A HUGE STEP FOR THE CROATIAN P POWER SYSTEM AND THE ...

ELECTRA N°212 - Février 2004N°212 - Février 20041212

SummarySummary

This article describes the back-ground, realisation and applied techni-cal solutions of the new construction of400/110 kV Ernestinovo substation ineastern Croatia. Due to the fact that thissubstation, together with its intercon-necting lines, is one of the most impor-tant facilities for realisation of re-con-nection of the two currently existingUCTE synchronous zones, some basicinformation is given about that issue.

ForewordForeword

New construction of 400/110 kVErnestinovo substation as well as asso-ciated overhead lines, realised byHrvatska Elektroprivreda (HEP - Croat-ian National Electricity), with respect tothe Croatian power system and its neigh-bouring power systems, but also severalother European power systems has mul-tiple justification, but the major one –from UCTE1 system point of view – cre-ated preconditions to restore intercon-nections at 400 kV towards Bosnia &

Herzegovina and Serbia & Montenegro,which is crucial for the re-connection ofthe entire UCTE synchronous area.

The most recent technological solu-tions have been applied to the primaryequipment and systems as well as sec-ondary ones during reconstruction ofS/S 400/110/35kV Ernestinovo.

Substantial improvements havebeen made on the secondary equip-ment – such wide and complex solu-tions applied to the system of super-vision, control, protection, monitoringand metering are used among the mostadvanced State-of-the-art solution in aHEP power grid.

BackgroundBackground

Ernestinovo substation is situatedin the eastern part of Croatia, about15 km south of Osijek (centre of thearea of Slavonia). The original substa-tion was constructed with three con-necting 400 kV lines in the mid 1970’s.

The substation was constructed asthe main supply point for the easternpart of the Croatian power system (with

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A HUGE STEP FOR THE CROATIANA HUGE STEP FOR THE CROATIANPOWER SYSTEM ANDPOWER SYSTEM ANDTHE EUROPEAN INTERCONNECTEDTHE EUROPEAN INTERCONNECTEDGRID RECONSTRUCTIONGRID RECONSTRUCTIONOF THE ERNESTINOVO 400/110 KVOF THE ERNESTINOVO 400/110 KVSUBSTATION*SUBSTATION*IIVICA TOLJAN (HEP, Z(HEP, ZAGREBAGREB))

DDAMJAN MEDIMOREC, ZELJKO KOSCAK (HEP-T(HEP-TRANSMISSIONRANSMISSION, Z, ZAGREBAGREB))

SSIME MILISA, MISO JURKOVIC, IVAN DAIDZIC,HHRVOJE KORASIC (KONCAR-KET, Z(KONCAR-KET, ZAGREB))

SSILVIO BRKIC (HEP-T(HEP-TRANSMISSIONRANSMISSION, Z, ZAGREBAGREB))

* For more details, you may contact:(from Koncar) [email protected]

(from HEP) [email protected]

1. UCTE stands for “Union forthe Co-ordination of Transmissionof Electricity” (the association of

transmission system operators forthe coordination of the electricity

interconnection in mainland Europe).

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No. 212 - February 2004 ELECTRA

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the peak load of that area ranging 350-400 MW in 1990’s) with the aim to enabletransit of electricity through 400 kV lines(in the amount approximately double inrespect of the electricity supplied to thelocal consumption area). The ordinarydirection of power transit, was from theeast (of former Yugoslavia) to the west.Ernestinovo substation was a part of thenorthern route in the so called 400 kV“Nikola Tesla” ring that connected allparts of former Yugoslav power system.

Ernestinovo substation suffereddestruction of 85 % of its equipmentand area, together with one third of alltransmission lines (OHL) of high volt-age (110, 220 and 400 kV) levels inwider surroundings of the substation.

Therefore a series of provisionalarrangements were made in order toensure the minimum supply of therespective consumption in the easternpart of Croatia – and they lasted morethan anybody expected, until recently.

