Conversion of CIRED paper into a feature article
Self-healing power distribution through zoning
In this article, Pekka MANNER, Kari KOIVURANTA, Antti KOSTIAINEN and Göran WIKLUND of ABB PPMV look at how the concept of zoning – a systematic method of dividing distribution networks into manageable areas based on loads, load criticality and disturbance vulnerability – can help improve reliability through the use of intelligent network nodes which cooperate seamlessly with substation and control centre systems. System self-healing is nothing new in power distribution networks, where auto- reclosing and auto-reclosers have been used for decades – traditionally at the individual feeder level. With increasing demands for uninterrupted power from an ever- growing group of consumers, however, operators need a broader view of the whole distribution network and its capability to limit the impact of disturbances to as small areas and as few consumers as possible. Dividing distribution networks into zones, separated by active and intelligent components, enables fault situations to be handled in an optimal way. Optimal in this context means as few affected consumers as possible, fast power restoration and with the involvement of as few personnel as possible. Central to this zoning concept are active and intelligent node components, data communication between these nodes and the substation, and control centre systems with appropriate software. The fast development of technology in these areas – especially in communications – means it is now feasible to build advanced applications for zoning of this kind. This is particularly important for power utilities, as they face increasing demands for more reliable power supply and lower operational costs.
The zone concept The structure of the power distribution network is influenced by population density, power consumption levels, the criticality of supply, legislation, environmental concerns, weather conditions, and the philosophy of the distribution network owner, among other factors. For distribution network operators, the need to improve supply reliability and voltage quality, and to improve operational efficiency, are key drivers. In addition, the growing use of distributed, alternative energy sources makes network operation more complex, but also provides additional means to secure the power supply. All these factors make zoning a useful model for planning and upgrading distribution networks. Figure 1 shows the various zones downstream of the substation as shaded areas. Located between these zones are zone dividers with protection and breaking/reclosing or simple disconnection capabilities. All zone dividers have facilities for remote communication to transmit the status indications, control commands, measurements, and so on, required by the application. Depending on the capabilities of the zone divider equipment, the zone on the downside is either a protection zone or a control zone. C I R E D 21st International Conference on Electricity Distribution Frankfurt, 6-9 J une 2011
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TOWARDS SELF-HEALING POWER DISTRIBUTION BY MEANS OF THE ZONE CONCEPT
Pekka MANNER Kari KOIVURANTA Antti KOSTIAINEN Göran WIKLUND Fortum Oyj – Finland Fortum Oyj – Finland ABB Oy – Finland ABB Oy – Finland [email protected] [email protected] [email protected] [email protected]
ABSTRACT This paper presents the zone concept, a systematic method of dividing distribution networks into manageable areas based on loads, load criticality and disturbance vulnerability. The self-healing functionality is achieved by utilizing intelligent network nodes and their seamless cooperation with substation and control centre systems. The paper presents a real case where the planning considerations are described.
