Presentation on theme: "Second IEC-CIGRE UHV Symposium, January 2009, New Delhi"— Presentation transcript:
1 Second IEC-CIGRE UHV Symposium, 29-30 January 2009, New Delhi 3-2Insulation Coordination for UHV AC Systems based on Surge Arrester Application (CIGRE C4.306)Eiichi ZaimaTokyo Electric PowerClaus NeumannRWE TSO StromJanuary 29, 2009Eiichi ZaimaConvenor, CIGRE WG C4.306Second IEC-CIGRE UHV Symposium, January 2009, New Delhi
2 IntroductionDifferent countries in the world, such as China, India and Japan, are planning and realizing UHV AC systems with the highest voltage of 1100kV and 1200kV.The research activities for UHV transmission within previous CIGRE SC33 has provided a good basis on the basic design for them.In the recent practice of UHV system, insulation coordination throughout substation and transmission line are generally based on metal oxide surge arresters and gas insulated switchgears (GIS, MTS).My presentation will cover the recent practice on insulation coordination for UHV AC systems from system aspects, the approved CDV (28/195/CDV) and the future work of CIGRE WG C4.306 (Insulation coordination for UHV AC systems)
3 Recent Practice of Insulation Coordination for UHV AC Transmission System
4 UHV Insulation Coordination Concept Insulation coordination throughout substation and transmission lineReduction of insulation levels to a reasonable level by sophisticated technologies.Practical application of high performancemetal oxide surge arresterReliable circuit breaker withclosing and/or opening resistorRational Insulation SpecificationSwitching OvervoltageInsulation Design Level(Transmission Line)LIWV(Substation)SIWV(Substation)
5 Overvoltages specific to UHV System (1) [TOV]Load rejection at a heavily loaded long line of UHV system produces TOV whose amplitude is p.u..[Slow-front overvoltage]Closing, opening, and ground fault overvoltages are of particular importance for UHV systems because they are the predominant factor of transmission tower size.[Fast-front overvoltage]Lightning overvoltages within UHV substation are greatly suppressed because they are the predominant factor of substation equipment size.[Very fast transient overvoltage (VFTO)]Disconnector switching overvoltages in UHV GIS are likely to exceed the lightning overvoltage if no measures are taken to control them.
6 Overvoltages specific to UHV System (2) Precise digital analysesExample of switching overvoltage calculation by EMTP and its measuring results in Japan’s 1100 kV projectExcellent agreementAccurate result of analyses
7 Switching Overvoltage Level and Suppression Measures Surge arresters and closing resistor have been basically used to suppress switching overvoltage on transmission line below switching overvoltage insulation design level.Open resistors have been adopted in Italy and Japan.
8 Application of High Performance Surge Arresters and LIWV High performance surge arrester can be applied in order to determine rational LIWV.
9 Standard Withstand Voltage for UHV Substation Equipment
10 LIWV and SIWV for UHV Substation Equipment Approved CDV(28/195/CDV) for amendment for IECNotes(4) This value is only applicable to the phase to earth insulation of single phase equipment not expose to air.(5) Presently in the IEC edition 6.2/ , Um=1200 kV is a standard value but in a proposed CDV submitted nowadays for vote the status is only under consideration. In the final version of this amendment, the final status of Um=1200 kV will be the one finally adopted in the revision or confirmation of IEC standard under the responsibility of TC 8.
11 Procedure of Insulation Coordination Flowchart for insulation coordination in IECInsulation coordinationSafety factorStandardization
12 Example of Selection of Insulation Level for UHV Equipment and Transmission Line
13 Japan’s 1100 kV Project (1)Switching overvoltage design level of transmission lineMeasures for overvoltage reductionSize reduction for towerSwitching Overvoltages are effectively reduced to pu by the application of closing/opening resistor (700) and high performance surge arrester at substation.Tower Height:143m 110mSwitching Overvoltage:2pu pu
14 Japan’s 1100 kV Project (2)LIWV: 1950 kV for transformer and 2250 kV for GIS(kV)LayoutofSurgeArresterTransformer195019501950195019501950LIWVGIS290029002900270025502250LIWVCost102 %105 %109 %103 %103 %100 %Economically Most Favorable Layouts of Surge Arresters
15 Japan’s 1100 kV Project (3)Lightning overvoltage at severe and normal substation conditionOvervoltage distributionI, II, III: severe circuit conditionIV: normal circuit conditionTransformerGISSevere condition1896 kV2208 kVNormal condition1850 kV2047 kV
16 Maximum switching overvoltage Japan’s 1100 kV Project (4)SIWV for substation equipmentFrom the system requirements,TransformerGISMaximum switching overvoltage1309 kV (1.46 p.u.)1400 kV (1.56 p.u.)Frequent overvoltage1250 kV (1.39 p.u.)SIWV1425 kV1550 kV ** Atmospheric correction of attitude 1000m (1.06) is considered.
