Effect of Time-Variability Weather Conditions on the Reliability of Distribution Systems

Transcription

1 7th WSEAS Iteratoal Coferece o Electrc Power Systems, Hgh Voltages, Electrc Maches, Vece, Italy, November -3, Effect of Tme-Varablty Weather Codtos o the Relablty of Dstrbuto Systems M. R. ZARE, R. HOOSHMAND, S. ESHTEHARDIHA, M. BAYATI POODEH Islamc Azad Uversty, Males Brach; Electrcal Egeerg the Uversty of Isfaha IRAN Abstract: -Relable evaluato of dstrbuto systems s of hgh mportace the mateace ad expaso of these systems. A tme-sequetal smulato techque s preseted ths paper whch the effects of weather codtos ad mateace methods the assessmet of relable cost of tegrated dstrbuto systems are provded. Tme-Varyg Weght Factors (TVWF) are defed to vestgate the effect of weather codtos ad preset mateace methods o Falure rates (FR). I fact, the average Falure Rate (FR) s combed wth TVWF to provde tme-varyg repar tmes (TVRTs) for each compoet. Smlarly, the average Repar Tme (RT) s also combed wth TVWF to produce Tme- Varyg-Repar Tme (TVRT). A expermetal dstrbuto system showed that TVFR has more effects o the terrupto costs of the sestve costumers. It has also sgfcat effects o the dces of all costumers. So, t s ecessary to cosder TVRT evaluatg the relablty of the etwork cost. Key-Words: - Dstrbuto systems, etwork reforcemet, relablty cost/worth Itroducto The subscrber's terrupto costs ad reforcemet relablty costs of the etwork are useful dces for the etwork desgers whle makg optmum desgs ad admstratve decsos [] [3]. The relablty of these dces has great effects o the fal decsos made by the etwork desgers. The dex relablty depeds upo the techques, compoet parameters, ad the models employed the aalyss. The techques employed for the relablty assessmet of the power systems are totally dvded to aalytc graphs [4]-[5], Mote Carlo [5] [8], ad a combato of smulato ad aalytcal methods [9]. The relable parameters are mostly cosdered to be costat the aalytcal techques. So, the Falure Rate ad Repar Rate (RR) parameters are costat. Tme To Falure (TTF) ad Tme To Repar (TTR) have expoetal dstrbutos. I actual power systems the restorato tme ca have other dstrbutos such as ormal or logormal. The FR s a fucto of the weather codtos ad evromet. I adverse weather codtos, the Falure Rate of a compoet mght be larger tha that the ormal weather codtos [0]. The repar tmes of the compoets are also affected by varable weather codtos as well as repar methods. Restorato tme durg a wter seaso s greater tha that cosdered for a ormal amout. The repar tme also depeds o whether t s daytme, ght, weekday or weeked. I a gve weather codto the average tme requred for restorato durg a weeked or wth some hours at ght ca be greater tha the usual amout durg the weekdays or daytme. The equvalet two-state model ad the four-state weather model are employed [0] ad [], respectvely. Costat falure rate ad repar tme are cosdered these models. Bllto ad L [] employed the Mote Carlo samplg techque to corporate varable weather codtos a composte form. A uform dstrbuto for weather codto samplg based o occurrece probablty ad weather codtos was employed. The weather codtos are dvded to ormal ad adverse all states. The probabltes of ormal ad adverse codtos are employed to corporate the effect of weather. The data aalyss of weather codtos ad repar methods are ot cosdered [0] ad []. The tme-varyg ature ad ucertaty of the system parameters ca ot be easly cosdered whle employg aalytcal methods. The result of data aalyss ad system radom behavor by the applcato of chroologcal smulato wth the assumpto of tme-varable load ad terrupto cost models s preseted [8]. Vag ad Bllto dd ot cosder the tme-varyg FR ad TR [8]. Istead of the applcato of the probabltes of adverse or ormal weather codtos, the ssues of Tme-Varyg Falure Rate (TVFR) ad Tme- Varyg Restorato Tme (TVRT) are defed ths artcle to specfy the weather codto effects ad varable repar methods o the relablty of parameters of a compoet. The chroologcal