INTRODUCTION System self-healing is not a new issue in the field of power distribution, where auto-reclosing and auto-reclosers have been used for decades. In the past, however, self-healing was dealt with on the individual feeder level. With the increasing demand of uninterrupted power urged for by an FigureFig u1.re Main 1: M principlesain pri nofc zoning.iples of the zone concept ever growing group of consumers, it is necessary to have a broader view of the whole distribution network and its Figure 1 shows the various zones downstream of the Protection and control zones capability to limit the impact of disturbances to as small substation as shadowed areas. Between these zones zone The zone borders are located according to the capability of the zone dividers, the areas and as few consumers as possible. differencesdivide rins faultwi tvulnerabilityh protec tbetweenion an thed areasbreak andin gthe/r eclcriticalityosin gof theor poweronly The Zone concept provides a model for dividing supplydisc withinonne thect iareas.ng ca Forpa biexample,lities aareasre l occana tbeed. differentiated All zone according divider sto a faultre probability,provide ord the w needith tofa secureciliti ethes supplyfor r toem areasote withcom substantialmunic aand/ortion criticalfor distribution networks into zones, separated by active and consumption. The same criteria are used when determining whether a zone should be intelligent components, in order to handle fault situations in a protectiontransfer zone o for a controlstatus zone. indications, control commands, an optional way. Optimal in this context means as few Circuitme abreakerssureme andnt sdisconnectors, etc. requ iarered naturally by the among appl itheca mosttion .essential Depen componentsding affected consumers as possible, fast power restoration and, in onthe distributionthe capab network.ility o However,f the zo nbasede di vonid theer needequ itop msecureent tthehe supply zone and on reducethe dlossesown thereside isis also eith ane rincreasing a prote usecti ofon distributed zone or compensation a control equipment.zone. finally, as little need of personnel as possible. The active Furthermore, there is, partly based on the need to have easy access and weather and intelligent node components, the data communication protection,Today anth increasede ongoi nneedg in toc rhaveeas eground of di mountedstribut eequipment,d energy even res oif utherc networkes between these nodes and the substation, and the control otherwiseput spe is builtcial as de anm overheadands on line tnetwork.he flexibility of the equipment centre systems with appropriate software form the corner In futhen applicationctionalit iny Figureand a 2d theap tsecondaryability. equipment housed in a weather-proof enclosure is pole-mounted close to the ground level. The equipment handles stones of the Zone concept. protection, auto- reclosing, control and carries out versatile measurements. The fast development of especially feasible communication CommunicationDividing withne antw upperork levels i nsystemto P isr requiredotect iino norder a nto dgain Co the nfulltr ol technologies have made it possible to build the needed advantagezones of the automation. applications. This is particularly important for power The capability of the zone dividers, the differences in fault utilities, as they are faced with the increasing demand for a vulnerability between the areas and the criticality of the more reliable power supply and lower operational costs. consumption within the areas are main issues for defining zone border locations. Needless to say that differentiating THE ZONE CONCEPT areas with low fault probability from those with high fault risks is worthwhile. Another zone divider criterion is the The lay-out of the power distribution network is affected by need to secure the supply to areas with substantial and/or the density of settlement, power consumption and its critical consumption. The same criteria are used when criticality, legislation, environmental concerns, weather determining whether a zone shall become a protection zone conditions, philosophy of the distribution network owner or a control zone. etc. Dominating driving forces today are the needs to improve the supply reliability and voltage quality as well Primary components, i. e. zone dividers as the requirement to improve the operational efficiency Circuit breakers and disconnectors are naturally among the of the network company. Additionally, the increased use of most essential components in the distribution network. distributed energy resources complicates the network However, based on the need to secure the supply and reduce operation but it also provides additional means to secure the losses there is also an increasing use of distributed power supply. In such a situation the zone concept will compensation equipment. Furthermore, there is, partly provide a useful model for planning and upgrading of based on the need to have easy access and weather distribution networks. protection, an increased need to have ground mounted
Paper No 0622 1/4 C I R E D 21st International Conference on Electricity Distribution Frankfurt, 6-9 J une 2011
Paper 0622 C I R E D 21st International Conference on Electricity Distribution Frankfurt, 6-9 J une 2011 equipment, even if the network otherwise is built as an Paper 0622 overhead line network.