The fact that Ernestinovo substa-tion with surrounding overhead lineswas disabled represents one of themain reasons the UCTE system hasbeen operating in two separate syn-chronous zones, since the end of 1991 :

1.1. the main part of the UCTE (or socalled the 1st synchronous zone), hasbeen in synchronous operation withthe CENTREL system (the CzechRepublic, Hungary, Poland, the Slo-vak Republic - that become fullmembers in 2001) since 1995, hasbeen in synchronous operation withthree (Maghreb) countries of NorthAfrica since 1997, and finally hasbeen in trial synchronous operationwith the “Burshtyn Island” (the west-ernmost part of Ukraine) since 2002.2.2. the 2nd synchronous zone (Mace-donia, Greece, Serbia&Montenegroand part of Bosnia & Herzegovina,with Bulgaria and Romania thatbecame full members in 2003) hasbeen in synchronous operation withAlbania.

New beginningNew beginning

This outlined separation along suchwide “interface” from Adriatic toUkrainian Carpathian mountainsmakes the re-connection of the UCTEsynchronous zones (including alreadyrealised extension to Bulgaria, Roma-nia and the “Burshtyn island”) one ofthe most challenging and complexprocesses comparable to significantextensions of synchronous area in thepast.

The substation, positioned almostin the centre of above mentionedinterface between two presently exist-ing UCTE synchronous zones providesan additional link close to the largestproduction facilities and consump-tions areas near the interface. This isnot only of symbolical or geographi-cal relevance, but contributes toestablishing preconditions for smoothrealisation of the re-connection pro-cess without endangering system reli-ability or stability (both globally andlocally). Following increase of publicsensitivity for such issues during lastyear, this is now more important thanever before.

The largest part of the Croatianinvestment program for (re)construc-tion of its transmission grid includedfacilities needed for synchronous re-connection of the UCTE grid, main ofthem being Ernestinovo 400/110 kVand Îerjavinec 400/220/110 kV sub-station with connecting 400 kV over-head lines for Ernestinovo substation(Ernestinovo-Îerjavinec, Ernestinovo-Ugljevik, Ernestinovo-Mladost).The so called Ernestinovo Programincluded new construction of 170 kmof overhead lines (110, 220 and400 kV) with installation of 150 kmOPGW and for connection of the newÎerjavinec substation four new over-head lines (total length of 28 km)were foreseen.


The implementation of this invest-ment program was postponed severaltimes until 2001 because of a lack offunds. After unsuccessful negotiationswith different international financialinstitutions, including those followingan international call for financing andapplication for financial support fromTEN (Trans European Networks) fundsthrough Greek government, HEP asinvestor had to secure funds througha domestic commercial loan.

Previously accomplished preparatoryworks on the respective sites (e.g. clear-ance of substation area and overheadline’s routes with access roadways) aswell as on the main project design andtender documentation were prepared.

After the International CompetitiveBidding Procedure finished in January2002, the project was awarded in March2002 to the Consortium of five KONCARfactories and Dalekovod Inc., led byKONCAR – Power Plant and ElectricTraction Engineering Inc., Zagreb ofCroatia, which was evaluated as the bestoffer.

The contract has required projectimplementation on the, so called,“turn key” basis, which means, designfor construction, supply and deliv-ery of equipment, inclusive civilworks, installation, testing and com-missioning, “as built” documentationas well as warranty period for24 months.

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FFIGIG.1: T.1: TWO SYNCHRONOUS AREAS OFWO SYNCHRONOUS AREAS OF UCTE UCTE SYSTEMSYSTEM..

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in advance.

Description of the projectDescription of the project ((Reconstruction of 400/110kV Ernestinovo Substation-Croatia)

rest of three OHL are connectedtowards the S/S Îerjavinec (nearZagreb), Ugljevik (Bosnia and Herze-govina) and Mladost/Sremska Mitrovica(Serbia and Montenegro).

The configuration ensures higherflexibility and reliability as usually appliedfor such kind of switchgear for nationaland international power exchange.

110kV switchgear110kV switchgear

110 kV switchgear is placed in thenorthern part of the substation. It com-prises 3 sectioned busbar systems thatare extended over 26 bays out of whichone is equipped with shunt-reactor110 Mvar and 9 (nine) are spares.

The configuration ensures, due tosectioning, higher flexibility and relia-bility of the system.