2 7th WSEAS Iteratoal Coferece o Electrc Power Systems, Hgh Voltages, Electrc Maches, Vece, Italy, November -3, smulato techques for the corporato of the results of data aalyss ad system radom behavor are used the evaluato of relablty. The effects of the load pots of the relable cost/worth dces of the system o TVFR ad TVRT are preseted Expected Eergy Not Suppled (EENS) ad the Expected terrupto COST (ECOST) for a test dstrbuto system. The Relablty Worth of Network Reforcemet (RWNR) was studed to show the mportace of employg TVRT. Tme-varyg models. Dagram Model Tme-varyg compoet models are two-state model for the evaluato of the relablty of a dstrbuto system for a compoet.the FR ad RR are cosdered costat ths model. The tmevaryg two-state model ths study s depcted Fg.. The falure rate at t tme s calculated by the followg equato: λ (t) w(t). λ (t) () Where w(t) s tme-varyg weght dex, ad FR λ() s the FR for ormal weather codtos..3. TVRT Model Tme-varyg repar tme: the weather codtos ad repar methods both affect the system repar tme. The effect of weather codtos are produced by the weather weght factors whch are calculated by the past repar expermets of the power compay for dfferet weather codtos. The weather weght factors wth weather data aalyss scale are corporated to form a tme-varyg weather factor. W w (t) of the preset repar methods ca be produced by a daly TVRT weght factor. W d (d) ad also a hourly TVRT weght factor W h (t) based o swtchg expermets ad repar. The repar tme (t) ca be obtaed by equato () r whch s the repar tme for ormal weather codtos. Fg.. Dagram depctg tme-varyg two-state system The FR ad RR are fucto of tme ad oe year s dvded to 8760 dscrete hours. The FR of each compoet for each hour s assumed to be costat ad the repar tmes have a logormal dstrbuto. Other dstrbutos ca also be selected for the descrpto of repar tmes... Weather Codto The tme-varyg falure rate (FR) dvdes the evromet weather to three groups usg IEEE 346[3].. ormal. adverse 3. strog storm The falure rate s costat for a gve weather codto. I ths paper the tme-varyg falure rate s defed to represet the tme-varyg ature of falure rate. A TVFR or λ(t) ca be obtaed by usg average FR ormal weather codtos weghted by weather data aalyss scale as Fg.. Fg.. Tme-varyg weather codto weghg dagram Fg.3. Hourly TVRT weght factors The hourly TVRT weght factors used ths paper are depcted Fg.3. Fg.4. Weekly TVRT weght factors The Weekly weght factors are depcted Fg.4. The daly TVRT weght factor s. durg a weeked. r(t) w w (t) w (d) w (t) r d h () It should be oted that the am of ths paper s to

3 7th WSEAS Iteratoal Coferece o Electrc Power Systems, Hgh Voltages, Electrc Maches, Vece, Italy, November -3, obta a geeral method for cosderg the tmevaryg ature the relablty of cost/worth assessmet. The falure rate ad repar tmes are weghed durg wter ad summer. The weghted factors used a actual system are based o the system past repar expermet dfferet weather codtos. Attemptg to provde uversal tme varable models for each parameter to be applcable for each power etwork s ot realstc..4. Load Models ad Average Iterrupto Costs Load models ad Average Iterrupto Costs (AIC) for seve dfferet types of customers are calculated o the bass of ther Sector Customer Damage Fuctos (SCDF). I [4] the SCDF s depcted Fg. 5. Ns MWh EENS L V ( ) λ (4) yr I whch, r terrupto durato resultg from m elemet o m rego. 33KV 3 KV Lp3 Lp Lp4 Lp N/O Fg.6. The etwork uder study 4 THE CALCULATION OF DISTRIBUTION FACTORS IN SAMPLE NETWORK Fg.6 depcts the teded sample etwork whch umbers dcates the elemets of 0 ad 33-kv etworks ad the locatos of 0.4 ad 0 kv power stato specfy the load pots. Fg.5. Load models ad average terrupto costs Average models ad tme-varyg varables for costs ad load are expressed [8] that ca be used aalyss. 3. EENS AND ECOST PARAMETERS The ECOST s preseted as follows: Ns K.S ECOST L C λ ( ) (3) yr I whch, the umber of elemets affectg ECOST The umber of the regos wth probable terruptos studed ECOST calculato. N s The total umber of the elemets causg falures smulato perod. C terrupto cost per ut. L average load accordg to KVA Also, EENS dces preseted as follows: a) Specfcatos related to the sample etwork Two weather codtos: Average durato of ormal weather 680hr, λ 0.039F / yr Average durato of adverse weather 48hr, λ s 5.86F / yr Wth regard to equato (5) λ ca be calculated: s λ eq ( λ ) + ( λs ) (5) + s s+ I whch s the ormal codto hours ad s s the adverse codto hours. b) Trasmsso le codtos: Bus bars: BUS kv: λ b 0.00F / yr BUS 33kv: λ b 0.00F / yr Breakers: BUS kv: λ bc 0.006F / yr

