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TRANSMISSION SYSTEM

SPECIAL PROTECTION SCHEMES IN OPERATION AT ITAIPU POWER PLANT RUI JOVITA G. C. DA SILVA * JOSÉ BENEDITO MOTA JÚNIOR ROBSON ALMIR DE OLIVEIRA JOSÉ GREGÓRIO ACHA NAVARRO MARCELINO PEREIRA DE ALMEIDA EVONYR BORDIN FILHO FERNANDO VEGA DAHER ALEXANDRE GONÇALVES LEITE. TRANSMISSION SYSTEM. 6.300 MW.

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TRANSMISSION SYSTEM

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  1. SPECIAL PROTECTION SCHEMES IN OPERATION AT ITAIPU POWER PLANTRUI JOVITA G. C. DA SILVA *JOSÉ BENEDITO MOTA JÚNIORROBSON ALMIR DE OLIVEIRAJOSÉ GREGÓRIO ACHA NAVARRO MARCELINO PEREIRA DE ALMEIDAEVONYR BORDIN FILHOFERNANDO VEGA DAHERALEXANDRE GONÇALVES LEITE CIGRE 2006 - B5-203

  2. TRANSMISSION SYSTEM 6.300 MW 23 % 7.000 MW 94 % 1.300 MW 6.300 MW 6 % 90 % CIGRE 2006 - B5-203

  3. INSTALLED CAPACITY EVOLUTION: GENERATION X TRANSMISSION.50 Hz Sector CIGRE 2006 - B5-203

  4. INSTALLED CAPACITY EVOLUTION: GENERATION X TRANSMISSION.60 Hz Sector CIGRE 2006 - B5-203

  5. DESCRIPTION OF THE SPECIAL PROTECTION SCHEMES 60 HZ - 17 ACTIONS50 HZ - 14 ACTIONS stability 7 overfrequency 5 self-excitation 1 frequency collapse 3 overvoltage 1 overvoltage 4 overfrequency 3 overload 2 overload 3 voltage collapse 1 damping 1 CIGRE 2006 - B5-203

  6. Frequency Rate Scheme CIGRE 2006 - B5-203

  7. SCHEME TO AVOID FREQUENCY COLLAPSE CIGRE 2006 - B5-203

  8. OVERLOAD ON LINES CIGRE 2006 - B5-203

  9. PERFORMANCE 60 Hz 50 Hz Time to re-synchronize switches manuallywas reduced about 5 min. controlledIts 1 min 30 s now. => self-excitation => operators are more familiarized CIGRE 2006 - B5-203

  10. PERFORMANCE 60 Hz 159 PLCs actuations 13 errors - associated with maintenance, PLCs design and auxiliary equipments failures. CIGRE 2006 - B5-203

  11. PERFORMANCE 60 Hz CIGRE 2006 - B5-203

  12. PERFORMANCE 60 Hz CIGRE 2006 - B5-203

  13. PERFORMANCE60 Hz SCHEMES INDEPENDENT FROM PLCs:* scheme against self-excitation - one correct actuation during 2002 major blackout. * scheme to increase damping with Brazil Southern region - one correct actuation during an opening of 765 kV S-SE interconnection.* scheme to control overfrequency in Brazil Southern region - one incorrect actuation in 1994 during relay maintenance, tripping all 765 kV lines in Foz do Iguaçu substation. CIGRE 2006 - B5-203

  14. PERFORMANCE50 Hz scheme to avoid the separation of the interconnected system Itaipu-Ande – two correct actuation, with generating unit tripping by frequency rate to control overfrequency. CIGRE 2006 - B5-203

  15. PERFORMANCE50 Hz One was during the 1999 major blackout, and the interconnection Itaipu-Ande was opened by the actuation of the 220 kV overvoltage relay (overvoltage above 286 kV for more than 1s), causing blackout in Ande power system.Because of this occurrence the scheme to avoid frequency collapse in the Ande power system was created. The other actuation avoids blackout in Ande power system during HVDC bipole blocking. CIGRE 2006 - B5-203

  16. PERFORMANCE50 Hz About SPSs incorrect actuation, there were only one, which occurred in 1995 during maintenance, when there was an accidental operation of the 500 kV line protection, signalizing a two-phase fault. This resulted in interconnection Itaipu-Ande opening and blackout in Ande power system. CIGRE 2006 - B5-203

  17. CONCLUSIONS Despite the number of Special Protection Schemes installed at Itaipu power plant, they can be characterized by their simplicity and good performance. They were installed since the beginning of plant operation and have been provided security to the electrical system and equipments. CIGRE 2006 - B5-203

  18. CONCLUSIONS Most of SPSs are designed to act during complex problems in the interconnected system, the exception are the SPSs implemented by PLCs in 60 Hz system, which act during simple contingencies too. The SPSs actuations avoided interruption of load, or even major blackout, throughout Brazilian and Paraguayan power system, mainly those designed to maintain system stability and to avoid voltage and/or frequency collapse. CIGRE 2006 - B5-203

  19. CONCLUSIONS It´s important to highlight the familiarization of Itaipu operators with all these schemes and their actuations, characterized mainly by the right auxiliary switches positioning, on 50 Hz sectors, and by the short period to re-synchronize generating units disconnected by SPSs, in 60 Hz sector. CIGRE 2006 - B5-203

  20. CONCLUSIONS The SPSs have been presented very good performance. The misoperations are associated with equipment maintenance and with failures of PLCs design or auxiliary equipments. The SPSs implemented by PLCs present less than 10 % of incorrect actuations and/or refusals. The others SPSs have so few actuations to allow a statistics calculation, but the incorrect actuations didn’t repeat for years. CIGRE 2006 - B5-203

  21. SPECIAL REPORT Question 2.3How important are communication issues (availability, reliability, etc.) for the implementation of SPS ?Deve-se procurar alcançar uma disponibilidade o mais próxima possível de 100 % para os recursos de comunicação utilizados em SPS. Qualquer redução implica em indisponibilidade do SPS. O mesmo vale para uma recepção correta do sinal enviado. Para garantir isso pode-se enviar os sinais por meios diferentes. CIGRE 2006 - B5-203

  22. SPECIAL REPORT Question 2.3Have any risk been identified involving overfunction in case of duplication/triplication of equipments ?É uma possibilidade. O projeto do SPS deve sempre prever que a sua possibilidade de falha deve ser mínima face a solicitação mais crítica. Assim, uma duplicação/triplicação tem o objetivo de evitar atuações desnecessárias, mas não podem aumentar a possibilidade de falha na pior condição. CIGRE 2006 - B5-203

  23. SPECIAL REPORT Question 2.3Have any misoperation been experienced that have had an influence on decision concerning systems’ maintenance ?Sim. Muitas. As rotinas e procedimentos de manutenção dos SPSs requerem determinadas condições do sistema que muitas vezes podemimplicar em restrições eltro-energéticas. CIGRE 2006 - B5-203

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