U radu se daje tehnička analiza jednog incidenta koji se dogodio 21. ožujka 2007. godine u 00:50 sati u noći i doveo do dvosatnog potpunog raspada elektroenergetskog sustava na otoku Rodosu. Analiza događanja temelji se na registriranim operativnim podacima kao i nalazima na terenu. Izvršena je tehnička analiza smetnji kako bi se utvrdili vjerojatni uzroci i čimbenici koji su pridonijeli pojavi smetnji. S obzirom da se radi o izoliranom sustavu koji je osobito je osjetljiv na poremećaje, ispitane su uloge zaštite sustava kao i kolebanja proizvodnje vjetroelektrana tijekom incidenta. Izvučeni su zaključci od praktičnog značenja i dane su preporuke korektivnih mjera koje valja provesti kako bi se u budućnosti spriječile takve smetnje.A technical review of an incident on March 21, 2007 that began at 00:50 a.m. and led to a two-hour blackout of the island of Rhodes electric power system is presented with the complete sequence, including all the relevant registered operational data as well as the on-site field findings. A technical analysis of the disturbance was performed to determine the probable causes and factors that contributed to the duration of the disturbance. Since the system is an isolated one, it is particularly vulnerable to perturbations. The roles of system protection and wind power generation during the incident are examined. Conclusions of practical importance are drawn, including recommendations for corrective measures to be implemented for preventing disturbances of this kind from reoccurring in the future

