Integration of modelling and monitoring to optimize network control: two case studies from Lisbon

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1 Aville online t ScienceDirect Procedi Engineering 70 ( 2014 ) th Interntionl Conference on Computing nd Control for the Wter Industry, CCWI2013 Integrtion of modelling nd monitoring to optimize network control: two cse studies from Lison N. Dis, *, N. Ferreir, A. Donnelly EPAL, S.A, Av. Berlim, 15, Liso, Portugl Astrct In recent yers, EPAL, Portugl s lrgest wter supply compny, hs successfully implemented projects for optimizing control of the Lison distriution network, which include the implementtion of network monitoring project (WONE) imed t reducing wter losses, s well s the development of n EPANET sed ll-pipe hydrulic network model. Building on the individul success of ech of these projects, the integrtion of these two se tools hs proved to e extremely useful s regrds mnging situtions of gret complexity, s demonstrted in the two cse studies tht re presented in this pper The Authors. Pulished y Elsevier Ltd. Open ccess under CC BY-NC-ND license. Selection nd peer-review under responsiility of the CCWI2013 Committee. Keywords: Modelling; Monitoring; Network control 1. EPAL s wter supply system nd distriution network EPAL - Empres Portugues ds Águs Livres, S.A. is the successor to the CAL - Wter Compny of Lison, concession for wter supply to the city of Lison from 1868 to Octoer 1974, when the concession contrct finished nd when EPAL ws formed. EPAL strcts, trets, trnsports nd distriutes wter for humn consumption through the mngement nd opertion of its supply system tht encompsses round 740 km of mins from the Cstelo de Bode reservoir to severl municiplities. Among its min production nd trnsport infrstructure, the compny hs three min * Corresponding uthor. Tel.: ; fx: E-mil ddress: nunodis@epl.pt The Authors. Pulished y Elsevier Ltd. Open ccess under CC BY-NC-ND license. Selection nd peer-review under responsiility of the CCWI2013 Committee doi: /j.proeng

2 556 N. Dis et l. / Procedi Engineering 70 ( 2014 ) susystems, whose dily production cpcity mounts to 1,017 million m 3 : Alviel Aqueduct in opertion since 1880; Tejo Aqueduct opened in the 1940s nd Cstelo do Bode susystem in opertion since EPAL supplies out qurter of Portugl s popultion, living in 34 municiplities on the north side of the Tgus River, which corresponds to totl re of 7,005 km 2. In Lison, EPAL is lso responsile for wter distriution with over 350,000 customers, serving popultion of round The verge dily consumption within the city of Lison ws round 170,000 m 3 /dy in Lison distriution network hs totl length of over km of pipes nd out 73,000 service connections, which re supplied y 14 reservoirs, ten pumping sttions nd five chlorintion sttions. Fig. 1 shows the Lison distriution network which hs five ltimetric supply zones, s well s threedimensionl representtion of the city elevtion nd its correspondence with the ltimetric zones of the EPAL distriution network. Fig. 1. () EPAL distriution network; () Tridimensionl view of Lison elevtion. EPAL network opertions nd mintennce re supported y full set of informtion systems, which includes the SCADA system, mintennce informtion system, GIS, illing customer system nd mthemticl model. The compny hs Commnd Centre which opertes 24 hours dy, 365 dys per yer, comprising oth Opertion nd Mintennce res. Aiming t the development of excellent stndrds in mngement indictors s regrds its principl ctivities, EPAL hs implemented qulity control systems, prticulrly s regrds environmentl nd socil responsiilities, ensuring tht network interventions, such s urst repirs, mins flushing nd reservoir clening, mongst others, re performed in ccordnce with set of well estlished procedures, including hygiene nd sfety prctices. 2. Distriution network segmenttion nd monitoring In recent yers, EPAL hs successfully implemented network monitoring project (WONE) imed t reducing wter losses. Incresing efficiency nd reducing wter losses is economic nd environmentl good prctice, with EPAL hving estlished itself s compny with the ility to nticipte nd resolve prolems ssocited with wter losses, which hs een chieved through the successful implementtion of the WONE Non-Revenue Wter (NRW) reduction project. The sis of this project hs een the progressive implementtion of more thn 150 District Metered Ares (DMAs), long with ssocited flow nd pressure monitoring equipment nd telemetry systems, undertken in prllel with the renewls nd rehilittion progrm. Through this process of network

