What is Distributed Control System (DCS)? Electrical Technology 08/24/2016 Communication, Communication, Controlling, Power System Leae a comment ! "iews Ta#le o$ Contents %&i'e %&i'e(( •
)hat is *istri#ute' Control System *CS+ o
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)hat is *CS System+ rchitecture o$ *istri#ute' *istri#ute' Control Control System
Engineering )or-station.
erating Station or &
Process Control 3nit o$ *CS
Communication System
Smart or ntelligent *eices
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)or-ing eration o$ *CS System
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*i$$erence #etween SC* an' *CS 5*CS s SC*
*CS Systems $rom *i$$erent "en'ors
What is Distributed Control System DCS? n recent years, the use o$ smart 'eices an' $iel' #uses ma-es distributed control system (DCS) to (DCS) to #e rominent in large an' comle7 in'ustrial rocesses as comare' to the $ormer centralie' control system9 This 'istri#ution o$ control system architecture aroun' the lant has le' to ro'uce more e$$icient ways to imroe relia#ility o$ control, rocess :uality a n' lant e$$iciency9 ;owa'ays, 'istri#ute' control system has #een $oun' in many in'ustrial $iel's such as chemical lants, oil an' gas in'ust in'ustrie ries, s, $oo' $oo' roces rocessin sing g units, units, nuclea nuclearr ower ower lants lants,, water water manage managemen mentt system systems, s, automo#ile in'ustries, etc9
What is DCS System? distributed control system (DCS) is a secially 'esigne' automate' control system that consists o$ geograhically 'istri#ute' control elements oer the lant or control area9 t 'i$$ers $rom the centralie' control system wherein a single controller at central location han'les the control $unction, #ut in *CS each rocess element or machine or grou o$ machines is controlle' #y a 'e'icate' controller9 *CS consists o$ a large num#er o$ local controllers in arious sections o$ lant control area an' are connecte' ia a high see' communication networ-9
n *CS control system, 'ata ac:uisition an' control $unctions are carrie' through a num#er o$ *CS controllers which are microrocessor #ase' units 'istri#ute' $unctionally an' geograhically oer the lant an' are situate' near area where control or 'ata gathering $unctions #eing er$orme' as shown in the $igure a#oe9 These controllers a#le to communicate among themseles an' also with other controllers li-e suerisory terminals, oerator terminals, historians, etc9
*istri#ute' in'ii'ual automatic controllers are connecte' to $iel' 'eices such as sensors an' actuators9 These controllers ensure the sharing o$ gathere' 'ata to other hierarchal controllers ia 'i$$erent $iel' #uses9 *i$$erent $iel' #uses or stan'ar' communication rotocols are use' $or esta#lishing the communication #etween the controllers9 Some o$ these inclu'e Pro$i#us, &ou may also rea'. )hat E7actly s Smart ?ri'+
Architecture of Distributed Control System s the name suggests, *CS has three main :ualities9 The $irst one is the 'istri#ution o$ arious control $unctions into relatiely small sets o$ su#systems, which are o$ semiautonomous, an' are interconnecte' through a high see' communication #us9 Some o$ these $unctions inclu'e 'ata ac:uisition, 'ata resentation, rocess control, rocess suerision, reorting in$ormation, storing an' retrieal o$ in$ormation9 The secon' attri#ute o$ *CS is the automation o$ manu$acturing rocess #y integrating a'ance' control strategies9 n' the thir' characteristic is the arranging the things as a system9 *CS organies the entire control structure as a single automation system where arious su#systems are uni$ie' through a roer comman' structure an' in$ormation $low9 These attri#utes o$ *CS can #e o#sere' in its architecture shown in the 'iagram #elow9 The #asic elements comrise' in a *CS inclu'e engineering wor-station, oerating station or &, rocess control unit or local control unit, smart 'eices, an' communication system9
Engineering Workstation: t is the suerisory controller oer the entire 'istri#ute' control system9 t can #e a PC or any other comuter that has 'e'icate' engineering so$tware 5$or e7amle, control #uil'er @ engineering station in case o$ AA $reelance 'istri#ute' control system9 This engineering station o$$ers ower$ul con$iguration tools that allow the user to er$orm engineering $unctions such as creating new loos, creating arious inut an' outut oints, mo'i$ying se:uential an' continuous control logic, con$iguring arious 'istri#ute' 'eices, rearing 'ocumentation $or each inut/outut 'eice, etc9