equipment, even if the network otherwise is built as an overhead line network. Recloser Station
Load Break Switch Load Break Switch Station Station Recloser Station
Load Break Switch Load Break Switch Station Station
Figure 4: Principle location of the Recloser Stations and the Load Figure 2: Traditional mounting of vacuum circuit breaker in an Bre ak Switch Stations in a main feeder oFigureverhead l2.ine Traditional distribution n emountingtwork. (Pole -ofmo vacuumunted Recl ocircuitser) breaker in an overhead line distribution network (pole-mounted recloser). Se condary components, i.e. intelligent zone dividers In the application in Figure 2 the secondary equipment WiFigtuhre th 4e: dPerivnecliopplem loecnatt ioofn e olfe tchter oRenicclso site rh Satsa btieoenns apndos tsheib lLeoa tod hoFiusguered 2in: Ta rawediatitohnearl- prmooofunt einngc loosf vuarceu iusm pol cierc-umoit burentaekde rc lion saen prBreovaikde S wigtcrhid S taditiosntrsi buin ate md ains efeceondedar ry equipment with too vtherhe geardo ulinnde ledivsteril.b Tuthioen e nqeutiwpomrke.n (Pt hoalned-mleosu pnrteotde cRtieclono, saer)uto - en hanced functionality. In addition to protection, versatile reFigure closing 3, c showsontrol a nad weather-proofcarries out versa tsolution,ile measur ewhichments. is especiallymeSeacsoundare mesuitableryn tcso mspou pwhennepontrtisn, g morei .e.b iontth ethan lliogpeent ra ztioonen dianvdide arss et CooneInm thm circuiteu naipcpaltii cobreakerant iwonit hin a n Fiis ug puneededpre r 2l ethveel atsyse stctheoenmd sameairsy r eeqquu ilocation.ipremd ein t ThismaWi ntypetahg tehmee of dne tvsolution ealroep pmroenv tiis doe fdtypically e.l eLcotrcoanl iac ns dit rheamos bteee nc opnotsrsoilb laen tdo orusedhodeusr et odwhen igna ian we t htheea tfhu elmainrl- aprdvoofa nfeeder teangcel osofu hastrhee i sa upoltotom bee-amot ibranchedonun. ted close off intoaupr twotovomideat feeders.i ong freatid urdi esThes tasribu w secondaryteledl as scoecmonmdau nryicat eioqun iapmnde anutx ilwiairtyh equipmentto the ground haslevel. versatile The equip mfunctionalityent handles pr ofortec tprotection,ion, auto- auto-reclosing,fuennhcantiocedns a frue nactls iocontrolo nfoaluintyd. i Inandn t hadesd ei t“ialonl -tino -ponrote eunictitons”., Tvherussa tthilee communication.reclosing, control and carries out versatile measurements. zomenea sduirveimedersnt cs ans buep pseolreticntegd abnodt hp roovpideeradt wiointh eaxnadc tlya sthset Communication with an upper level system is required in fumancntaiogneamelitnyt caornes ipdreorveidd evdia. bLleo.c al and remote control and order to gain the full advantage of the automation. automation features as well as communication and auxiliary Cofunmcmtiounnsi acraet iaolnso found in these “all-in-one units”. Thus the Cozomnem duivnidcaetrsio cna ins bae c seenltercatle pda artn odf p trohev zidoende cwointhc epxta,c atsly i tt hise esfusnencttiioaln atoli tkyn coown stihdee rsetatd uvsia obfl et.h e zone divider equipment an d to control it. With the development of capable wireless coCommmmunuincaticiaotnio ni t has become feasible to arrange coCommmmuunnicaticaitoionn tios am coenstt raolf p athrte o fn tohdees zo nine cao ndciesptrti,b aust iiot nis neestswenotrik.al Ttohi ksn haows bthee ns tmataudse o pf othssei bzolen bey d tihevid dere veeqluoippmmeenntt ofan dpu tobl coicn twroilr eitl.e Wss ithn etthwe ordevksel. oIpnm tenhet osfe claepcatibonle wofir elethses cocommmmuunniicatcatiioonn metit hohdass nobt ecoonlym ec omfeasmuinbiclea tioton fearartuanregse bucotm amlsuon icataviaoilna bitoli tym oasnt do fs etchue rintyo desiss uiens ah adviset ritbou tibeon adnedtrwesosredk. .T his has been made possible by the development