3 N. Dis et l. / Procedi Engineering 70 ( 2014 ) segmenttion nd incresed monitoring nd nlysis, fr greter understnding of performnce nd systems dynmics hs een otined. The process of network segmenttion into DMAs with telemetry systems, set to record dt every 15 minutes, hs llowed the rpid intervention in cse of pressure or demnd nomlies. Note tht when n nomly occurs in pressure, such s when pressure t the criticl (highest) point within the DMA is less thn 5 m, telemetry equipment reports n lrm nd sends updted pressure nd flow dt. In June 2010, this project reched conclusion with 151 DMAs implemented, covering round 97% of clients nd 87% of network length. 3. Hydrulic modelling Although, for mny yers, there hve een severl genertions of mthemticl models, it ws only in 2008 tht EPAL developed internlly complete ll-pipe model of its distriution network, which ws sed on EPANET 2.0. Evolution, since eginning of this project through to the integrtion nd prcticl ppliction in 2009, shows tht EPAL hs recognized modelling s n nlyticl tool with strtegic importnce. Through prcticl pplictions of these models grdul ut progressive devition etween the modelling results nd rel monitoring dt hs een noted, eing explined the incresingly out of dte dt nd the models themselves, which were sed on 2007 scenrios. This led to generl updte of the models in 2012 given the significnt differences etween these two relities in reltion to: Existence of 152 DMAs in the distriution network, compred to 53 extnt in 2007; Reduced wter losses in the distriution network of 19.4 M m 3 /yer in 2007, equivlent to 17.2 % of the volume entered in Lison, to 11.6 M m 3 /yer (10.0 %) in 2011; Pipe renewls round 120 km etween 2007 nd 2011, which corresponds to pproximtely 8.4 % of the distriution network (pproximtely 2.1 %/yer); Implementtion of monitoring progrm for lrge volume users in Lison - in 2011 were monitorized out 750 users compred to 15 users monitored in To develop these models two distinct stges were considered, which correspond to: Stge 1 extended period clirtion for 24 hours (96 timesteps) pplied to ech ltimetric supply zone nd for mximum nd verge dily demnd; Stge 2 definition of representtive dys of typicl chrcteristics nd profiles for the distriution network. To updte the hydrulic models, it ws necessry to review nd vlidte physicl dt from GIS (mins, vlves, elevtion pumps, reservoirs, etc.), to define the height of every node within the network nd to ssocite demnd of ll clients to the models nodes, especilly in reltion to lrge volume users with telemetry (for which specific demnd ptterns were defined), sttus nd vlve timing, mongst others. Next, to the clirtion of ech ltimetric supply zone model for two specific dys ws undertken from 2011 (mximum nd verge dys), so tht the models results greed resonly with the oserved rel ehvior, in terms of levels nd flow rtes from tnks s well s pressure nd flow t the elevtion pumps, DMA metering points nd lrge volume users. Given the uncertinties s regrds ccurcy, pressure nd flow mesurements from EPAL s distriution network were djusted ccording to the criteri recommended y the WRC (referred in Coelho et l. (2006)), to clirte ech model. Therefore, in terms of pressure ll simulted vlues equled the rel mesurements with tolernce of 2 m of pressure, wheres the modelled flow equled the mesured flow with 5% tolernce. The second stge ws to estimte nd define the typicl ehvior of the distriution network on weekdys, Sturdys nd Sundys, s well s mximum nd verge demnd, so tht models re not just discrete representtion of the two historicl dys of dt used. In summry, t present, the models represent ll of EPAL distriution network through dynmic nlysis of the flow with 15 minutes time ptterns, which re chrcterized y the following physicl nd non-physicl components:

4 558 N. Dis et l. / Procedi Engineering 70 ( 2014 ) ,067 nodes nd 20 tnks; 37,337 mins sections, with over thn 1,450 km of length nd dimeters etween 20 nd 1500 mm; 51 elevtion pumps with respective chrcteristics curves Flow-Hed; 6,970 vlves, 30 of which re pressure reducing vlves; 73,734 demnd points with ssocited pttern; 954 elevtion nd demnd ptterns; 2,400 simple controls nd 1,026 rule-sed controls. 4. Integrtion of modelling nd monitoring 4.1. Overview The compny strtegy to comine network monitoring with mthemtic modelling hs een imed t improving cpcity in resolving suspected leks in the distriution network s well s undertking dignostic investigtions of network performnce whilst supporting plnning, mins sizing nd opertionl interventions. The first cse study demonstrtes the enefit of modelling optimiztion integrted with rel pressure nd flow dt to prove the existence of suspected lek. The second cse study revels the gret potentil for wter utilities which re fced with emergency situtions, where modelling cn e support tool for rpidly optimizing opertionl ctions nd procedures to mitigte nd mnge the potentil impct on service with rel network vlidtion from monitoring dt during nd fter implementtion of the optiml solution First cse study Lek loction with modelling nd monitoring An optimiztion methodology hs een pplied to support lek loction sed on hydrulic modelling. The ojective is to find prole lek loctions with the highest ccurcy possile, long with quntifiction of wter losses. This methodology is sed on otining pressure profiles t three loctions round suspected lek loction, llowing correltion nd optimiztion of the hydrulic model with the rel dt otined from