Ch. Tsichlakis

E. J. Thalassinakis

M. T. Papazoglou

N. D. Hatziargyriou

Th. M. Papazoglou

Hrčak - Portal of scientific journals of Croatia

608U radu se daje tehniËka analiza jednog incidenta koji se dogodio 21. oæujka 2007. godine u 00:50 sati u noÊi i doveo do dvosatnog potpunog raspada elektroenergetskog sustava na otoku Rodosu. Analiza dogaanja temelji se na registriranim operativnim podacima kao i nalazima na terenu. Izvrπena je tehniËka analiza smetnji kako bi se utvrdili vjerojatni uzroci i Ëimbenici koji su pridonijeli pojavi smetnji. S obzirom da se radi o izoliranom sustavu koji je osobito je osjetljiv na poremeÊaje, ispitane su uloge zaπtite sustava kao i kolebanja proizvodnje vjetroelektrana tijekom incidenta. IzvuËeni su zakljuËci od praktiËnog znaËenja i dane su preporuke korektivnih mjera koje valja provesti kako bi se u buduÊnosti sprijeËile takve smetnje.A technical review of an incident on March 21, 2007 that began at 00:50 a.m. and led to a two-hour blackout of the island of Rhodes electric power system is presented with the complete sequence, including all the relevant registered operational data as well as the on-site ﬁ eld ﬁ n-dings. A technical analysis of the disturbance was performed to determine the probable causes and factors that contributed to the duration of the disturbance. Since the system is an isolated one, it is particularly vulnerable to perturbations. The roles of system protection and wind power generation during the incident are examined. Conclusions of practical importance are drawn, including recommendations for corrective measures to be implemented for preventing distur-bances of this kind from reoccurring in the future.KljuËne rijeËi: izolirani elektroenergetski sustav, nestanak strujeKey words: blackout, isolated electric power systemDIJAGNOSTI»KI PREGLED RASPADA ELEKTROENERGETSKOG SUSTAVA NA OTOKU RODOSUDIAGNOSTIC REVIEW OF A BLACKOUT IN RHODESProf Papazoglou, Th. M., PhD, Prof Papazoglou, M. T., PhD, The Technological Education Institute of Crete, P.P. Box 1939, Iraklio, Crete, Greece Prof Thalassinakis, E. J., PhD, Prof Tsichlakis, Ch., PhD, Prof Hatziargyriou, N. D., PhD, The Greek Power Public Corporation, The testing Research and Standard Center ∑ DEH S.A., 32 Halkokondili Street, 10432 Athens, Grece Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D., DijagnostiËki..., Energija, god. 56(2007), br. 5., str. 608-617Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D., Diagnostic..., Energija, vol. 56(2007), No. 5, pp. 608-617ENERGIJA 5-2007 05.indd   608 12/6/07   1:51:30 PMENERGIJA 5-2007 05.indd   609 12/6/07   1:51:31 PM610Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D., DijagnostiËki..., Energija, god. 56(2007), br. 5., str. 608-617Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D.,  Diagnostic..., Energija, vol. 56(2007), No. 5, pp. 608-6171 UVODIzolirani otoËni elektroenergetski sustavi zanimljivi su s tehniËkog stajaliπta jer pokazuju neke izrazi-te znaËajke. Ako je u takvim sustavima prisutan i visok stupanj proizvodnje vjetroelektrana, javlja se u odreenim okolnostima veÊa osjetljivost na pogonske poremeÊaje.Elektroenergetski sustav grËkog otoka Rodosa izolirani je sustav s ukupno 234 MW instaliranog kapaciteta termoelektrana (5 dizelskih, 2 parne i 4 plinske turbine) te 15 MW instalirane snage u vjetroelektranama. Meutim, zbog nekih teh-niËkih problema i karakteristika termoelektrana, stvarna snaga termoelektrana iznosi tek pribliæno 192 MW. Godine 2006. proizvodnja u satu vrπnog optereÊenja iznosila je 192,6 MWh. To znaËi da sustav nije uvijek imao na raspolaganju rezervnu snagu.U ovom se Ëlanku istraæuje incident poremeÊaja sustava 21. oæujka 2007. godine koji je zapoËeo u 00:50 sati u noÊi i doveo do dvosatnog raspada elektroenergetskog sustava na otoku Rodosu.U vrijeme neposredno prije incidenta u pogonu su bili dva parna bloka (ATM 1 i ATM 2), svaki optereÊen s 10 MW (rotirajuÊa rezerva svakog agregata 2 MW), dva dizelska bloka (D1 i D3): s optereÊenjem 6 MW (rotirajuÊa rezerva 5 MW), ostala proizvodnja s 12 MW (rotirajuÊa rezerva 5 MW) te 12 MW vjetroelektrana. Vremenski uvjeti bili su loπi i jamaËno su odigrali odreenu ulogu na poËetku incidenta. Na slici 1 dana je jednopol-na shema sustava.Smetnje u sustavu zapoËele su asimetriËnim trofa-znim kratkim spojem bez zemljospoja. Taj je kvar uspjeπno uklonjen. Meutim, zbog nestabilnosti uzrokovane zaπtitnim mehanizmima sustav se nije oporavio veÊ je postupno gubio proizvodnju i izazi-vao znaËajnu redukciju optereÊenja πto je, nakon 2 minute i 45 sekundi od uklanjanja prvog kvara, konaËno dovelo do potpunog raspada elektroener-getskog sustava.1 INTRODUCTIONIsolated island power systems are of interest from the technical point of view because they exhibit no-table