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Abstract-- SCADA is a type of Industrial control system.

In reality, the primary purpose of SCADA is to monitor,

control and alarm plant or regional operating systems from a

central location. SCADA system consists with these following

elements, HMI (human–machine interface), a supervisory

system, remote terminal units, PLC, Communication

infrastructure and methods.

Index Terms— 1. Definition

2. Main Functions of SCADA

3. Controlling Process

4. Components of SCADA

5. Systems concepts

6. SCADA architectures

7. Security issues

8. Advantages of SCADA system

9. Future of SCADA system

I. INTRODUCTION

SCADA stands Supervisory Control and Data Acquisition.

As the name indicates, it is not a full control system, but

rather focuses on the supervisory level. It is a computer

system for gathering and analyzing real time data.

SCADA systems are used to monitor and control a plant or

equipment in industries such as telecommunications,

water and waste control, energy, oil and gas refining and

transportation. A SCADA system gathers information,

such as where a leak on a pipeline has occurred, transfers

the information back to a central site, alerting the home

station that the leak has occurred, carrying out necessary

analysis and control, such as determining if the leak is

critical, and displaying the information in a logical and

organized fashion. SCADA systems can be relatively

simple, such as one that monitors environmental

conditions of a small office building, or incredibly

complex, such as a system that monitors all the activity in

a nuclear power plant or the activity of a municipal water

system.

II. MAIN FUNCTIONS OF SCADA

Data acquisition,

Alarms and event monitoring,

Database and data logging,

Operator interface,

Non real time control,

Logging,

MMI (men- machine interface) use,

Automation, and

Report generation

III. CONTROLLING PROCESSES

Processes done by SCADA can be classified by the

following points;

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, wind farms 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

IV. COMMON COMPONENTS OF SCADA

1. HMI (Human Machine Interface): It is an

apparatus that is operated by human to monitor

and control various processes.

2. PLC (Programmable Logic Controller): This

controller is used because they are very flexible,

and economical than Remote Terminal Units

3. Supervisory System: It collects process data and

sends control commands to the process.

4. RTU (Remote Terminal Units): This process is

connected with sensors to convert sensor signals

into digital and sends digital data to Supervisory

System

5. Communication Infrastructure: It is connecting

Supervisory System to RLU’s.

V. SYSTEMS CONCEPTS

The term SCADA usually refers to centralized systems

which monitor and control entire sites, or complexes of

systems spread out over large areas (anything from an

industrial plant to a nation). Most control actions are

performed automatically by RTUs or by 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

Supervisory Control and Data Acquisition

(SCADA)

Towfiqur Rahman (ET091010)

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SCADA system monitors the overall performance of the

loop.

Fig. 1. Basic SCADA Structure

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. Data may

also be fed to an Historian, often built on a commodity

Database Management System, to allow trending and

other analytical auditing.

SCADA systems are significantly important systems used

in national infrastructures such as electric grids, water

Supplies and pipelines. However, SCADA systems have

many security vulnerabilities.

VI. SCADA ARCHITECTURES

SCADA systems have evolved in parallel with the growth

and sophistication of modern computing technology. The

following sections will provide a description of the

following three generations of SCADA systems:

I. First generation: Monolithic; when SCADA systems

were first developed, the concept of computing in

general centered on “mainframe” systems.

Networks were generally non-existent, and each

centralized system stood alone. As a result,

SCADA systems were standalone systems with

virtually no connectivity to other systems. Wide

Area Networks were later designed by RTU

vendors to communicate with the RTU. The

communication protocols used were often

proprietary at that time. The first-generation

SCADA system was redundant since a back-up

mainframe system was connected at the bus level

and was used in the event of failure of the

primary mainframe.

Fig. 2. First Generation of SCADA system

II. Second generation: Distributed; 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. Multiple stations, each

with a specific function, were connected to a LAN

and shared information with each other in real-

time. These stations were typically of the mini-

computer class, smaller and less expensive than

their first generation processors.

Fig. 3. Second Generation of SCADA system

III. Third generation: Networked; The current generation

of SCADA master station architecture is closely

related to that of the second generation, with the

primary difference being that of an open system

architecture rather than a vendor controlled,

proprietary environment. There are still multiple

networked systems, sharing master station

functions. There are still RTUs utilizing protocols

that are vendor-proprietary. The major

improvement in the third generation is that of

opening the system architecture, utilizing open

standards and protocols and making it possible to

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distribute SCADA functionality across a WAN

and not just a LAN.

