Tarihin Mai Guje da Yanzu na Mafi Fadada Vacuum Circuit Breakers
Makaranta Masu Kirki Mai Tsawon Dukkun Daban-Daban: Bayanin
Bayani
Makaranta masu kirki mai tsawon dukkan-daban (HV VCBs) suna samu zama tushen da yake da gaba a matsayin wata na tushen makaranta masu SF6 gas-insulated circuit breakers, musamman a tattalin aiki da ake bukatar kisan kirkira da ma'ana da adadin lalacewa. Daga baya 2014, HV VCBs suna cikin kusan da suka amfani a matsayin tushen masu kirki mai tsawon dukkan-daban, wanda ya ba amsa mai karfi da daidai a lokacin da ake yi aiki da kisan kirkira da ma'ana da adadin lalacewa.
An yi amfani da switchgear masu tsawo a tattalin aiki da kasa har zuwa shekaru 30, musamman don kirkiri da tsaro mai tsawon dukkan-daban da kuma kirkira muhimma. Ingantaccen amincewa da nuna masu tsawo a tsarin tsawon dukkan-daban mai tsawon dukkan-daban (har zuwa 52 kV) ce ta fi yawa, wanda ya ba muke tsarin tsawo a tattalin aiki da kasa. Amma, abubuwan da ake yi don koyar da tsarin tsawon tsawo zuwa tsarin tsawon dukkan-daban sun faru a baya 1960, da nasarorin muhimmiyar da aka yi rarrabe a baya 1980 inda an saka wa makaranta masu tsawon dukkan-daban na tsawon dukkan-daban a Japan. Har zuwa 2010, kadan 10,000 HV VCBs suna yi aiki, musamman a tattalin aiki na kayan aiki amma kuma a tattalin aiki na gwamnati. Rike masu tsawo a matsayin tushen masu tsawo suna samu zama saboda kyau a yi kisan kirkira da ma'ana da adadin lalacewa.
A Amurika, an yi amfani da capacitor bank switches masu tsawo zuwa shekaru dubu a tsarin tsawon dukkan-daban har zuwa 242 kV. A baya 2008, wasu harkokin yanayi da kuma harkokin giniyar (R&D) a China da Turai suna neman don fadada HV VCBs, da muhimmanci a kan koyar da amfani da SF6. Wannan ya ba amsa masu aiki da suka iya yi aiki a tsarin tsawon dukkan-daban har zuwa 145 kV. A China, yanayin amfani da HV VCBs a tattalin aiki na kayan aiki zai ci gaba, da kadan 100 unit suna yi aiki a tsarin tsawon dukkan-daban har zuwa 126 kV. A Turai, an yi tasirin a kan fitaccen aiki don tabbatar da nuna masu aiki bayan idan an yi aiki a labaran fitaccen aiki.
Teknologi da Tashin
Duka masu aiki na HV VCB suna da nasarorin a tsarin masu aiki na tsawon dukkan-daban na tsawon dukkan-daban, wanda an yi koyar da shi a ranar. Ba a bukata nasarorin teknologi mai tsari don koyar da shi zuwa tsarin tsawon dukkan-daban masu. Abin da ke ciki ita ce koyar da tashin interrupter don koyar da tsarin tsawon dukkan-daban. Misali, ya kamata koyar da tsari da kuma tsari da take sa a kan tsawon dukkan-daban zuwa tsarin tsawon dukkan-daban har zuwa 52 kV. A wasu hali, zuwa tsarin tsawon dukkan-daban har zuwa 126 kV, ana amfani da biyu vacuum gaps a kan tsarin series don tabbatar da nuna masu aiki.
Nuna Masu Aiki
Kirki Mai Yawance: Don kisan kirki mai yawance har zuwa 2,500 A, ba a nan wannan mutane da ke ciki a nan HV VCBs da SF6 circuit breakers. Amma, ya kamata koyar da kisan kirki mai yawance (har zuwa 2,500 A) a HV VCBs saboda kirki mai tsawo daga tsarin contact structure da kuma tsarin heat transfer na interrupter.
Tabbataccen: Ya kamata a tabbatar da tsarin medium masu aiki a SF6 circuit breakers, saboda tsarin vacuum a HV VCBs ba za a iya tabbatar da shi a kan aiki.
Kirki: HV VCBs suna iya yi kisan kirkira masu aiki da kuma kudin aiki saboda tsarin vacuum contact system da ke da aiki da arcing. Wannan ya ba amsa masu aiki masu tsawo saboda aiki da kisan kirkira, misali a kisan kirkira na kowace rana.
