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1 Insulation Coordination for UHV AC Systems based on Surge Arrester Application (CIGRE C4.306) January 29, 2009 Eiichi Zaima Convenor, CIGRE WG C4.306.

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Presentation on theme: "1 Insulation Coordination for UHV AC Systems based on Surge Arrester Application (CIGRE C4.306) January 29, 2009 Eiichi Zaima Convenor, CIGRE WG C4.306."— Presentation transcript:

1 1 Insulation Coordination for UHV AC Systems based on Surge Arrester Application (CIGRE C4.306) January 29, 2009 Eiichi Zaima Convenor, CIGRE WG C Claus Neumann RWE TSO Strom Eiichi Zaima Tokyo Electric Power Second IEC-CIGRE UHV Symposium, January 2009, New Delhi

2 2 Introduction Different 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 3 Recent Practice of Insulation Coordination for UHV AC Transmission System

4 4 UHV Insulation Coordination Concept Practical application of high performance metal oxide surge arrester Reliable circuit breaker with closing and/or opening resistor LIWV (Substation) Rational Insulation Specification SIWV (Substation) Switching Overvoltage Insulation Design Level (Transmission Line) Insulation coordination throughout substation and transmission line Reduction of insulation levels to a reasonable level by sophisticated technologies.

5 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 6 Overvoltages specific to UHV System (2) Precise digital analyses Example of switching overvoltage calculation by EMTP and its measuring results in Japan’s 1100 kV project Excellent agreement Accurate result of analyses

7 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 8 Application of High Performance Surge Arresters and LIWV High performance surge arrester can be applied in order to determine rational LIWV.

9 9 Standard Withstand Voltage for UHV Substation Equipment

10 10 LIWV and SIWV for UHV Substation Equipment Approved CDV(28/195/CDV) for amendment for IEC Notes (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 11 Procedure of Insulation Coordination Flowchart for insulation coordination in IEC Insulation coordination Standardization Safety factor

12 12 Example of Selection of Insulation Level for UHV Equipment and Transmission Line

13 13 Japan’s 1100 kV Project (1) Switching overvoltage design level of transmission line Switching Overvoltages are effectively reduced to pu by the application of closing/opening resistor (700  ) and high performance surge arrester at substation. Tower Height: 143m  110m Switching Overvoltage: 2pu  pu Size reduction for towerMeasures for overvoltage reduction

14 14 LIWV: 1950 kV for transformer and 2250 kV for GIS Japan’s 1100 kV Project (2) (kV) Layout of Surge Arrester GIS LIWV Transformer Cost 102 %105 %109 %103 % 100 % LIWV Economically Most Favorable Layouts of Surge Arresters

15 15 Japan’s 1100 kV Project (3) Lightning overvoltage at severe and normal substation condition Overvoltage distribution TransformerGIS Severe condition 1896 kV2208 kV Normal condition 1850 kV2047 kV I, II, III: severe circuit condition IV: normal circuit condition

16 16 Japan’s 1100 kV Project (4) SIWV for substation equipment TransformerGIS Maximum switching overvoltage 1309 kV (1.46 p.u.)1400 kV (1.56 p.u.) Frequent overvoltage1250 kV (1.39 p.u.) * Atmospheric correction of attitude 1000m (1.06) is considered. From the system requirements, SIWV1425 kV1550 kV *

17 17 Japan’s 1100 kV Project (5) Power Frequency Test Voltage for Substation Equipment 1.5 p.u.  1h +  3 p.u.  5min p.u.  1h It 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.

18 18 China’s 1100 kV Project (1) Switching overvoltage design level of transmission line Switching Overvoltages are effectively reduced to 1.7pu by the application of closing resistor (600  ) and high performance surge arrester at substation.

19 19 LIWV with the consideration of safety factor China’s 1100 kV Project (2) LIWV  Maximum lightning overvoltage  Safety factor (1.15 for internal insulation) Transformer Other equipment Maximum lighting overvoltage 1796 kV2040 kV Safety factor1.15 LIWV2250 kV2400 kV

20 20 SIWV with the consideration of SPIL China’s 1100 kV Project (3) SIWV  SPIL (V 2kA )  Safety factor (1.15) Transformer Other equipment SPIL (Residual voltage of 2kA) 1460 kV Safety factor1.15 SIWV1800 kV

21 21 Future Plan by CIGRE C4.306

22 22 CIGRE New WG C (1) 1. Recent practice on insulation coordination for UHV system Insulation coordination throughout substation and transmission line Reduction of insulation levels by application of high performance surge arresters and other overvoltage suppression measures Study items Recent practice of UHV insulation coordination CDV(28/195/CDV) for amendment for Title of WG: “Insulation coordination for UHV AC systems” Continued Collaboration with A3.22 and B3.22

23 23 CIGRE New WG C (2) 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 tools and verification by measuring results TOV due to load rejection and ground fault Switching overvoltages caused by closing and opening with ground fault overvoltage Lightning overvoltage caused by back-flashover and direct lightning, VFTO stress in GIS due to disconnector switching (ref to CIGRE brochure "Monograph on GIS Very Fast Transients 1989) Study items Continued

24 24 CIGRE New WG C (3) 3. Review on insulation coordination of air gaps in the UHV range Phase-to-phase insulation 4. Selection of insulation levels Coordination withstand voltages and safety factors for equipment Selection of insulation levels for equipment and transmission lines Study items Proposal of recommendation for application guide IEC (1996) by the end of 2010

25 25 CIGRE New WG C (4) Membership RM=regular Member, cM=corresponding Member National CommitteeCompany / University JapanEiichiZaimaTokyo Electric Power CompanyConvenor JapanTakayukiKobayashiTokyo Electric Power CompanySecretary JapanJunTakamiTokyo Electric Power CompanyAsistant Secretary BrazilPaulo CesarFernandezFURNAS Centrals ElectricascM CanadaDavidPeeloDF Peelo & Associates Ltd.RM CanadaQueBui-VanHydro Quebec TranEnergiecM ChinaZehongLiuState Grid Corporation of Chinato be invited FranceAlainSabotEDFRM FranceFrancoisGallonAreva T&Dto be invited GermanyEdelhardKynastSiemensRM IndiaAshokPalPowergridRM ItalyStefanoMalgarottiCESIRM JapanTokioYamagiwaJapan AE Power SystemRM KoreaEungboShimKorea Electric Power CompanyRM RussiaAndreyLokhaninElectrotechnical Research Instituteto be invited South AfricaAsiffAmodESKOMto be invited SwitzerlandUrsKrusiABB SwitzerlandRM SwitzerlandBernhardRichterABB SwitzerlandcM, A3.17 Convenor The United StatesAlbert J. F.KeriAmerican Electric PowerRM JapanHirokiItoMitsubishi ElectricRM, A3.22 Convenor JapanTakeshiYokotaToshiba CorporationRM, B3.22 Convenor Member Name

26 26 Conclusion

27 27 Conclusion Sophisticated 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 C4.306 “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”.

28 28 Thank you !


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