17 Japan’s 1100 kV Project (5)Power Frequency Test Voltage for Substation EquipmentIt is a combination of “the short-duration section to confirm dielectric strength against temporary overvoltage” and “the long-duration section to confirm long-term dielectric strength against operating voltage”, based on the systematically accumulated data.1.5 p.u. 1h + 3 p.u. 5min p.u. 1h
18 China’s 1100 kV Project (1)Switching overvoltage design level of transmission lineSwitching Overvoltages are effectively reduced to 1.7pu by the application of closing resistor (600) and high performance surge arrester at substation.
19 Maximum lighting overvoltage China’s 1100 kV Project (2)LIWV with the consideration of safety factorLIWV Maximum lightning overvoltage Safety factor (1.15 for internal insulation)TransformerOther equipmentMaximum lighting overvoltage1796 kV2040 kVSafety factor1.15LIWV2250 kV2400 kV
20 (Residual voltage of 2kA) China’s 1100 kV Project (3)SIWV with the consideration of SPILSIWV SPIL (V2kA) Safety factor (1.15)TransformerOther equipmentSPIL(Residual voltage of 2kA)1460 kVSafety factor1.15SIWV1800 kV
22 CIGRE New WG C (1)Title of WG: “Insulation coordination for UHV AC systems”Recent practice of UHV insulation coordinationCollaboration with A3.22 and B3.22CDV(28/195/CDV) for amendment forStudy items1. Recent practice on insulation coordination for UHV systemInsulation coordination throughout substation and transmission lineReduction of insulation levels by application of high performance surge arresters and other overvoltagesuppression measuresContinued
23 CIGRE New WG C4. 306 (2) Study items 2. Overvoltage in UHV range (especially focused on peculiarity to UHV AC system)Determination of stresses (TOV, switching overvoltage,lightning overvoltage and VFTO) by simulation toolsand verification by measuring resultsTOV due to load rejection and ground faultSwitching overvoltages caused by closing and openingwith ground fault overvoltageLightning overvoltage caused by back-flashover anddirect lightning, VFTO stress in GIS due to disconnectorswitching (ref to CIGRE brochure "Monograph on GISVery Fast Transients 1989)Continued
24 CIGRE New WG C4. 306 (3) Study items 3. Review on insulation coordination of air gaps in the UHVrangePhase-to-phase insulation4. Selection of insulation levelsCoordination withstand voltages and safety factors forequipmentSelection of insulation levels for equipment andtransmission linesProposal of recommendation for application guide IEC (1996) by the end of 2010
25 CIGRE New WG C4. 306 (4) Membership National Committee Member Name Company / UniversityJapanEiichiZaimaTokyo Electric Power CompanyConvenorJapanTakayukiKobayashiTokyo Electric Power CompanySecretaryJapanJunTakamiTokyo Electric Power CompanyAsistant SecretaryBrazilPaulo CesarFernandezFURNAS Centrals ElectricascMCanadaDavidPeeloDF Peelo & Associates Ltd.RMCanadaQueBui-VanHydro Quebec TranEnergiecMChinaZehongLiuState Grid Corporation of Chinato be invitedFranceAlainSabotEDFRMFranceFrancoisGallonAreva T&Dto be invitedGermanyEdelhardKynastSiemensRMIndiaAshokPalPowergridRMItalyStefanoMalgarottiCESIRMJapanTokioYamagiwaJapan AE Power SystemRMKoreaEungboShimKorea Electric Power CompanyRMRussiaAndreyLokhaninElectrotechnical Research Instituteto be invitedSouth AfricaAsiffAmodESKOMto be invitedSwitzerlandUrsKrusiABB SwitzerlandRMSwitzerlandBernhardRichterABB SwitzerlandcM, A3.17 ConvenorThe United StatesAlbert J. F.KeriAmerican Electric PowerRMJapanHirokiItoMitsubishi ElectricRM, A3.22 ConvenorJapanTakeshiYokotaToshiba CorporationRM, B3.22 ConvenorRM=regular Member, cM=corresponding Member
27 ConclusionSophisticated insulation coordination is necessary for UHV system and should be technical-economically optimized throughout the UHV transmission line and substation.Reasonable insulation levels have been specified on the effective reduction of lightning and switching overvoltages by the application of high performance surge arresters and other measures, such as closing and/or opening resistors..A new CIGRE WG C “Insulation coordination for UHV AC system” will review and discuss the recent practice of UHV insulation coordination based on the approved CDV (28/195/CDV) and will investigate the safety factor. Finally, the WG will propose the recommendation for “Application Guide”.