pressure loggers. This cse study ws developed to ddress n outstnding issue identified during step-test in DMA, nmely DMA1060 Vle de Alcântr. A lek hd een identified ut not locted or repired due to lck of ccessile points for pplying coustic correltors on the suspect min. To otin further proof of existence of the lek s well s indictions s to its loction, two dditionl pressure loggers were instlled t strtegic points to supplement the existing pressure nd flow monitoring point ssocited with the djcent wstewter tretment plnt (lrge volume user with permnent telemetry), s shown t Fig. 2. This llowed the use of rel dt s se reference for clirtion of simplified nd djusted mthemtic model for the su-re under nlysis. The ojective of pplying the optimiztion tool consisted of testing multiple possile loctions for the lek, in this cse 45 nodes within the model, s well s vrying potentil emitter coefficient of the lek orifice over simultion period of six dys. In ddition, nlysis ws undertken on roughness coefficient ltertion long the cst iron min, which crosses min venue nd which ws the suspected loction of the undetected lek. Results otined from the vrious simultions were systemticlly compred with the rel pressure dt from the loggers, with the lowest error scenrios representing the ctul relity of the network in the re with the highest ccurcy. As result of mthemtic optimiztion nlysis, the suspected lek ws ctully locted on the cross-connection min with resonle error of ccurcy indeed ccurcy ws within the rdius of the excvtion required to ccess the min, given the depth t which it ws uried t the suspected point. It is importnt to note tht the gretest error ssocited with this methodology is essentilly the unknown rel roughness of the cst iron DN50 min, which cretes the need to mke ssumptions of vrious possile roughness vlues. The Fig. 2 shows the comprison etween the simulted nd rel pressure profiles long the suspected cst iron min, in one of the most prole scenrios for the lek loction.

5 N. Dis et l. / Procedi Engineering 70 ( 2014 ) Pressure & Flow (Wstewter Tretment Plnt) 41.0 Pressure t Node 2 Pressão no Nó Lg. Ponte Nov Prole Lek Loction Pressure (Node 2) Pressure (Node 1) Pressão (m c..) Pressure (m) :00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 Hour Hor Pressões Simulds Simultion Pressões Reis Telemetr Fig. 2. () Loggers loction round the suspected lek; () Comprison etween the simulted nd rel pressure profiles t Node Second cse study Opertionl optimiztion in emergency situtions First event Description nd opertionl mesures to reduce pressure impct The event tht triggered this cse study occurred on Mrch 9 th, 2010 when there ws lndslide on the 10 m tll slope djcent to the min, which forced the need to suspend one of the trunk mins for the lrgest ltimetric supply zone in Lison, referred to s the Chels-Olis min. Considering the proximity of the min to the lndslide, less thn 1 m nd the type of mins section, nmely DN600 ductile iron pipe without self-nchored joints, the mintennce tem decided to suspend the section immeditely nd indefinitely. The risk of keeping the min in opertion ws considered high with vrious hzrds identified, nmely immedite flood the surrounding re, third prty dmge nd elevted risk to humn life. Bsed on empiric experience, it ws known tht closing this min would cuse serious supply prolems in the centrl nd estern res of the supply zone. The known lterntives re through smller dimeter distriution mins, unle to supply the necessry volume in order to ensure the norml pressure, estimted increse of m 3 /dy with 700 m 3 /h t pek hour, with these estimted vlues eing sed on the model for weekdy with verge demnd. Before the suspension of the trunk min, the empiric nlysis sed on experience, 13 DMA vlves were opened to crete lterntive supply lines. However, through the hydrulic model nlysis, it ws found tht there might e etter solution to supply the re, so five dditionl DMA vlves were opened. At the pek consumption hour during the dy following the suspension of the min, there were six DMA pressure lrms (Fig. 3 noted s the grey res), hving mximum pressure vrition of 12 m hed. Despite efforts to mitigte the negtive effects of this suspension to clients, there ws decrese in pressure, s noted in Figure 3 on Mrch 10 th, which shows the comprison etween the rel telemetry efore nd fter the suspension. Consequently, there ws need to optimize network mngement, sed on the hydrulic model, in order to mximize the trnsport cpcity in the severl DN300 mins. The optiml theoreticl solution ws then determined nd implemented in phsed mnner to ensure network stility nd determine the rel impliction of ech step dopted ginst tht predicted y the model. After three dys the optiml solution ws implemented in the distriution network, hving improved pressures y round 4m nd low pressure lrms for just two DMAs. Note tht throughout these few dys there were operted 68 vlves to ensure the trnsport optimiztions for the most criticl res of the distriution network, s presented in Fig. 3.

