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SCADA

SCADA (supervisory control and data acquisition) generally refers to industrial control systems:computer systems that monitor and control industrial, infrastructure, or facility-based processes, asdescribed below:

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 anddistribution, 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.

SCADA architecture

First generation: "Monolithic"

In the first generation, computing was done by mainframe computers. Networks did not existat the time SCADA was developed. Thus SCADA systems were independent systems with noconnectivity to other systems. Wide Area Networks were later designed by RTU vendors tocommunicate 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 wasconnected at the bus level and was used in the event of failure of the primary mainframe system.

Second generation: "Distributed"

The processing was distributed across multiple stations which were connected through a LANand they shared information in real time. Each station was responsible for a particular task thusmaking the size and cost of each station less than the one used in First Generation. The networkprotocols used were still mostly proprietary, which led to significant security problems for any SCADAsystem that received attention from a hacker. Since the protocols were proprietary, very few people

beyond the developers and hackers knew enough to determine how secure a SCADA installationwas. Since both parties had vested interests in keeping security issues quiet, the security of aSCADA installation was often badly overestimated, if it was considered at all.

Third generation: "Networked"

These are the current generation SCADA systems which use open system architecture rather than a vendor-controlled proprietary environment. The SCADA system utilizes open standards andprotocols, thus distributing functionality across a WAN rather than a LAN. It is easier to connect thirdparty peripheral devices like printers, disk drives, and tape drives due to the use of open architecture.WAN protocols such as Internet Protocol (IP) are used for communication between the master stationand communications equipment. Due to the usage of standard protocols and the fact that manynetworked SCADA systems are accessible from the internet; the systems are potentially vulnerable toremote cyber-attacks. On the other hand, the usage of standard protocols and security techniques

means that standard security improvements are applicable to the SCADA systems, assuming theyreceive timely maintenance and updates.

MMI (Man- Machine Interface)

It stands for "Man-Machine Interface" and, as you may gather from the name, is the hardwareand/or software which allows the operator, engineer, etc. to control and monitor the machine function, asopposed to the hardware and/or software that contains the logic by which machine operation iscontrolled. MMI means "Man-Machine Interface." MMI's are used to provide control and status for 

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automated systems. For example, this could be the screen that a machine operator uses to start amachine cycle, or set the number of cycles the system needs to run, or see the reason why the systemstopped, and so on. These used to be boards made up of pilot lights, pushbuttons, and selector switches,and you still see these on many older systems. However, the cost of all those individual pilot lights,pushbuttons, & the cost to wire them back to a controller is usually more expensive than most solid-statetype MMI's today. Plus, the MMI screens take up less space and can be changed relatively easilycompared to push button stations, especially when adding more lights & buttons to a system. By the way,each pilot light & push button needs to be wired up to it's own I/O point (and sometimes to more than oneI/O point) on a controller, which usually increases the amount of controller I/O modules required for your system, which increases the system cost.

DIRECT DIGITAL CONTROL

Direct digital control (DDC) is the automated control of a condition or process by a digital device(computer).

A very early example of a DDC system meeting the above requirements was completed by theAustralian business Midac in 1981-1982 using R-Tec Australian designed hardware. The system installedat theUniversity of Melbourne used a serial communications network, connecting campus buildings backto a control room "front end" system in the basement of the Old Geology building. Each remote or Satellite Intelligence Unit (SIU) ran 2 Z80 microprocessors whilst the front end ran 11 in a Parallel Processing configuration with paged common memory. The z80 microprocessors shared the load bypassing tasks to each other via the common memory and the communications network. This was possiblythe first successful implementation of a distributed processing direct digital control system.

SAFETY INSTRUMENTED SYSTEM

A Safety Instrumented System (SIS) is a form of process control usually implemented inindustrial processes, such as those of a factory or an oil refinery. The SIS performs specified functions toachieve or maintain a safe state of the process when unacceptable or dangerous process conditions aredetected. Safety instrumented systems are separate and independent from regular control systems butare composed of similar elements, including sensors, logic solvers, actuators and support systems.

The specified functions, or safety instrumented functions (SIF) are implemented as part of anoverall risk reduction strategy which is intended to reduce the likelihood of identified hazardous eventsinvolving a catastrophic release. The safe state is a state of the process operation where the hazardousevent cannot occur. The safe state should be achieved within one-half of the process safety time. MostSIF are focused on preventing catastrophic incidents.

The correct operation of an SIS requires a series of equipment to function properly. It must havesensors capable of detecting abnormal operating conditions, such as high flow, low level, or incorrectvalve positioning. A logic solver is required to receive the sensor input signal(s), make appropriatedecisions based on the nature of the signal(s), and change its outputs according to user-defined logic.The logic solver may use electrical, electronic or programmable electronic equipment, such as relays, trip amplifiers, or programmable logic controllers. Next, the change of the logic solver output(s) results in thefinal element(s) taking action on the process (e.g. closing a valve) to bring it to a safe state. Support

systems, such as power, instrument air, and communications, are generally required for SIS operation.The support systems should be designed to provide the required integrity and reliability.

International standard IEC 61511 was published in 2003 to provide guidance to end-users on theapplication of Safety Instrumented Systems in the process industries. This standard is based on IEC 61508, a generic standard for design, construction, and operation of electrical/electronic/programmableelectronic systems. Other industry sectors may also have standards that are based on IEC 61508, suchas IEC 62061(machinery systems), IEC 62425 (for railway signaling systems), IEC 61513 (for nuclear systems), and ISO 26262 (for road vehicles, currently a draft international standard).