4 7th WSEAS Iteratoal Coferece o Electrc Power Systems, Hgh Voltages, Electrc Maches, Vece, Italy, November -3, Trasformers: depcted the above dces Fg. 8. Loads: Tras. kv / 0.45kv : λ T 0.05F / yr Tras. 33kv /kv : λ T 0.05F / yr P 650KVA, P 400KVA P 3 400KVA, P 4 34KVA Les: L 6km, L km,l 3 3km, L 4 km L 5 6km,L 6 km,l 7 3km,L 8 km Wth regard to graph (5) ad cosderg C 0.5% ($/hr) for four tmes. For the calculato of ECOST of the total system, t s ecessary to specfy the effect of 8 elemets o each of the eght regos ad the ther resultg values are added together ad the EENS ad ECOST of the total system are obtaed. It s ecessary to study dfferet states to specfy the effects of weather codtos o the above dces. Fg.8. ECOST ad EENS CRT, CFR, TVRT states To better compare the obtaed results ad prove that the tme-varyg weather codto has greater effect o the above factors, the obtaed results are studed through Fg. 9. A. Sample etwork (case ) I ths state the value of λ ad r are cosdered to be costat ad the values of ECOST ad EENS are calculated for the whole system. Costat falure rate CFR ad costat repar tme CRR. B. Sample etwork (case ) I ths state r s costat CRR ad λ s the form of TVFR ad has a drect effect o the calculato of the above dces. As depcted Fg.7, the effect of weather codtos o the above dces s evdet. Fg. 9. ECOST ad EENS graphs case,, 3 As t was expected from the above graphs, we reached a cocluso, that by cludg weather codtos repar codtos there were more effects o the EENS ad ECOST dces ad by ths cluso the system approaches actual codtos ad leads to more accurate values to be cosdered the study. Now we troduce the RWNR dex system for the comparso of weather effect o ECOST whch s calculated as follows: RWNREcostB-EcostA (6) ad the resultat graphs are obtaed as Fg. 0. Fg.7. ECOST, EENS graphs CRT, CFR, TVFR states C. Sample etwork 3 (case 3) I ths case λ s cosdered costat. CFR ad r are a fucto of weather codtos TVRT. It s effect s Fg.0. EWNR graph TVFR ad TVRT states

5 7th WSEAS Iteratoal Coferece o Electrc Power Systems, Hgh Voltages, Electrc Maches, Vece, Italy, November -3, ASSESSMENT OF THE RELIABILITY OF DISTRIBUTION NETWORK Assessmet of dstrbuto system relablty s carred out by the related dces that IEEE stadard presets them. These dces are defed as load pot dces. 5. Load pot dex I the calculato of relablty, the requred parameters should be specfed for each load pot (0 0.4) KV as well as for each crcut elemet. These parameters are: A. Falure rate (λ): Falure average umber for each compoet a defte tme. The falure rate s usually expressed accordg to the umber of falures a year. B. Repar tme (r): The tme requred to replace or repar the faulty compoet ad start workg aga. Repar tme s usually expressed hours. C. Swtch tme (st): The legth of tme lastg for the faulty compoet to be dscoected from the etwork ad other compoets be electrfed case t s possble wth regard to the ew etwork arragemet. Swtchg tme s expressed hours. Other parameters to be preseted ths part s the accessblty to eergy or uavalablty (u). These parameters represet aual tme durato for a compoet to be dscoected from a etwork. Ths tme durato s calculated by multplyg (r) ad (λ) ad ts ut s hours/year. U λ r λss r s (7) λ r r Us s (8) λ λ s s λ λ (9) Radal dstrbuto system s modeled the form of seral system. Therefore, equatos related to seral system s also true for t. I ths system, the above parameters ca be obtaed from the followg equatos. 5. System dces A. System average terrupto durato dex (SAIDI) UN Total customer terrupto duratos SAIDI N Total umber of customers (0) N s the umber of the customers for N load pot ad U s the tme durato for ts ext. For the above sample system s as Fg.. Fg.. System average terrupto durato dex (SAIDI) B. System average terrupto frequecy dex (SAIFI) λn Total customers terruptos SAIFI N Total customers () N s the umber of the customers coected to N load pot ad λ s the falure rate. Ths dex shows that how may tmes each customer expereces terrupto o average durg the specfed tme as Fg. the above system. Fg.. System average terrupto falure dex (SAIFI) C. Customer average terrupto durato dex (CAIDI) UN Total customer terrupto tme duratos CAIDI λ Total customer terruptos N () I ths dex, the average terrupto tme for each customer for each terrupto s cosdered. Ths s vestgated the above system Fg. 3.