characteristics. For example, when there is a high penetration of wind generation, there is greater vulnerability to operation perturbations under cer-tain conditions.The electric power system of the Greek island of Rhodes is an isolated system with 234 MW in-stalled capacity of thermal plants (5 diesel, 2 steam and 4 gas turbines) plus 15 MW wind generation. However, due to some technical problems and the characteristics of the thermal generating plant, the actual thermal generation capacity is only about 192 MW. In the year 2006, the mean average hour-ly generation peaked at 192,6 MWh. This means that the system did not have appreciable reserve power at all times.This article examines the system disturbance inci-dent of March 21, 2007 that began at 00:50 a.m. and led to a two-hour blackout of the Rhodes Island Electrical Power System.At the time just before the incident, the system was operating with 2 steam units (ATM 1, and ATM 2) with 10 MW production each (a spinning reserve of 2 MW each) and 2 diesel units (D1, and D3): one producing 6 MW (with a 5 MW spinning reserve) and the other generating 12 MW (with a 5 MW spinning reserve). At the same time, wind genera-tion was 12 MW. A one-line diagram of the system is shown in Figure 1. The weather conditions were severe and played a deﬁ nite role at the start of the incident.The system disturbance began with an asymmetri-cal three-phase fault, not involving ground. This fault was successfully cleared. However, due to in-stabilities triggered by the protective mechanisms, the system never really recovered, gradually losing generation and causing signiﬁ cant load shedding, which ﬁ nally led to a complete blackout lasting 2 minutes and 45 seconds after the initial fault had been cleared.ENERGIJA 5-2007 05.indd   610 12/6/07   1:51:32 PM611 Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D., DijagnostiËki..., Energija, god. 56(2007), br. 5., str. 608-617Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D.,  Diagnostic..., Energija, vol. 56(2007), No. 5, pp. 608-617Kvar se dogodio na trafostanici Rhodini na dis-tribucijskom vodu napajanom putem prekidaËa P-320 od 15 kV sabirnice, kako je prikazano na slici 1. Nakon gubljenja struje iz voda aktivirana je zaπtita i otpuπteni su prekidaËi P-320, P-255 i P-225. Zbog kvara je izgorio drveni stup distri-bucijskog voda te se kasnije morao zamijeniti. Vrijeme je bilo vrlo loπe u trenutku kvara, pri Ëemu je jak vjetar rasprπivao kapljice morske vode po izolatorima vodova, πto je intenziviralo povrπinsko praænjenje. Naknadnom analizom pronaen je srednji fazni vodiË (u vodoravnom rasporedu od 3 faza) prekinut na jednom drvenom stupu. Isto se dogodilo s drugim stupom istog voda gdje su, osim prekinutog srednjeg vodiËa, takoer bili razbijeni porculanski izolatori, najvjerojatnije kao posljedica struje zemljospoja. Taj je poËetni kvar konaËno uklonjen oko 13 sekundi nakon πto se dogodio. Meutim, 19 sekundi nakon uklanjanja kvara ispao je parni blok #1 a potom, 2 minute i 45 sekundi nakon uklanjanja kvara, i parni blok #2, πto je rezultiralo raspadom elektroenergetskog sustava.The fault occurred at the Rhodini substation on the distribution line fed through the breaker P-320 from the 15 kV bus, as shown in Figure 1. Following the fault, protection was activated and tripped the breakers P-320, P-255 and P-225. As a result of the fault, a wooden pole of the distri-bution line burned and had to be replaced later. The weather was severe at the time of the fault, with strong wind spraying sea water droplets over the line insulators, thereby increasing the likelihood of a ﬂ ashover. Post-mortem examination found the jumper wire for the middle phase conductor (in a horizontal arrangement of the 3 phases) cut at another wooden pole of the same distribution line. The same thing also happened to another pole of the same line where, in addition to a broken middle jumper wire, its porcelain insulators were also bro-ken. This would most likely imply that these were the results of the fault current. This initial fault was ﬁ nally cleared at about 13 sec after it happened. However, 19 sec after the fault clearance, Steam Unit #1 was lost, and 2 min and 45 sec after the fault clearance Steam Unit #2 was lost, resulting in the blackout.Slika 1 Jednopolna shema sustava na poËetku smetnjeFigure 1One-line diagram of the system at the start of the faultENERGIJA 5-2007 05.indd   611 12/6/07   1:51:32 PM612Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D., DijagnostiËki..., Energija, god. 56(2007), br. 5., str. 608-617Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D.,  Diagnostic..., Energija, vol. 56(2007), No. 5, pp. 608-6172 ANALIZA INCIDENTAKako sustavu SCADA u kontrolnom centru nedo-staju neke vaæne funkcije bilo je