Indoor 35 kV switchgear is metal-clad air insulated type with withdraw-able vacuum circuit breakers driven bymotor-spring operating mechanism.

Switchgear configuration with two-sided power supply and single-sec-tioned busbars enables separate oper-ation of the 35 kV lines and 35/0,4 kV,2x1000 kVA auxiliary transformersachieved by sectioning.

Secondary equipementand system

Secondary system is a distributedmicro processing system with co-ordi-nated functions of supervision, control,protection and metering by usage ofnumeric protection devices, bay controlunit (BCU), station control unit (SCU)and optical infrastructure. The advan-tage of this type of solution is the pos-sibility of achieving more functions usingthe same optical infrastructure.


The substation covers the area ofapprox 320 x 260m.

S/S Ernestinovo is constructed as a400/110 kV substation, outdoor AIS typewith two, and after a future extension,three 300 MVA main power auto-trans-formers. Main power auto-transformersare with OLTC to enable the regulationof secondary voltage under load.

400 kV switchgear is placed in thesouthern part of the substation. Itcomprises 14 bays, each 21 m wide.The busbar system consists of twomain busbars that are extendedthrough all the switchgear bays andone auxiliary busbar system that isextended through 12 bays, only (forOHL bays, while transformer bays arenot connected to auxiliary busbars).

Two 400 kV OHL bays are equippedfor connection of planned double cir-cuit line towards Hungary, although theOHL would be built later on, while the


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FFIGIG. 2: C. 2: CROATIAN GRID WITH ITSROATIAN GRID WITH ITS 400 400 ANDAND 220 220 KKV V FACILITIES AND RELEVANTFACILITIES AND RELEVANT

FACILITIES OF NEIGHBOURING GRIDSFACILITIES OF NEIGHBOURING GRIDS ((HIGHLIGHTEDHIGHLIGHTED--MAJORMAJOR CCROATIAN TRANSMISSIONROATIAN TRANSMISSION

SUBSTATIONS FOR RESUBSTATIONS FOR RE--CONNECTIONCONNECTION))


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The main functions of the systemare:– signalisation of positions andalarms– automatic voltage regulation – registration of disturbance mag-nitude– chronological registration of events– control, interlocking and syn-chronisation

– protection– metering – self-control and failure signalling

The system enables supervision andcontrol (SCADA) functions at thefollowing levels:– bays (from relay houses)– remote control centre (RCC)-Osi-jek

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FFIGIG. 4: 400/110. 4: 400/110KKV, 300MVA MV, 300MVA MAINAIN AAUTOTRANSFORMERUTOTRANSFORMER..

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FFIGIG. 3: 420. 3: 420KKV CV CIRCUIT BREAKERSIRCUIT BREAKERS & D& DISCONNECTORSISCONNECTORS..


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– National Dispatch Centre (NDC)-Zagreb– station/switchgear (from the con-trol room).Data transmission between bay

control units and station control unitsis serial and unbalanced over fibre opticcables. The supervision and control ofthe entire substation is provided atplant level by means of LSA VIEW(SCADA) installed on the operator sta-tions, each bay can be supervised atboth levels.

The central part of the system at theplant level consists of two redundant6MB5515 station control units, whichcollect information from the bay level(400 & 110kV) and common parts of thestation (35kV and auxiliaries) and per-form station control and telecontroldata distribution.

One of them is defined as the pro-cess control unit and other as the hot-standby unit. Both HMI operator work-stations are connected to bothredundant station control units and itis defined via software whether opera-tor places are run parallel or they arestandby.

The telecontrol connection is per-formed via an optical switch overdevice.

The redundancy at bay level isachieved by local control in case of fail-ure of the supervision and control sys-tem. Local control is performed on theback-up panel by means of push buttons.This control is performed in non-inter-locked mode. Correct functioning of abay level unit is not affected by failureson other bays or at plant level.

400 and 110 kV OHL, 400/110 kVtransformers, 110 kV shunt-reactor and400 and 110 kV busbars have been pro-tected through the use of devices inmicroprocessor technology with opti-cal-electrical communication.