Figure 3: Ground mounted vacuum circuit-breaker application of public wireless networks. In the selection of the with one incomer and two outgoing feeders (Recloser Station). Subscommtautinoicatn aindon cmoetnthroodls c neontt roen lyso fctowmamreu nication features The network is either an overhead or a cable network. Asbu ts aiadl sion thaev abielagbiinlnitiyn g aloncda l saeuctuormitayt ioinss huaess beheanv ea ptaor t obef thade ddresistrsedibu. tio n network for quite some time. The deve-
ThFigeu arep p3l:i cGarotiounn di nm Fiougnuterde 3va iscu uumse dci rcwuhiet-nb rea awkeera athpeprlipcraotioofn lo pment of communication and the need to have an soFigurewliuthti one i 3.sin rc eGround-mountedoqmueire adn,d a tnwdo it o isut geosipneg c vacuumfiaeellyde rsfe a(Rsib ecircuitclelo swehr eS nbreakerta mtiorne). applicationimSubsprotvaetdio owithnv aendrv ieone cwo nta incomernrdo l ccoennttrroe land soof ftht wea wreh ole distribution thtwoTahne o noutgoingnetew coirrkc uisit e bi tfeedersrheear kaenr o(vre rhf(r. ereclosereadc loors ea rc ina bstation lFie ngeutrweo ),2rk) for.i s n eeithereded overheadneAstw soair dkor ifn r cableothme btheeg network. icnonntinrgo llo ceantl aruetso mgaavetio rni shea st ob eceennt ar aplairzte odf at the same location. A typical situation like this is when the cothnet rdoisl antribdu autiotonm natetwiono.r Tk hfeo rlat qesuitet d evsoelmoep mtimenet. hTash em addeev eit- maThien afepepdliecra htiaosn tion bFie gburraen c3h eisd uosfefd i nwtoh etnw oa fweeadtheres.rp Trohoef poslopsmiblente too floc caotme msuunich cfautnioctni onaandlit yt heals one toe dth et os uhabstavetio ann sesoclountdioanr yi s reeqquuiipremde, natn d hita sis evseprescaiatillyle fefuansibctileo nwahlietyn mfoorre leimvepl.ro ved overview and control of the whole distribution prAlternatively,thotanec otnione c, iracuutoit- rebarc eground-mountedlaokseinr g(r, ecfo. nretroclol saenrd in c oFiair-insulatedmgmuruen 2ic) aisti onene. dload-breaked net wswitchork fro mapplication the control withcentr eones ga ve rise to centralized incomerat the sam eand locat twoion. Aoutgoing typical si tfeedersuation lik e(load-break this is when t hswitche Instation)co nthtreo lt any pcande auo ftbeo msy atsused.tieomn. Ts hFigureoew latn esint d4Fiev geluorep m5en cot hnastr oml aanded it Alillustratesmateirnn afetievdeelyr an,h aa sgapplication troo ubned b-moranucnh tewithedd oafi frboth -iinntsou latrecloserwteod f eloeadder- brs.and eTahk eload-break aupostosmibl atswitcheio tno lfocu nstations.acttei osnusc h arfu eLoad-breakn cttoion baeli tyfo aulsn od toat th be ostuhb sltaocaltion, swswitchesseictochn dapryp lcaniceaqtuio ibepnm w eusednitth ohan furtherse ivnecrosma touteilre a ninfdu nthetcwtio network,noaulittgyo infogr and thesulebv seload-breaktl.a t ion and co ncapabilitiestrol centre le vareels. A system which takes in to account the existing loads at various locations and the feespeciallypreotdeercst (ionLo,a ad uuseful-brto-ereakc ls oinwsi tnnetworkcgh, Sctoantiotron l)reconfiguration aisn du sceodm. Fimguunricea 4t iso hsituations.no.w s As the load-break switch station an application with both recloser and load-break switch suInp ptlhye ctaypaeb iolift ys yosfte mal tesrhnoawtinv e inn eFitwgourrke c5o ncofignutrroalt ioannsd stisAla tprovidedtieornns.a tLivoaeldy -, withbra egark othe suwndi t-samecmohesu ncant esecondaryd b aei ur-sineds uflaurtet hequipmentder lo oaudt -ibrn tehaek as themaau recloserktoems atit iopno sstation,sfiubnlect tio ni smpextensive arleeme ton t bfae s t,f ofulnldy aatut obmaotthi c lfoacalult, nemeasurementsswtwitocrhk apndpl tiheca tlioan dand -wbriteh acontrol ko cnaep ainbc ilcapabilitiesoitmiees ra raen eds ptewc ioarea lloyu utavailable.gseofiunlg losucbasliztaatitioonn a, nfda uclto nistrolal ctioennt,r en leetwveolsr.k A r escyosntefmig uwrahtioichn taakneds infe endeetwrso (rLko raedc-obrnefigaku srwatioitcnh Ssitutataiotion)n iss. uAsesd .th Fieg lourade 4- brsheoawks powintoe ar crceostuornta thtione e fxuinstcitnigon loalaidtys, ait.e v. atroi ocrueats loec a tsioelnfs- heanadli tnghe swani tcaph plsticatatiioonn wiis thp rboovtihd erde clwoistehr athned lsaoamd-ebr eseacko snwdaitrcyh powsupperly di csatrpibuabitilionty noeft waorltekr.n ative network configurations eqstuaitpiomnens. Lt oaas dth-bre ereacklo swseirtc shtaestio cann e bxete unssediv ef umrtehaersu oruetm inen ttshe makes it possible to implement fast, fully automatic fault annedt wcoonrktr oandl cap theab loilaitdies-br areaek av caaipalabbillie.tie s are especially useful localization, fault isolation, network reconfiguration and in network reconfiguration situations. As the load-break power restoration functionality, i.e. to create a self-healing switch station is provided with the same secondary power distribution network. equipment as the recloser station extensive measurements Paanpde rco Nno t0ro62l 2cap abilities are available. 2/4
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equipment, even if the network otherwise is built as an overhead line network.
Recloser Station
Load Break Switch Load Break Switch Station Station
Figure 4: Principle location of the Recloser Stations and the Load Figure 2: Traditional mounting of vacuum circuit breaker in an Break Switch Stations in a main feeder overhead line distribution network. (Pole-mounted Recloser) Figure 4. Principle location of recloser stations and load break switch stations in a main feeder.Secondary components, i.e. intelligent zone dividers In the application in Figure 2 the secondary equipment With the development of electronics it has been possible to housed in a weather-proof enclosure is pole-mounted close provide grid distributed secondary equipment with to the ground level. The equipment handles protection, auto- Intelligentenhanced fzoneuncti odividersnality. In addition to protection, versatile reclosing, control and carries out versatile measurements. measurements supporting both operation and asset Communication with an upper level system is required in Continuingmanageme technologynt are prov improvementsided. Local an haved remo enabledte con ttherol developmentand of grid distributed order to gain the full advantage of the automation. secondaryautomatio nequipment features as with wel enhancedl as comm ufunctionalitynication an d– a providinguxiliary versatile measurement capabilitiesfunctions a rthate al ssupporto found both in th operationese “all-in and-one asset units ”.management, Thus the for example – in additionzone di vtoid protection.ers can be sLocalelecte andd an remoted provi dcontroled wit hand exa automationctly the features, as well as communicationfunctionality c oandnsid auxiliaryered via bfunctions,le. are also provided in these all-in-one units. Zone dividers can be provided with exactly the right functionality for the application.