moguÊe tek samo biljeæenje pogonskih podataka u realnom vremenu, dok se u mnogim sluËajevima dogaaju znaËajna zakaπnjenja u biljeæenju podataka. Iz ispitivanja zabiljeæenih dogaaja i podataka moguÊe je za-kljuËiti kako je smetnja zapoËela asimetriËnim trofaznim kratkim spojem bez zemljospoja. Ovaj zakljuËak temelji se na vremenskim krivuljama izmjeniËne struje zabiljeæenih digitalnim relejima prekidaËa P-225 i P-255 (slika 2), koji su poka-zivali nepostojanje struje zemljospoja. Moglo se takoer zamijetiti da impendancije kvara variraju s vremenom, upuÊujuÊi na elektriËno iskrenje kao uzrok. Oscilogrami 1 i 2 (slike 3 i 4) prikazuju napone na sabirnicama 66 kV na trafostanici Rho-dini, odnosno struje na prekidaËu 66 kV P-110 onako kako su se i razvijali. Naknadni vremenski oscilogrami 3 i 4 (slike 5 i 6) tu oscilaciju (fre-kvencije 100 Hz) jasnije prikazuju. Oscilacija se odræava do kraja (kao πto je razvidno iz oscilograma 5 (slika 7). To moæe znaËiti i da je automatskim regulatorima napona (AVR) potrebno podeπavanje.Iz oscilograma napona moguÊe je izraËunati veliËi-nu napona kao funkciju vremena, i to od nastanka kvara do potpunog pada napona, kako je prikazano na slici 8.Tijekom smetnje zabiljeæene su promjene frekven-cije πirokog raspona. Relevantni podaci prikazani su na slici 9 na kojoj je vidljiva minimalna fre-kvencija od 47,7 Hz (2 s nakon poËetka smetnje) i maksimalna frekvencija od 54 Hz (16 s nakon poËetka smetnje).2 INCIDENT ANALYSISAt the outset, one should note that the SCADA at the Control Center leaves important functionalities to be desired. As a result, real-time registration of operation is only partially possible, while in many cases signiﬁ cant time delays occur in data regis-tration. From examination of the registered events and data, one is able to see the following. The fault began as an asymmetrical three-phase fault, not in-volving the ground. This was evident from the time alternating current curves registered by the digital relays of the P-225 and P-255 (Figure 2) breakers, which showed zero earth current. It could also be observed that the fault impedances varied randomly with time, suggesting that the electric-arcing of varying spans was the cause. Oscillograms 1 and 2 (Figures 3 and 4) show the voltages at the 66 kV buses at Rhodini and the currents at the 66 kV breaker P-110, respectively. These oscillograms show oscillation developing as time progresses. Subsequent time Oscillograms 3 and 4 (Figures 5 and 6) show this (100 Hz fre-quency) oscillation more clearly. This oscillation is sustained to the end (as seen in Oscillogram 5 (Figure 7). This could indicate that the automatic voltage regulators (AVR) need adjustments.From the voltage oscillogram, one can calculate the voltage magnitude as a function of time, from the occurrence of the fault up to the voltage collapse, as shown in Figure 8.In the course of the disturbance, wide frequency swings were registered. The respective data are shown in Figure 9. In this ﬁ gure, one can see the minimum frequency of 47,7 Hz (2 s after the start of the disturbance), and the maximum frequency of 54 Hz (16 s after the start of the disturbance).ENERGIJA 5-2007 05.indd   612 12/6/07   1:51:33 PM613 Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D., DijagnostiËki..., Energija, god. 56(2007), br. 5., str. 608-617Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D.,  Diagnostic..., Energija, vol. 56(2007), No. 5, pp. 608-617Tijekom smetnje tri su se dodatna Ëimbenika poka-zala kljuËnima. Podeπenja podnaponske zaπtite za park vjetroelektrana kao i za pojedinaËne vjetroge-neratore imala su za posljedicu ispade generatora i gubitak proizvodnje iz vjetroelektrana (24 % uku-pne proizvodnje). Podeπenja zaπtite poduzbudnih limitera dizelskih elektrana imala su za posljedicu njihov ispad. Ispadanje 40 MW optereÊenja, zbog rada automatske podfrekvencijske zaπtite, rezulti-ralo je u preostaloj snazi od 10 MW napajanoj iz parnog bloka #2 u zadnjim trenucima neposredno prije potpunog ispada.In the course of events, three additional fac-tors were shown to be crucial. The under-voltage protection settings for the wind park and for the individual wind generators resulted in the loss of wind generation (24 % of the total generation). The under-excitation limiters protection settings of the diesel units resulted in the loss of those units. The shedding of 40 MW of load, due to the operation of the automatic under-frequency protection, resulted in a remaining load of 10 MW which was fed from Steam Unit #2 in the ﬁ nal moments just before the collapse.Slika 2Vremenske krivulje izmjeniËnih struja faza a, b, c i uzemljenja na prekidaËu P-255Figure 2Time curves of the alternating currents of Phases a, b, c and ground at breaker