Protection of 400 kV OHL-s areredundant using two numerical relayswith separate measuring, tripping andDC supply circuits. Furthermore, com-municational paths were split for com-

munication with protection on the otherend of the line. Basic protection of thereactor was supplemented by adetached over-current protection withautonomous tripping. 400 and 110 kVbusbars protection has a built-in circuitbreaker failure protection.

35kV feeders are protected usingfeeder terminals with integrated pro-tection and control functions.

For the fault analysis, appropriatecommunication between protectionunits and the protection department inOsijek has been established. Commu-nication encompasses conveying ofinformation such as: supervision, adjust-ment of protection parameters, mag-nitudes of disturbances as well as loca-tion of the failure, recording protectionsignals, etc.

Metering in the substation includesservice and billing measurements.

The service measurements areshown:

– locally in the relay houses – at station level – at higher level centres (RCC &NDC) via IEC 60870-5-101 protocolBilling measuring is an autonomous

system independent of the LSA(SCADA) system, and is performed bymeters and registration devices.

TelecommunicationTelecommunicationsystemssystems

The development of the telecom-munication and information system ofHEP depends greatly on transmissionsystems. They were installed untilrecently as analogue systems of diversecapacity. However, as new technologiesdeveloped, these have become obso-lete. Therefore, new digital systemshave been introduced into HEPtelecommunications system.

S/S 400/110kV Ernestinovo, as animportant substation in internationalenergy exchange, is connected to the


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existing telecommunications systemand meets high standards. Such animportant substation has requiredquality linking with higher-rankingRCC Osijek and other neighbouringsubstations with which the substationis linked energy-wise. Substation sys-tem of telecommunications consistsof:

– Power-line carrier links over HVlines (PLC)– RR links– Optical links – Internal communication andsystemsTo comply with all switching require-

ments towards HEP connection net-work, Hrvatski Telekom (HT) - publictelecommunication network and inter-nal communications in substation itself,HEP digital automatic telephoneswitchboard (ISPBX) has been installedin the substation.

Auxiliary power supply(AC/DC systems)(AC/DC systems)

Substation power supply 0,4 kV,50Hz consists of:– two 35/0, 4 kV, 1000kV auxiliarytransformers connected to 35 kVswitchgear. 35kV switchgear isconnected to the distribution grid(S/S-s 110/35 kV, Osijek 1 & 2) bytwo 35 kV underground cables.– two 0,4kV, 250 kVA diesel-gen-erating sets. Each set covers thedemand of critical consumers. – 10/0,4 kV, 250kVA S/S tower out-door type via connection to 10 kVdistribution grid.

Substation power supply 220V &48V DC are distributed.

220 V DC power supply has beenrealised by usage of 16 DC Sys-

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FFIGIG. 5: SCADA S. 5: SCADA SYSTEMYSTEM – B– BLOCK DIAGRAMLOCK DIAGRAM..


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tems placed in a decentralized way intothe relay houses, control/main andMV/LV buildings. Each decentralizedsystem has, with respect to the AC sup-ply, a double connection. With respectto DC, the redundancy has beenachieved by connection to the neigh-bouring supply system.

Each DC System is integrated frommodular and redundant rectifiers, VRLAbatteries, selective DC distributionboards and microprocessor controlunit.

48 V DC power supplying fortelecommunication has been realisedby usage of 2 DC Systems in redundantoperation. Each DC System is inte-grated at the same principles as 220 Vsystems.

Major achievementsMajor achievements

NEW TECHNOLOGIESNEW TECHNOLOGIESDEVELOPED AND APPLIEDDEVELOPED AND APPLIED

– Composite insulators– Power transformer monitoring– New self-blast breaking systemas well as energy of arc extinction(thermal effect) to reduce energy ofoperating mechanism on 420 &123 kV CB– No capacitors on 420kV CB withtwo interrupting chambers– Distributed DC system with HFrectifiers and chargers– Intensive usage of optical infras-tructure

ENGINEERING ACTIVITIES:ENGINEERING ACTIVITIES:– Complete design for construction,selection of equipment, integrationof systems, parametering, installing,testing and commissioning, includ-ing system functioning warranty aswell as “as built” documentations.– Integration of technologies(HW+SW) made and delivered byseveral worldly recognised manu-factures within supervision and con-trol systems,

– Solution for optical infrastructure(due to distribution) for connectionof different technologies and man-ufacturers for supervision, control,protection, monitoring, telecom-munication, fire protection andother safety requirements as wellas audio-video monitoring/super-vision – Process data exchange withneighbouring countries and UCTE(IEC-TASE 2 protocol)

Such complex conditions haverequired a special approach to organi-sation of the project management.

