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Standardization Aspects in UHV Networks

Standardization Aspects in UHV Networks. Denis Dufournet. New Delhi, January 2009. Chairman IEC TC17 Member CIGRE WG A3-22. Standardization Aspects in UHV Networks Introduction.

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Standardization Aspects in UHV Networks

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  1. Standardization Aspects in UHV Networks Denis Dufournet New Delhi, January 2009 Chairman IEC TC17 Member CIGRE WG A3-22

  2. Standardization Aspects in UHV NetworksIntroduction • Following a recommendation by IEC Sector Board 1 in February 2006, IEC SMB has requested the relevant Technical Committees in IEC to produce or revise their standards for UHV. • First Symposium was organized in Beijingin July 2007 by IEC, CIGRE and State Grid Company of China. • During this Symposium, it was concluded that the technology is mature enough so that standardization can be done urgently to coincide with starting projects in China and India. • Workshop on UHV organized in January 2008 by Powergrid Corporation of India. • IEC TC17 asked CIGRE Study Committee A3 to provide the technical requirements for switchgear with rated voltages exceeding 800 kV. • CIGRE Working Group A3-22 was set up and provided the technical information at the end of 2008. • IEC SC17A (high-voltage switchgear and controlgear) and SC17C (assemblies of high-voltage switchgear and controlgear) will start the revision of their standards for UHV beginning of 2009.

  3. Work of CIGRE A3-22 ̋ Technical requirements for substation equipment ̋

  4. Standardization Aspects in UHV NetworksWork of CIGRE A3-22 • WG A3.22 was set up to recommend technical requirements for UHV substation equipment: switchgear and controlgear, power transformer, VT/CT, and MOSA. • First Technical Brochure covers state-of-art specifications of substation equipment exceeding 800 kV, including field experience of various projects. • A second Technical Brochure will summarize all technical specifications of substation equipment

  5. Standardization Aspects in UHV NetworksWork of CIGRE A3-22: Circuit Breakers • TRV for terminal faults • First pole to clear factor: kpp = 1.2 • Short-line-fault • Line surge impedance: Z= 330 Ώ • DC time constant • Recommended value: L/R= 120 ms • Transformer limited faults • TRV with time t3 given by with k= 6.0 • Out-of-Phase k= 2.0 • Capacitive current switching: voltage factor = 1.2 and 1.4

  6. Standardization work by IEC Subcommittee 17A

  7. Standardization Aspects in UHV NetworksWork by IEC SC17A • IEC SC17A (high-voltage switchgear and controlgear) and SC17C (assemblies of high-voltage switchgear and controlgear) will start the revision of their standards for UHV beginning of 2009. • The following standards will be revised: • IEC 62271-1 (Common specifications), • IEC 62271-100 (Circuit-breaker), • IEC 62271-101 (Synthetic testing), • IEC 62271-102 (A.C. Disconnectors and earthing switches), • IEC 62271-110 (Inductive load switching). • In addition it will be necessary to standardize requirements for high-speed earthing/grounding switches and to update the application guide for high-voltage circuit breakers. • The revision of IEC documents will be made using the technical data and recommendations by CIGRE WG A3-22 and the standardization of insulation levels that is prepared by IEC TC28. • Additional input from CIGRE A3-22 may be required (e.g. HSGS). • It is expected that the revised standards will be produced before end of 2012.

  8. Considerations on Standardized TRVs for UHV Circuit Breakers

  9. Standardization Aspects in UHV Networks TRVs for UHV Circuit Breakers • TRVs for terminal faults and transformer limited faults (TLF) T100: an amplitude factor of 1.5 should be required to cover calculated TRVs (1.46). A conservative value needed due to the reduced number of TRV simulations available. Alternatively, kpp can be 1.3 and kaf = 1.4 (same TRV peak). T10: in IEC 62271-100 it covers also TRVs for Long Line Faults TLF should be covered separately (as in IEEE C37.06)

  10. Standardization Aspects in UHV Networks TRVs for UHV Circuit Breakers • TRVs for terminal faults

  11. Standardization Aspects in UHV NetworksTRVs for UHV Circuit Breakers • TRVs for terminal faults • Rated values of TRVs in section 4 of IEC 62271-100 represent system values. • They do not take into account modifying effects by the circuit- breaker i.e. possible peak and RRRV reduction by opening opening resistors, capacitors. • MOSA have an influence on the TRV peak as protective levels are optimized at UHV, however the following has to be considered • A margin is necessary to cover variations in clipping levels by MOSA. Another margin is necessary between the circuit breaker TRV withstand and the clipping level ; • TRV peak for terminal fault T100: 1.2 x 1.5 = 1.8 p.u., there is a 10% or 6% margin compared with a surge protective level of 1.63 or 1.7; • MOSA affects the TRV peak for terminal faults at 10% and 30% of rated short-circuit current, but not the TRV for long line faults. As a consequence TRVs for T10 and T30 (that cover both types of faults in IEC 62271-100) are not affected. Based on these considerations, for surge protective levels of 1.63-1.7, MOSA do not affect standard values of TRVs.

  12. Standardization Aspects in UHV NetworksTRVs for UHV Circuit Breakers • TRVs for terminal faults • Synthetic circuits have to be used necessarily for making and breaking tests. New test circuits are designed to produce the required TRVs for UHV. Voltage injection is normally used to meet the requirements for the TRV with long time to peak (t2) and for the recovery voltage. But, It is mandatory to verify interruption in the thermal phase by current injection. • Tests have to be defined for circuit breakers with opening resistors in IEC 62271-100 (Circuit-breakers) and to be covered more detail in IEC 62271-101 (Synthetic testing).

  13. Standardization Aspects in UHV NetworksTRVs for UHV Circuit Breakers • Transformer limited faults (TLF) • Severe TRV conditions may occur when a terminal fault is fed through a transformer without any appreciable capacitance between the transformer and the circuit breaker. • In such cases, the rate-of-rise of recovery voltage (RRRV) may exceed the values specified in the standards for terminal fault test duty T10 • The system TRV can be modified by a capacitance and then be within the standard TRV capability envelope. As an alternative, the user may choose to specify a circuit breaker having a TLF breaking capability. • CIGRE A3-22 recommends to choose a TLF breaking current value in the R10 series (e.g. 6.3-8-10-12.5 kA), the closest to the actual value calculated for the application. • As done already for rated voltages less than 100 kV, TRV values for TLF should be given in a normative annex.

  14. Standardization Aspects in UHV NetworksConclusion • Extensive work has been done over the past two years in CIGRE SC A3 to study the technical requirements for substation equipment with rated voltages exceeding 800 kV. • Based on the result of these studies, CIGRE A3-22 has made recommendations to IEC TC17. • Standardization work for UHV has started in IEC with the definition of insulation levels by TC28. • The revision of IEC TC17 standards starts beginning of 2009 with the objective of having the revised standards before the end of 2012. • It will represent a significant amount of work that will be done by seven maintenance teams (MT), project team (PT) or working groups (WG). • In order to do a fast and efficient work, the present memberships of MT’s or WG’s in IEC SC17A should be completed by additional experts from countries having UHV projects or experience.

  15. Thank you for your attention

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