P-2552.7951.3980-1.398-2.795-1750 -1500 -1250 -1000 -750 -500 -250 0 250 5002.7951.3980-1.398-2.7950.6160.3080-0.308-0.616Slika 3Oscilogram 1 ∑ Naponi na sabirnici 66 kV na trafostanici Rhodini (poËetak gubljenja struje iz voda) Figure 3Oscillogram 1 ∑ Voltages at the 66 kV bus at Rhodini (the fault begins)Zygos 1 fase AZygos 1 fase BZygos 1 fase CENERGIJA 5-2007 05.indd   613 12/6/07   1:51:33 PM614Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D., DijagnostiËki..., Energija, god. 56(2007), br. 5., str. 608-617Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D.,  Diagnostic..., Energija, vol. 56(2007), No. 5, pp. 608-617Slika 4Oscilogram 2 ∑ Struje zabiljeæene na prekidaËu 66 kV P-110 na trafostanici RhodiniFigure 4 Oscillogram 2 ∑ Currents registered at 66 kV Breaker P-110 at RhodiniZygos 1 fase AZygos 1 fase BZygos 1 fase CSlika 5Oscilogram 3 ∑ Naponi na sabirnici 66 kV na trafostanici Rhodini Figure 5 Oscillogram 3 ∑ Voltages at 66 kV bus at RhodiniZygos 1 fase AZygos 1 fase BZygos 1 fase CSlika 6 Oscilogram 4 ∑ Naponi na sabirnici 66 kV na trafostanici RhodiniFigure 6 Oscillogram 4 ∑ Voltages at 66 kV bus at RhodiniZygos 1 fase AZygos 1 fase BZygos 1 fase CENERGIJA 5-2007 05.indd   614 12/6/07   1:51:33 PM615 Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D., DijagnostiËki..., Energija, god. 56(2007), br. 5., str. 608-617Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D.,  Diagnostic..., Energija, vol. 56(2007), No. 5, pp. 608-617Slika 7 Oscilogram 5 ∑ Napon na sabirnici 66 kV na trafostanici Rhodini (nestanak struje vidljiv na kraju)Figure 7 Oscillogram 5 ∑ Voltage at 66 kV bus at Rhodini (blackout seen at the end)Zygos 1 fase AZygos 1 fase BZygos 1 fase CSlika 8Varijacija napona na sabirnici 66 kV (u %) tijekom smetnjeFigure 866 kV bus voltage variation (in %) during the disturbance120100806040200Vrijeme / Time (s)Napon / Voltage (%)0 30 60 90 120 150 180Slika 9Trend varijacije frekvencije zabiljeæen tijekom smetnjeFigure 9Frequency variation trend registered during the disturbance54.553.552.551.550.549.548.547.5Vrijeme / Time (s)Frekvencija / Frequency0 2 4 6 8 10 12 14 16 18 20 22 24 26 28(Hz)ENERGIJA 5-2007 05.indd   615 12/6/07   1:51:34 PM616Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D., DijagnostiËki..., Energija, god. 56(2007), br. 5., str. 608-617Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D.,  Diagnostic..., Energija, vol. 56(2007), No. 5, pp. 608-6173 ZAKLJU»CIElektroenergetski sustav otoka Rodosa, kao jedan izoliran sustav, osjetljiv je na smetnje. Distribucij-ski sustav srednjenaponskih nadzemnih vodova u blizini obale takoer je osjetljiv na uËinke morske soli koja negativno utjeËe na pouzdanost izolacije.Osjetljivost proizvodnje vjetroelektrana na koleba-nja u naponu mreæe kao i ukupna zaπtita sustava odigrale su kljuËnu ulogu u razvijanju poremeÊaja koji je doveo do raspada elektroenergetskog sustava.TrenutaËno se razmatra nadogradnja prijenosnog sustava na otoku Rodosu sa sadaπnjih 66 kV na 150 kV πto bi se trebalo realizirati u naredne dvije do tri godine. Osim izgradnje prijenosne mreæe, potrebno je nadograditi i sustav SCADA te sustave zaπtite.3 CONCLUSIONSAs an isolated system, the Rhodes Island system is vulnerable to disturbances. The MV overhead line distribution system in the vicinity of the coast is also vulnerable to the effects of sea salts that ad-versely affect the reliability of insulation.The sensitivity of wind generation to voltage swings as well as the overall system protection played a critical role in the development of the perturbation which led to the blackout.In view of the fact that the transmission system on Rhodes Island is currently being considered for an upgrade from the present 66 kV to 150 kV, sched-uled for the next two-to-three years, it is important that the SCADA system is upgraded as well. The protection scheme should also be upgraded. ENERGIJA 5-2007 05.indd   616 12/6/07   1:51:34 PM617 Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D., DijagnostiËki..., Energija, god. 56(2007), br. 5., str. 608-617Papazoglou, Th. M., Papazoglou, M. T., Thalassinakis, E. J., Tsichlakis, Ch., Hatziargyriou, N. D.,  Diagnostic..., Energija, vol. 56(2007), No. 5, pp. 608-617Uredniπtvo primilo rukopis:2007-07-25PrihvaÊeno:2007-09-27LITERATURA / REFERENCES[1] Internal Incident-Report DEH, Blackout of the Rhodes EPS on 21.03.2007 (Interno izvjeπÊe o inci-dentu, Kolaps elektroenergetskog sustava Rodosa 21.03.2007)[2] Marconato, R., Electric Power Systems, Volume 2 (Second Edition), CEI ∑ Italian Electrotechnical Committee, Milano, 2004Manuscript received on:2007-07-25Accepted on:2007-09-27ENERGIJA 5-2007 05.indd   617 12/6/07   1:51:34 PM

DIAGNOSTIC REVIEW OF A BLACKOUT IN RHODES

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