CommunicationCommunicatio isn a central part of the zoning concept, as it is essential to know the statusComm ofu ntheica tzoneion i sdivider a cent requipmental part of t hande zo tone control concep it.t, Withas it ithes development of highly capable,essential widely to kno available,w the stat reliableus of th eand zo nsecuree divid publicer equ wirelessipment networks, it is now feasibleand to co ton implementtrol it. Wit hcommunication the developmen capabilitiest of capab lein wmostirele nodesss in a distribution network.commun ication it has become feasible to arrange communication to most of the nodes in a distribution Substationnetwork. T hiands ha controls been mcentreade p osoftwaressible by the development Whileof pu localblic automationwireless n hasetw orbeenks. aI npart th eof thesele distributionction of t hnetworke for some time, the developmentcommunicat iofon communication methods not o nandly c theom mneedunic foratio improvedn feature soverview and control of the wholebut a distributionlso availa binetworklity an hasd s egivencurit yrise is tosu ecentralizeds have to control be and automation. The latestaddres developmentssed. enable such functionality to be located at the substation level as
Figure 3: Ground mounted vacuum circuit-breaker application well. with one incomer and two outgoing feeders (Recloser Station). InSubs the tsystemation a shownnd cont inr oFigurel cent r5,e controlsoftwa andre automation functions are located at local, The network is either an overhead or a cable network. substationAs said in andthe b controleginni ncentreg loca llevels. autom Aat systemion has bthateen takes a par tinto of account the existing loads atth variouse distrib locationsution ne twandor thek f osupplyr quite capability some tim ofe .alternative The deve network- configurations The application in Figure 3 is used when a weatherproof enableslopment the o fimplementation communicatio ofn fast,and fullythe automaticneed to faulthave localization, an fault isolation, solution is required, and it is especially feasible when more networkimprov ereconfigurationd overview an dand co npowertrol o restorationf the whole functionality distributio n– that is, the creation of a than one circuit breaker (ref. recloser in Figure 2) is needed self-healingnetwork fro powerm the distributioncontrol ce ntnetwork.res gave rise to centralized at the same location. A typical situation like this is when the control and automation. The latest development has made it main feeder has to be branched off into two feeders. The possible to locate such functionality also to the substation secondary equipment has versatile functionality for level. protection, auto-reclosing, control and communication. In the type of system shown in Figure 5 control and Alternatively, a ground-mounted air-insulated load-break automation functions are to be found at both local, switch application with one incomer and two outgoing substation and control centre levels. A system which takes feeders (Load-break switch Station) is used. Figure 4 shows into account the existing loads at various locations and the an application with both recloser and load-break switch supply capability of alternative network configurations stations. Load-break switches can be used further out in the makes it possible to implement fast, fully automatic fault network and the load-break capabilities are especially useful localization, fault isolation, network reconfiguration and in network reconfiguration situations. As the load-break power restoration functionality, i.e. to create a self-healing switch station is provided with the same secondary power distribution network. equipment as the recloser station extensive measurements and control capabilities are available.
Paper No 0622 2/4 C I R E D 21st International Conference on Electricity Distribution Frankfurt, 6-9 J une 2011
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The DMS system can provide both the number of outages and their duration. Based on this historical data, as well as the fault probability based LuoVa analysis, the zone borders were determined for the Kirkkonummi pilot installation.
Divisions into zones and selection of zone dividers The piloted feeders have been divided to 20 remote controlled disconnector protected areas and 2 remote controlled recloser areas.
