catered to along
with speed, accuracy, security and performance being among
other important issues
• Before the computer networking communication were voice
communication based
• It has now embraced LANs and WANs for seamless integration
with everyday office computer networks

Generation of SCADA systems
• 1st gen – Monolithic SCADA Systems
• 2nd gen – Distributed SCADA Systems
• 3rd gen – Networked SCADA Systems
• 4th gen – Internet of Things Systems

Monolithic SCADA Systems
• Owing to their origins in times when computing revolved
around standalone ‘Mainframe computers’ with networks being
virtually non-existent
• The communication between RTU and the central computer
was a dedicated line solely for that purpose
• Redundancy was provided by connecting a similar mainframe at
the bus level which continuously monitored and took over the
main computer in case of failure

Distributed SCADA Systems
• It uses the LAN networks to its advantage, the computing load
was distributed across multiple systems
• Each system being given a specific function like communication
processor, calculation processor, database server etc. and
sharing information in real time
• This had a limitation of geographical extent and could not be
used for widely distributed systems
Note: The use of WAN to provide communication between the
RTUs and the main distributed system remained unchanged.

Networked SCADA Systems
• Based on the second generation, it follows open system
architecture
• Using Open standards mitigates many limitations allowing cross
vendor compatibility and the use of any off-the-shelf standard
product
• The use of WAN networks like Internet Protocol for
communication has separated the Main master station from the
network by the use if an intervening communications server,
thus adding another layer of security to the data and improved
disaster survivability

Internet of Things
• With the commercial availability of cloud computing,
it has adopted Internet of Things technology to
reduce infrastructure costs and increase ease of
maintenance and integration
• Can implement more complex control algorithms
than are practically feasible to implement on
traditional programmable logic controllers
Source: en.wikipedia.org

Where is SCADA used ???
• SCADA is used to manage any kind of gear.
• Typically SCADA systems are used to automate complex
processes where human control is impractical.
• Systems where there are more control factors, than
human beings can comfortably manage.
Source: www.dpstele.com

Continued…
1) Electric power Generation, Transmission &
Distribution – Utilities use SCADA system to direct
current, flow and line voltage, to monitor the
operation.
2) Water & Sewage
3) Manufacturing
4) Buildings, Facilities &
Environment
5) Mass Transit
6) Traffic signals

Benefits of SCADA
• Reliability & Robustness-These systems are used for mission
critical industrial processes where reliability and performance are
paramount.
• Maximize productivity- Maximizes productivity and ensures
continuous production.
• Improve product quality- Analyzes and controls the quality of
manufactured products using standard SCADA functionality.
• Reduce your operating and maintenance costs- Fewer
personnel are required to monitor & less maintenance trips are
required.
• Integrate with your business systems- A SCADA system can be
easily integrated with your existing business systems, leading to
increased production and profitability.

Use of SCADA – Process control

SCADA

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