Fig. 4. Third Generation of SCADA system

VII. SECURITY ISSUES

Supervisory control and data acquisition (SCADA)

networks contain computers and applications that perform

key functions in providing essential services and

commodities (e.g., electricity, natural gas, gasoline, water,

waste treatment, transportation). As such, they are part of

the nation’s critical infrastructure and require protection

from a variety of threats that exist in cyber space today.

Against a backdrop of newly emerging threats, security

managers at organizations that use SCADA are beginning

to address the challenges involved in securing these

systems. Much of what needs to be done is simply

implementing sound information-security practices.

The following are TSI’s (The Security Institute, a United

Kingdom based professional body for security

professionals) recommendations to address some lingering

security issues:

Security of network communications:

Implementation of strong encryption over the

SCADA network communications, to ensure that

both monitored data and control commands are

encrypted.

Turning on security: Implementation of security

features with devices on the network, especially

authentication. Using secure protocols whenever

possible.

Knowing your SCADA network: Identifying all

connections to external networks including wire-

less networks, corporate LANs and WANs, and

the Internet. Also, securing the network by

eliminating all unnecessary connections to

external networks.

Hardening of the SCADA environment: Removing

all unnecessary services from the hosts on the

network. Also, just as in the corporate network

environment, ensuring that all systems are

patched and up to date.

Conducting regular security audits: Ensuring that

security practices and procedures, such as

incident response, are defined and implemented.

Penetration testing of the network environment

should also be prudently conducted with

inspection for potential back doors into the

SCADA network.

Implementing real-time threat protection: With the

increasing number and complexity of attacks, it's

insufficient to simply patch the systems or

maintain access/service control. One alternative

is to implement real-time threat protection in the

form of network intrusion-prevention systems.

Unlike standard packet-filter firewalls, these

systems perform application-layer inspection to

identify attacks that are carried in the payload

and block the offending traffic in real time.

VIII. ADVANTAGES OF SCADA SYSTEM

A SCADA system when applied properly can help

industries to save time and money. One reason is that with

SCADA, it can eliminate the need for site visits by

personnel for inspection, adjustments and data collection.

SCADA software enables to monitor the operations in real

time. It can also make modifications to the system, auto-

generate reports and trouble-shoot.

Thus once the system is installed, it reduces operational

costs and improves the efficiency of the set-up. SCADA

systems are equipped to make immediate corrections in the

operational system, so they can increase the life-period of

your equipment and save on the need for costly repairs. It

also translates into man-hours saved and personnel

enabled to focus on tasks that require human involvement.

Further, the auto-generated reporting system ensures

compliance with regulatory principles.

IX. The Future of SCADA system

The large territories and huge volumes of data SCADA

can handle form a formidable combination. Today’s

SCADA systems can manage anything from a few

thousands to one million of input/output channels.

The technology is still evolving in terms of sophistication

as well. SCADA systems as they are now can perform a

large variety of tasks and some systems have artificial

intelligence built into them. They are also more network-

enabled, thus paving the way for voice-data-control data

convergence. With proper planning and a custom-made

installation, a SCADA system becomes a valuable asset.

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X. ACKNOWLEDGMENT

We gratefully acknowledge the contributions of Md.

Amin for his class lecture on this topic.

XI. REFERENCES

Technical Reports: 1. wikipedia.org

2. power systems loss: SCADA ARCHITECTURES

http://www.powersystemsloss.com/2012/01/scada-architectures-

monolithic-system.html

3. SCADA | Supervisory Control and Data Acquisition | Security for

SCADA

http://www.tsips.com/SCADA.htm

4. Latest Advancements in Distribution SCADA - Electric Light &

Power

http://www.elp.com/articles/powergrid_international/print/volum

e-17/issue-9/feaures/latest-advancements-in-distribution-

scada.html

5. Why SCADA?

http://www.roseindia.net/technology/scada/why-SCADA.shtml

6. Class Lecture

Standards: Preparation of a Formatted Technical Work for the IEEE Power & Energy

Society

XII. BIOGRAPHIES

Towfiqur Rahman was born in 1989 at

Chittagong. He completed his HSC from Govt.

City College at 2007. He is now studying at

International Islamic University Chittagong in

Electrical and Electronics Engineering, final year.