FFigureigure 5. 5 Automation: Autom functionalityation fun atc tdifferentionali tlocationsy at d iinf fae distributionrent loc anetwork.tions in a distribution network Pilot network THThis Ezoning PI conceptLOT is CAS being pilotedE on two rural area feeders in Kirkkonummi, Finland. The pilot project is divided into three phases. In the first phase, four new disconnectors and two new reclosers were installed into the distribution network and a local substation system into the primary substation. The devices are equipped with current Thsensors,e co whichncep cant i ssupply bei ndatag pforil theot elocald on substation two rsystemural andare fora thefee distributionders in Kimanagementrkkonum system,mi, F forin determiningland. Th faulte t alocations.rget o fThe th locationse pilot forp rtheoj enewct devicesis to were decided using feasibility calculations made with LuoVa, ABB's reliability analysis vesoftware,rify t heand fonunc thet basisiona ofl ihistoricalty of t hefault cdata.oncept. The pilot project is Figure 7: Protection areas of the piloted feeders. Red zones diInv theide secondd in phase, thr theee pilotph isa scheduledses. In to coverthe otherfir sfeederst ph ofa sthee, same4 new indicate disconnector protected areas and blue zones recloser disubstation.sconne Inc theto rthirds an phase,d 2 an neighbouringew reclos substationers ar ise duein stot albel includeded int ointo th thee areas. dipilotstr soibu thatti onthe co-operationnetwork andand back-up a loc functionalitiesal substa tcanio nbe s tested.ystem into the The original target is, besides verifying the functionality, to reduce the System Average prInterruptionimary Durationsubs Indextatio (SAIDI)n. T –h thee totalde vdurationices ofa interruptionsre equip top theed average with The feasibility of the concept pilot was analyzed with cucustomerrren t– bysen 50 spercent.ors, whCurrentlyich theca SAIDIn su isp aboveply 200da tina the f oarea,r t evenhe thoughlocal LuoVa, ABB's reliability analysis software. The program the automation level is quite high. substation system and for the distribution management calculates Customer Interruption Costs (CIC). Based on the To find the most suitable locations for the zone dividers (breakers and switches), the syteamste usedm, bothfor thede LuoVaterm reliabilityining fanalysisault l ocsoftwareatio nands. theTh historicale loca outage/faulttions fo r Finnish regulation model 50% of the reduced disturbance thstatisticse new from d ethevic DMSes distributionwere d enetworkcided management by feas ibsystem.ility calculations costs can be regarded as regulation income for the The DMS system can provide both the number of outages and their duration. Based on distribution company. mathisd historicale with data, Lu oasV wella, asA theBB fault's rprobabilityeliabili fromty a LuoVanaly sanalysis,is sof tthew azonere and onborders the werebas idetermineds of his tforor theic aKirkkonummil fault da pilotta. installation. The results show that the phase 1 would pay off after 6 In the second phase the pilot is scheduled to also cover years, with an interest rate of 8%. The asset-based income, other feeders of the same substation. In the third phase also allowed by Finnish regulation was not taken into account in a neighbouring substation is due to be included into the pilot the calculations, since there are no regulation definitions for so that the co-operation and backup functionalities would smart grid related new devices. With asset based income, also be tested. the pay-back time would be even shorter. Nor does the program take SAIFI reduction into account. Background and objectives The original target is, besides verifying the functionality, to Table 1: Feasibility of the concept pilot investments reduce the SAIDI index by 50%. Currently the SAIDI is Years Total CIC Investment, Profitability, above 200 in the area, even though the automation level in savings, k€ k€ k€ the area is quite high. 1 28 134 -106
The determination of the most suitable locations for the 2 55 134 -80 zone dividers, i.e. breakers and switches, was done using 3 79 134 -56 both the earlier described LuoVa reliability analysis 4 101 134 -33 software and historical outage/fault statistics from the DMS system. 5 122 134 -12 6 142 134 7 7 159 134 25
Choices of communication means The network automation devices use the public network (GPRS) for communication with the substation computer. The substation computer communicates with the SCADA system, which is cooperating with the DMS systems. The
Figure 6: Example of historical data available from the DMS coverage of the public network was measured in the planned system. The figure shows the outages in 2009 for all transformer disconnector and recloser locations for verification of the districts, fault test switching included. availability of the network. Since the communication
Paper No 0622 3/4 The piloted feeders have been divided into 20 remote-controlled disconnector protected areas and two remote-controlled recloser areas. The feasibility of the concept pilot was also analysed with LuoVa, which was used to calculate customer interruption costs (CIC). Based on the Finnish regulation model, 50% of the reduced disturbance costs can be regarded as regulation income for the distribution company. The results show that the first phase would achieve payback in six years (at an interest rate of 8 percent). The asset-based income allowed by Finnish regulation was not taken into account in the calculations, since there are no regulation definitions for new smart grid-related devices. With asset-based income, the payback time would be even shorter. The program does not take System Average Interruption Frequency Index (SAIFI) reduction into account either.