Collaboration, assistance andengagement of supervision engineersand specialists of the Client (HEP –Transmission Ltd.) have been very use-ful and substantial to the Consortium.Such a collaboration has been crucial infulfilling of the main objective – con-struction of the substation just as it wascontracted, i.e. high quality withinrequired delivery time of 18 months.

The same or very similar solutions areimplemented in new 400/220/110/20 kVS/S Zerjavinec project by the same con-tractor. The substation has been almostcompleted.

Benefits for the regionaland European grids

New construction of Ernestinovosubstation as an important part ofHEP’s (re)construction programme ofthe Croatian transmission grid has beenpriority investment based on the tech-nical criteria aiming to restore nationaltransmission links between easternCroatia and the rest of the country aswell as international links that areimportant for power transfer betweenseveral countries. This particular invest-ment will ensure :

➤ ➤ At the national level:– establishing of original pre-warelectricity network situation, with

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abolishment of provisional networkarrangements and other alternativeemergency supply measures thatwere put in place after the destruc-tion of the previously existing facil-ities, but remained common causesfor interruptions of electricity sup-ply in eastern Croatia– meeting the standards for relia-bility and quality of electricity sup-ply– reducing of transmission systemlosses– reducing electricity generatingcosts due to enabling better plantdispatch– transports and transits of energyto and from other countries– contribution to establishment ofsound and solid infrastructure basisfor economic development of theeastern Croatia that suffered heavydamages or destruction of infras-tructure.

➤ ➤ At the broader (regional) level:– establishment of electricity infras-tructure necessary for synchronousre-connection of UCTE 2nd syn-chronous zone to the main UCTE grid– increasing security and reliabilityof supply in a wider part of the elec-tricity grid– enabling cross border transit andtrade among different countries – enabling easier meeting of grow-ing electricity consumption require-ments and therefore decreasingpressure for construction of newpower plants in the region– enabling competitive supply ofelectricity for the broader regionwith significant interconnection linescapacities

➤ ➤ Towards the full reconnection ofUCTE zones

At present construction and instal-lation works and testing have beencompleted - Ernestinovo substation iscommissioned. For its full operation acomplex programme will be executed

following commissioning of new 400 kVsubstation Îerjavinec (near Zagreb) inspring this year.

According to the current status ofinformation, other infrastructure pro-jects needed as a precondition for there-connection of the two presentlyexisting UCTE synchronous zones arescheduled to be completed by the mid-dle of this year (reconstruction pro-gramme of 400 kV overhead lines inBosnia & Herzegovina) or are alreadycompleted (grid reinforcement withnew Sandorfalva-Bekescsaba 400 kVoverhead line in Hungary). Then therealisation of large scale re-connectionitself is expected to commence follow-ing implementation of other necessarymeasures that are responsibility of des-ignated UCTE body (Executive Teamfor North-South Re-Synchronization)prepared under framework of the socalled Multilateral Re-synchronizationProgram. The last phase will compriseorganisation of a certain monitoringand analysis period after re-synchroni-sation in order to allow for permanentreliable operation conditions of theentire system.

Completion of this process willimpact operational conditions atregional and European (whole UCTE)level and provide for a functioning mar-ket base, influencing also the develop-ment of further electricity infrastructureprojects, particularly interconnectionsthat are important for a broader region,such as Ernestinovo – Pécs 400 kVoverhead line (between Croatia andHungary).

Then, Ernestinovo substation, nowin state-of-the-art technology for a newlifetime, will again be reliable node inthe transmission grid of the (broader)region, which will after extensionplanned for forthcoming years (400 kVdouble circuit overhead line Ernesti-novo – Pécs) connect electrical powersystems of four countries. ��

A HUGE STEP FOR THE CROATIAN P POWER SYSTEM AND THE ...

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