6 560 N. Dis et l. / Procedi Engineering 70 ( 2014 ) Fig. 3. () First event: DMAs with pressure lrms (gry res) nd closed min pipe (ornge) () Pressure dt evolution with the optimiztion of trnsport supply fter the suspension Second event Burst t DN1000 min simultneously The second event of this cse study occurred six dys fter the first event (Mrch 15 th, 2010), on the min pipe referred to s the Cmpo Grnde-Poml trunk min, which serves to trnsport wter to the centre of this supply zone, with n estimted dily trnsport volume of 37,360 m 3 /dy with 2,150 m 3 /h t pek hour. Due to lrge urst tht thretened trffic on min rod in the city of Lison, the mintennce tem ws forced to suspend of this reinforced concrete DN1000 pipe, simultneously with the limittions imposed y the previous event. Agin, using the hydrulic model, the need to operte vlves ws study to ensure the est supply scenrio efore strting the suspension of the min pipe. At pek hour of the next dy were recorded 21 DMA pressure lrms (Fig. 4), with mximum pressure vrition of 20 m hed (Fig. 4), leving in some cses the distriution network with only 9 m of pressure. Fig. 4. () Second event: DMAs with pressure lrms (gry res) nd closed min pipes (ornge) () Pressure dt evolution with the optimiztion of trnsport supply fter oth suspensions.

7 N. Dis et l. / Procedi Engineering 70 ( 2014 ) Due to the nture of the urst (t the joint etween pipe sections), this min ws redy for opertion fter 30 hours of repir interventions from the outside of the min. However, two dys lter, second urst occurred, in this cse on curve section, forcing new suspension for repir. Knowing tht this suspension would cuse supply prolems similr to the previous event nd tht, in this cse, the repir suspension would hve n extended durtion of up to 96 hours, given the requirement to demolish the concrete lock to support the curved section, exterior repir nd reuilding the concrete lock gin, the mintennce tem ws forced to djust the repir procedure. Hence, it ws considered repiring the pipe section from the interior, y instlling type "AMEX" joint. Although this repir is fster, normlly tking round 14 hours to complete, the second vlves wy from the suspension vlves re required to e closed to ensure stff sfety within the min. 5. Tools to simplify the models usge To increse the cpcity to crete different scenrios for the hydrulic model nd simplify use of models within the compny, EPAL hs creted n Excel ppliction with Visul Bsic progrmming sed on simple nd userfriendly interfce to process the necessry chnges nd crete new input file for EPANET, s mentioned in Rossmn (2000). This se tool lso llows the user to develop lterntive scenrios of utomtic opertion, llowing the modifiction of operting dys (weekdys, Sturdys or Sundys) or demnd volumes, opening or closing of DMAs, chnging mins dimeters nd mteril, ltering vlve sttus, prepring dischrge plns nd incresed consumption due to new customers. These new cpilities imed t simplifying the use of models y technicins from different res of EPAL, without hving to mke chnges in the EPANET grphic user interfce. Also, with the im of mking more dptive modeling tool it ws creted the possiility for the user to choose, in the sme Excel file, preferences within the model for one ltimetric supply zone (Fig. 5), or integrted model for the five supply zones (Fig. 5), tht llow series of scenrios covering the whole distriution network. This is extremely importnt in lrge-scle interventions or emergencies, involving severl ltimetric supply zones nd is lso essentil to optimize energy consumption due to pumps elevtion for the entire distriution network, ccording to network demnds nd minimum nd mximum pressures t criticl points, thus contriuting to improving the efficiency nd effectiveness of the compny. Fig. 5. () Hydrulic models for ech ltimetric supply zone; () Integrted hydrulic model for the distriution network.