Choice of communications The network automation devices use the public mobile network (GSM/GPRS) for communication with the substation computer. The substation computer communicates with the SCADA system, which cooperates with the DMS systems. The coverage of the public network was measured in the planned disconnector and recloser locations for verification of the availability of the network. Since the communication network depends on power supplied from the distribution network, it is important that there are several communication link stations available for the network automation devices, and that some of the link stations are supplied from a different distribution feeder.
Fault localization Experience from other distribution network operators shows that the main challenge in automatic fault localization is to get the location of the fault with high accuracy. The reason for this is most likely that the majority of the faults in the network are earth faults, which cannot be located with earlier equipment. In the pilot installation this problem has been addressed as follows. First, an intelligent fault location package for the DMS has been developed for the substation. This package includes: Localization of earth faults using new algorithms and graphical methods Disconnectors provided with current transformers, used as fault indicators Utilization of the fault indicator information in the DMS fault localization functions Triggering of the fault recorder including the Fault Locator (FLOC) function and combining it with the protection start signals. This enables possible fault locations are delivered to the DMS system before the faults cause an auto- reclose function and/or breaker trip. Second, the DMS system will be provided with additional functionality, including: Localization of auto-reclosings (for example, all auto-reclosings in a week will be localized simultaneously) Display of the auto-reclosing frequency by feeder and by time period. Calculation of the FLOC parameters. Automatic fault detection, isolation and restoration (FDIR) For FDIR, the DMS system performs the following operation sequence. The SCADA system provides the DMS system with the 'fault package' and the status of possible fault indicators. The DMS system locates the fault and creates a switching sequence for isolation of the fault and for restoration of the power supply using alternative supply routes (back-feed). The switching sequence is sent to the SCADA system for realization and the SCADA system implements it automatically. This is done step by step: the sequence does not proceed to the next step until the position indication has been received from the switching device. Tripping of a breaker during the sequence will stop the sequence. One key question is where to locate the FDIR functionality. In the first phase of the pilot installation, the DMS system was central to providing FDIR functionality. The DMS system provides accurate and reliable information about the network situation. When a switching sequence is created, factors such as network loads, open connections, occasional earthings and ongoing construction work have to be taken into account. Solutions in networks including Distributed Energy Resources (DER) and demanding data maintenance issues are somewhat easier to handle in a reliable and dependable way in the centralized DMS system. In the second phase of the pilot, however, the feasibility of running the FDIR functionality in the substation system is being tested. With this decentralized DMS/FDIR approach, the central system does not need to be directly involved in the process related to a specific substation. The feasibility of such a solution depends on the capabilities of the selected systems and their ability to work together.
Conclusion The ability of the system to locate earth faults with high enough accuracy is a key issue when striving to reduce SAIDI figures. The reduction can be achieved when the fault locator functionality of modern protection relays is combined with information from network distributed fault indicators. With a DMS system that can create reliable switching sequences automatically and cooperate with the SCADA systems in place, further improvements will be focused on the division of the network into zones and the selection of the zone dividers. Another key issue is the quantity and quality of the data transferred to the control centre. Advanced station-level fault management reduces the quantity and improves the quality of the data sent to the operators. This enables the control centre to focus on more important issues and overall coordination tasks. The payback period of the pilot project is expected to be six years. The zoning concept is being piloted in a network that already has a relatively high level of automation. The payback period would be even shorter in a network with a lower automation level. The creation of such zoned distribution networks is one of the first key steps towards an automated, self-healing network.
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