>ou may also rea'. )hat is P* Controller &ow it )or-s+
Oerating Station or !"# This is use' to oerate, monitor an' control lant arameters9 t can #e a PC or any other monitoring 'eice that has a searate so$tware tool on which oerator can iew rocess arameter alues an' accor'ingly to ta-e control action9 @or instance, it is a *igi"is so$tware tool that can run on a simle PC= enironment in case AA *CS9
erating stations can #e a single unit or multile units where a single unit er$orms $unctions li-e arameter alue 'islay, tren' 'islay, alarming, etc9 while multile units or PCs er$orms in'ii'ual $unctions such as some PCs 'islay arameters, some $or tren' archies, some $or 'ata logging an' ac:uiring, etc9
$rocess Control %nit of DCS t is also calle' as a local control unit, 'istri#ution controller, or rocess station9 'istri#ute' control system can consists o$ one or more rocess stations that can #e e7ten'e' with 'i$$erent tyes o$ / units9 These controllers consist o$ a ower$ul CP3 mo'ule, $iel' #us or communication mo'ule with e7ten'e' $iel' #us caa#ility an' either 'irect o r remote connecte' /s9 The $iel' 'eices li-e sensors an' actuators are connecte' to / mo'ules o$ this unit9 Some $iel' 'eices can #e 'irectly connecte' to $iel' #us 5such as Pro$i#us without any / mo'ule, which can #e terme' as smart $iel' 'eices9 These units ac:uire the in$ormation $rom arious sensors ia inut mo'ule, analye an' rocess it #ase' on the control logic imlemente' an' sen's the outut signals ia outut mo'ules to hae control on actuators an' relays9
n case o$ Brel no$ollowD a hre$Dhtt.//new9a##9com/control=systems/essential= automation/$reelance/controller/ac800$D targetDF#lan-DGAA *CS, C800@ mo'ule 5consi'er, $or instance acts as rocess station, which is resonsi#le $or ac:uiring an' controlling the 'ata $rom the rocess9 This unit consists o$ a ower suly along with CP3 section, Ethernet section, Pro$i#us section an' remote communication inter$ace unit $or /s inter$acing as shown in the $igure where $irst mo'ule is C 800@ unit an' other one is remote / 5also calle' as communication inter$ace mo'ule9 >u may also rea'. n erew o$ *C *ries
Communication System The communication me'ium lays a maHor role in the entire 'istri#ute' control system9 t interconnects the engineering station, oerating station, rocess station an' smart 'eices with one another9 t carries the in$ormation $rom one station to another9 The common communication rotocols use' in *CS inclu'e Ethernet, Pro$i#us, @oun'ation @iel' Aus, *eice;et, o'#us, etc9 t is not man'atory to use one rotocol $or entire *CS, some leels can use one networ- whereas some leels use 'i$$erent networ-9 @or instance, consi'er that $iel' 'eices, 'istri#ute' /s an' rocess station are interconnecte' with Pro$i#us while the communication among engineering station, & an' rocess station carrie' though Ethernet as shown in the $igure #elow9
The maHor a'antage o$ *CS is the re'un'ancy o$ some or all leels o$ the control area9 ost o$ the cases critical rocesses are installe' with re'un'ant controllers an' re'un'ant communication networ-s such that ro#lem in main rocessing line shoul' not a$$ect the monitoring an' control $unctions #ecause o$ the re'un'ant rocessing section9 >ou may also rea'. eriew o$ C *ries an' "@*
Smart or #ntelligent De&ices The intelligent $iel' 'eices an' $iel' #us technology are a'ance' $eatures o$ *CS technology that relaces tra'itional / su#systems 5/ mo'ules9 These smart 'eices em#e' the intelligence re:uire' $or simle sensing an' control techni:ues into the rimary sensing an' actuating 'eices9 n' hence it relaces the nee' $or a *CS controller to er$orm routine sensing an' control rocess9 These $iel' 'eices can #e 'irectly connecte' to $iel' #us so that sourcing o$ multile measurements to the ne7t higher leel control station is ossi#le ia 'igital transmission line #y eliminating e7traneous har'ware such as local / mo'ules an' controllers9
Working ' Oeration of DCS System The oeration o$ *CS goes li-e thisI Sensors senses the rocess in$ormation an' sen' it to the local / mo'ules, to which actuators are also connecte' so as to control the rocess arameters9 The in$ormation or 'ata $rom these remote mo'ules is gathere' to the rocess control unit ia $iel' #us9 $ smart $iel' 'eices are use', the sense' in$ormation 'irectly trans$erre' to rocess control unit ia $iel' #us9