8 562 N. Dis et l. / Procedi Engineering 70 ( 2014 ) Also, to simplify scenrio nlysis nd comprison, EPAL hs creted nother Excel file, with EPANET Progrmmer's Toolkit progrmming, to run ech scenrio nd provide comprtive grphs nd tles for extended period simultions to list of selected nodes or links (or to ll nodes nd links) nd selected prmeters such s pressure, hed or demnd in nodes, flow or velocity in links. 6. Conclusions Nowdys, opertionl interventions within wter distriution utilities cnnot e sustined sed only on intngile fctors, nmely the intuition of their technicl stff or empiricl knowledge tht they hold. Improved service nd qulity levels tht these compnies re expected to deliver y their stkeholders re incresingly demnding so tht there is no second chnce to tke corrective ctions. Thus, the existence of decision support tools re essentil to optimize either ction plns, or in response to emergency situtions. During mintennce interventions in the wter distriution network, the mthemticl model highlights s one of the essentil tools for promoting improvements in service qulity, which lthough they my pper to e irrelevnt t first, ut hve, in prctice, significnt impct on client service. In the first cse study, it ws demonstrted tht prcticl integrtion of monitoring with hydrulic modelling otined evidence of lek nd n indiction of its most likely loction. With this proof, the mintennce tem hs creted the necessry ccess points to the pipe to pply coustic correltion. In the second cse study, the hydrulic model llowed pressure increse of out 4 m t the criticl point, which improved the supply to nerly two floors of uilding, which in turn led to drstic reduction in the numer of complints nd cler improvement in service qulity. However, the use of the model lone, when ny mjor event occurs is not sufficient to chieve the required results. It is necessry to undertke dily nlysis using continuous network monitoring, experience of technicl stff nd the inputs of clients through complints or wrnings of poor qulity supply. This continued nlysis llowed the optimiztion of service levels within three dys, through vlve opertion in order to increse the trnsport cpcity through lterntive mins, s well s understnding nd lerning, s regrds the mximum chievle limits for ech sector of the network. The introduction of mthemticl model within compny hs een slow nd grdul process tht hs to gin crediility mong technicins. When this sttus hs een chieved, the level of trust nd confidence in terms of decision mking, reches stndrds tht llow chnges nd improvements within the usul modus operndi. A greter level of trust nd confidence promotes etter plnning, regrdless of the level of intervention urgency, llowing efficiency nd effectiveness gins in the intervention ctions, which originte optimized service levels. As prcticl outcome, modelling ecomes tool for decision support tht reduces risk, increses the udcity, innovtion nd enling high consequence interventions, with greter level of confidence. Within the wter sector, ny intervention cn hve direct impct on everydy life of end users, so decision support tools which improve engineering knowledge re key tool to ssist with chieving improved efficiency levels tht re consistent with stkeholder expecttions. Whilst the se tools creted over recent yers re proving to e useful, EPAL, s ntionl reference wter utility, hs mde commitment to e prepred for the future, pplying methodologies nd nlyticl tools to support forecsting nd optimizing the dily mngement of wter supply systems. In ddition, wter utilities such s EPAL, will expect to increse their service efficiency nd effectiveness, whilst reducing their cron footprint. To chieve this gol, EPAL is interested in lerning out other innovtive projects supported y reserch nd development institutes which my e useful in pplying, developing nd improving our se tools towrds resolving potentil future scenrios. References Coelho, S. T., Loureiro, D., Alegre, H.,2006. Modelção e Análise de Sistems de Astecimento de Águ. Instituto Reguldor de Águs e Resíduos (IRAR) nd Lortório Ncionl de Engenhri Civil (LNEC), Lison, Portugl. Rossmn, L. A., EPANET Users Mnul. Drinking Wter Reserch Division, U. S. Environmentl Protection Agency, Cincinnti, U.S.A..