6 7th WSEAS Iteratoal Coferece o Electrc Power Systems, Hgh Voltages, Electrc Maches, Vece, Italy, November -3, as well as repar tme or etwork coecto shftg tme. Ths s because the calculato of relablty s ot vald ad we ca ever use them as parameters desg wthout havg access to statstcs based o facts. Fg.3. Customer average terrupto durato dex D. Average system avalablty dex (ASAI) UT UN ASAI NT Customer avalablty total hours durg study Total hours for all customers durg study (3) Ths dex shows the customer accessblty rate to electrcty the percetage of the hours coected relato to the tme durato total hours that leads to the results Fg.4. for the above system cosderg oe-year durato. Fg.4. Average system avalablty dex (ASAI) 6 CONCLUSION It s possble to calculate the relablty a dstrbuto system by obtag the ufed eergy ad relable dces through the method preseted the paper. The optmzato of the etwork ca be carred out by ths method. By studyg the effect of weather codtos ad ther effects o the falure ad repar promotg codtos as t was predcted before ad wth regard to the results obtaed we ca coclude that the TVRT codtos o ECOST ad EENS dces of the system are more effectve tha the TVFR state o the teded system whch results hgher dces of SAIDI ad CAIDI of the system. It s mportat to ote that the calculato of relablty, the accessblty to relable results based o actual data s possble whe the power dustry ca provde precse ad comprehesve statstc for the compoet ad elemet falures the etwork Refereces [] M. J. Sullva, T. Vardell, B. N. Suddeth, ad A. Voda, Iterrupto costs, customer satsfacto ad expectatos for servce relablty,, IEEE Paper 95 SM, 57-8 PWRS. [] J. G. Dalto III, D. L. Garrso, ad C. M. Fallo, Valuebased trasmsso plag,, IEEE Paper 95 SM, PWRS. [3] G. Neudorf et al., Cost beeft aalyss of power system relablty:two utlty case studes, IEEE Tras. Power Syst., vol. 0, pp , Aug [4] R. E. Brow, S. Gupta, R. D. Chrste, S. S. Vekata, ad R. Fletcher, Dstrbuto system relablty assessmet usg herarchcal Markov modelg, IEEE Tras. Power Delvery, vol., pp , Oct [5] R. Bllto ad P.Wag, Teachg dstrbuto system relablty evaluato usg Mote Carlo smulato, IEEE Tras. Power Syst., vol. 4, pp , May [6] P. Nofer, L. Pars, ad L. Salvader, Mote Carlo methods for power system relablty evaluato trasmsso ad geerato plag, Proc. Au. Relab. Mataab. Symp.,Washgto, DC, Paper 94, 975. [7] J. C. O. Mello, M. V. F. Perera, ad A. M. Lete da Slva, Evaluato of relablty worth composte systems based o pseudo_sequetal Mote Carlo smulato, IEEE Tras. Power Syst., vol. 9, pp , Aug [8] P. Wag ad R. Bllto, Tme sequetal dstrbuto system relablty worth aalyss cosderg tme-varyg load ad cost models, IEEE Tras. Power Delvery, vol. 4, pp , Jul 999. [9] M. V. F. Perera, M. E. P. Macera, G. C. Olvera, ad L. M. V. G. Pto, Combg aalytcal models ad Mote Carlo techques probablstc power system aalyss, IEEE Tras. Power Syst., vol. 7, pp.65 7, Feb. 99. [0] R. Bllto ad R. N. Alla, Relablty Evaluato of Power Systems. New York: Pleum, 984. [] K. A. Clemets, B. P. Lam, D. J. Lawrece, T. A. Mkolas, A. D. Reppe, R. J. Rglee, ad B. F.Wolleberg, Trasmsso system relablty methodsmathematcal models, computg methods ad results, Power Techologe Ic., Scheectady, NY, EPRI EL-56, Jul. 98. [] R. Bllto ad W. L, A ovel method for corporatg weather effects composte system adequacy evaluato, IEEE Tras. Power Syst., vol. 6, pp , 99. [3] Terms for Reportg ad Aalyzg Outages of Electrcal Trasmsso ad Dstrbuto Facltes ad Iterruptos to Customer Servce, IEEE Stad. 346, 973. [4] R. N. Alla, R. Bllto, L. Goel, I. Sarref, ad K. S. So, A relablty test system for educatoal purposes-basc dstrbuto system data ad results, IEEE Tras. Power Syst., vol. 6, pp , 99.