The collecte' in$ormation is $urther rocesse', analye' an' ro'uces the outut results #ase' on the control logic imlemente' in the controller9 The results or control actions are then carrie' to the actuator 'eices ia $iel' #us9 The *CS con$iguring, commissioning an' control logic imlementation are carrie' at the engineering station as mentione' earlier9 The oerator a#le to iew an' sen' control actions manually at oeration stations9 you may also rea'. Power *istri#ution in n'ustries
Difference beteen SCADA and DCS (DCS &s SCADA) lthough #oth *CS an' SC* are monitoring an' control mechanisms in in'ustrial installations, they hae 'i$$erent goals9 There e7ist some commonality #etween *CS an' SC* in terms o$ har'ware an' its comonents, howeer, there are certain re:uirements #y the en' alications that searates a ro#ust an' cost=e$$ectie *CS $rom the ia#le SC* system9 Some o$ the 'i$$erences #etween *CS an'
SC* are liste' #elow9
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*CS is rocess oriente', whereas SC* is 'ata=gathering oriente'9 *CS emhasies more on control o$ the rocess an' it also consists o$ suerisory control leel9 n' as a art o$ 'oing so, it resents the in$ormation to the oerator9 n the other han', SC* concentrates more on ac:uisition rocess 'ata an' resenting it to the oerators an' control centre9
29 n *CS, 'ata ac:uisition an' control mo'ules or controllers are usually locate' within a more con$ine' area an' the communication #etween arious 'istri#ute' control units carrie' ia a local area networ-9 SC* generally coers larger geograhical areas that use 'i$$erent communication systems which are generally less relia#le than a local area networ-9 J9
*CS emloys a close' loo control at rocess control station an' at remote terminal units9 Aut in case o$ SC* there is no such close' loo control9
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*CS is rocess state 'rien where it scans the rocess in regular #asis an' 'islays the results to the oerator, een on 'eman'9 n the other han', SC* is eent 'rien where it 'oes not scan the rocess se:uentially, #ut it waits $or an eent that cause rocess arameter to trigger certain actions9 &ence, *CS 'oes not -ee a 'ata#ase o$ rocess arameter alues as it always in connection with its 'ata source, whereas SC* maintains a 'ata#ase to log the arameter alues which can #e $urther retriee' $or oerator 'islay an' this ma-es the SC* to resent the last recor'e' alues i$ the #ase station una#le to get the new alues $rom a remote location9
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n terms o$ alications, *CS is use' $or installations within a con$ine' area, li-e a single lant or $actory an' $or a comle7 control rocesses9 Some o$ the alication areas o$ *CS inclu'e chemical lants, ower generating stations, harmaceutical manu$acturing, oil an' gas in'ustries, etc9 n the other han' SC* is use' $or much larger geograhical locations such as water management systems, ower transmission an' 'istri#ution control, transort alications an' small manu$acturing an' rocess in'ustries9
n site o$ these maHor 'i$$erences, the mo'ern *CS an' SC* systems come with common stan'ar' $acilities while 'ealing rocess lant automation9 &oweer, the choice #etween *CS an' SC* 'een's on its client an' en' alication re:uirement9 Aut i$ the client choice #etween these two, #y gaining e:ual re:uirement $rom the rocess, *CS is the economical choice as it hel to re'uce the cost an' o$$er #etter control9
DCS Systems from Different endors Some o$ the aaila#le *CS systems inclu'e •
AA= @reelance 800@ an' 800 7
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>o-ogawa= Centum CS J000 an' 1000
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&oneywell=T*C J000
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Emerson= *elta " *igital utomation
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Siemens= Simatic PCS
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llen= Ara'ley= ;etLin7
*ear engineers an' rea'ers, we hoe the $urnishe' 'ata is in$ormatie $or you9 $ you are wor-ing with *CS or any other automation technologies or you might hae -nown something a#out *CS, lease 'o not hesitate to share your e7erience with *CS in the comment section #elow as it woul' hel$ul $or rea'ers9 )e woul' li-e to hear $rom you9 s it woul' hel$ul $or rea'ers9 )e woul' li-e to hear $rom you9