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DISTRIBUTED CONTROL SYSTEM

A distributed control system (DCS) refers to a control system usually of a manufacturing system, process or any kind of dynamic system, in which the controller elements are not central inlocation (like the brain) but are distributed throughout the system with each component sub-system

controlled by one or more controllers. The entire system of controllers is connected by networks for communication and monitoring.

DCS is a very broad term used in a variety of industries, to monitor and control distributed equipment.

Electrical power grids and electrical generation plants

Environmental control systems

Traffic signals

radio signals

Water management systems

Oil refining plants

Metallurgical  Process Plants

Chemical plants

Pharmaceutical  manufacturing

Sensor networks

Dry cargo and bulk oil carrier  ships

Applications

Distributed Control Systems (DCSs) are dedicated systems used to control manufacturingprocesses that are continuous or batch-oriented, such as oil refining, petrochemicals, central stationpower generation, fertilizers, pharmaceuticals, food & beverage manufacturing, cement production,steelmaking, and papermaking. DCSs are connected to sensors and actuators and use setpoint control tocontrol the flow of material through the plant. The most common example is a setpoint control 

loop consisting of a pressure sensor, controller, and control valve. Pressure or flow measurements aretransmitted to the controller, usually through the aid of a signal conditioning Input/Output (I/O) device.When the measured variable reaches a certain point, the controller instructs a valve or actuation device toopen or close until the fluidic flow process reaches the desired setpoint. Large oil refineries have manythousands of I/O points and employ very large DCSs. Processes are not limited to fluidic flow throughpipes, however, and can also include things like paper machines and their associated quality controls(see Quality Control System QCS), variable speed drives and motor control centers, cement kilns, miningoperations, ore processing facilities, and many others. A typical DCS consists of functionally and/or geographically distributed digital controllers capable of executing from 1 to 256 or more regulatory controlloops in one control box. The input/output devices (I/O) can be integral with the controller or locatedremotely via a field network. Today’s controllers have extensive computational capabilities and, in additionto proportional, integral, and derivative (PID) control, can generally perform logic and sequential control.Modern DCSs support also neural networks and fuzzy application. DCSs may employ one or several

workstations and can be configured at the workstation or by an off-line personal computer. Localcommunication is handled by a control network with transmission over twisted pair, coaxial, or fiber opticcable. A server and/or applications processor may be included in the system for extra computational, datacollection, and reporting capability.

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Example PLC and DCS Projects:

• Installed the iFIX SCADA system at a large municipal filtration plant. The application had a about

2500 tags and several hundred screens. Existing Allen-Bradley PLC 5/40's were used for controls. Historical data was stored in MS SQL Server on a dedicated Historian PC and reportswere generated in Excel.

• Implemented operating controls for 2 freeze drying lines using Taylor Pro-Worx Plus Software,Modicon 984-130 Processor and Fix DMACS.

• Designed and implemented a plant control system for operation of the Heat Exchange Facility,part of a Lake Source Cooling Project. The control system is capable of being controlledremotely from Cornell University’s Central Heating Plant using a PC based NT operating platformrunning Intellution FIX V7.0 Full SCADA server with additional SQL/ODBC option installed.Remote communications was accomplished over an Ethernet backbone via user assignedTCP/IP addressing network scheme. Controls were implemented using a Quantum PLCprocessor, programmed with Concept IEC 1131-3, which offers Ladder Logic, Function Block,Sequential Function Chart, Structured Text, and Instruction List type programs.

• Designed and implemented system using three Modicon Quantum PLCs, and Five Wonderwareworkstations to control two Dual Fuel Furnaces with multiple burner controls as well asassociated equipment including baghouse, automatic spark arresting system, automatic hooddampers, stack caps and 300 HP ID fan.

• Recommended system components and replaced SCADA system for a network with 11 nodesand remote redundant SCADA capability communicating with 26 remote substations. AllenBradley PLC’s are used as the I/O nodes and Intellution FIX DMACS is the HMI software.

• Recommended system components and replaced complete SCADA system for a large water authority. Routinely perform ongoing upgrades and support for the Windows NT based SCADAsystem, which utilizes multiple Intellution SCADA nodes. It also includes remote SCADAcapability through the water authority WAN. The system employs radios and a leased digitalnetwork to communicate with over 25 remote substations and associated tanks. Substationcontrol is achieved using Allen-Bradley PLC's. The SCADA system includes data archiving for 

system analysis, alarming, reporting, and event and alarm-based emails and paging.• Provided installation of new instrumentation and controls to allow for the remote operation of two

(2) industrial water-pumping sites. In each of the locations, the pumps were locally controlled byAllen Bradley PLC’s, and then connected back to a central Provox DCS control room via 900MHzand 2Ghz radio links.

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WESTMEAD INTERNATIONAL SCHOOLCollege of Engineering & Architecture

Alangilan, Batangas City

In Partial Fulfillment of the Subject RequirementIn Industrial Automation

(ME Elec 4)

Submitted by:Geraldine A. Gupit

BSME – 511

Submitted to:Engr. Januh Pante

Instructor 

August 2, 2011

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