Energy Masu Aiki: A tsarin 72.5 kV, energy masu aiki da ke bukata a vacuum circuit breaker ce ta fi yawa--kadan 20% daga wadannan da ke bukata a SF6 circuit breaker. Tsarin kafin aiki na biyu suna da nasarori.
Interrupter Configuration: Zuwa tsarin tsawon dukkan-daban har zuwa 145 kV, HV VCBs suna bukata biyu vacuum gaps a kan tsarin series, amma SF6 technology suna da nasarorin a yi single-break circuit breakers har zuwa 550 kV tun daga 1994, wanda suna da amfani a kudancin kasashe.
Arc Characteristics: Tsarin arc voltage a HV VCBs ce ta fi yawa a nan SF6 circuit breakers, kadan tens of volts har zuwa hundreds of volts a SF6. Kuma, tsarin duration of the arc during fault switching ce ta fi yawa a vacuum switchgear, kadan 5-7 ms har zuwa 10-15 ms a SF6 circuit breakers. Wannan ya ba amsa kisan kirkira masu aiki da kuma kudin aiki a HV VCBs.
X-ray Emissions: HV VCBs zuwa tsarin tsawon dukkan-daban har zuwa 145 kV suna koyar da X-rays a kan tsarin standardized limit of 5 µSv/h a kan aiki da kusa. SF6 circuit breakers ba suna koyar da X-rays.
Nuna Masu Aiki
Interruption Fault Current: HV VCBs suna da nasarorin a kirkiri fault currents da kudin aiki da transient recovery voltage (TRV) saboda tsarin dielectric recovery, wanda ya fi yawa a nan SF6 circuit breakers.
Breakdown Statistics: Idan vacuum gaps suna da nasarorin breakdown voltages, akwai tsari da ke ciki a kan breakdown at relatively moderate voltages. Vacuum gaps suna iya yi spontaneous late breakdown, wanda ya faru zuwa shekaru milliseconds a kan current interruption. Amma, abubuwan da ke faru a kan wannan suna da nasarori saboda vacuum gap ya ci gaba a kan insulation. Imkanin abubuwan da ke faru a kan late breakdown ba suka tabbata ba.
Inductive Load Switching: A tattalin aiki da inductive loads, misali shunt reactor switching, HV VCBs suna iya yi kisan repeated re-ignitions a kan power frequency current zero. Wannan suna da nasarorin a kirkiri high-frequency currents da ke faru a kan re-ignition. Abubuwan da ke faru a kan re-ignition transients a interacting apparatus, misali RC snubbers da metal-oxide arresters, suna da aiki a kan yanayi.
Capacitor Bank Switching: A kirkiri capacitor banks, ya kamata koyar da kisan inrush currents, saboda suna iya koyar da tsarin dielectric properties da contact system. Wannan tsarin suna da amfani a HV VCBs da SF6 circuit breakers. Mitigation strategies sun haɗa da amfani da series reactors ko controlled switching, amma akwai nasarori a kan field experience a kan HV VCBs.
Future Prospects and Market Perception
A survey conducted among users of high-voltage switchgear revealed that the absence of SF6 is seen as the primary advantage of vacuum switchgear, provided that the external insulation is also SF6-free. However, the lack of extensive service experience at transmission voltage levels remains a significant hesitation for the widespread adoption of HV VCBs. Despite this, the environmental benefits and operational advantages of vacuum technology are driving continued interest and development in this area.
Potential users of high voltage vacuum circuit breakers (HV VCBs) frequently raise concerns about the generation of overvoltages due to current chopping and the possibility of X-ray emissions during switching operations. These issues are critical for ensuring the safe and reliable operation of HV VCBs, especially as they are increasingly considered for transmission voltage applications.
X-ray Emission
For single-break devices, X-ray emissions from HV VCBs with rated voltages up to and including 145 kV remain well below the standardized limit of 5 µSv/h under normal operating conditions. Multiple-break devices exhibit even lower levels of X-ray emissions. This is an important consideration for regulatory compliance and safety, as it ensures that HV VCBs can be deployed without posing significant radiation risks to personnel or the environment.
Pilot Projects
A large majority of respondents expressed a strong interest in initiating pilot projects to gain practical experience with HV VCB technology. Such projects would allow utilities and system operators to evaluate the performance, reliability, and operational characteristics of HV VCBs in real-world conditions. Solidly earthed networks are recommended for these pilot projects, as the network conditions in medium voltage systems are not always comparable to those in transmission voltage networks, particularly regarding earthing conditions. This approach will help ensure that the experiences gained are relevant and applicable to transmission-level applications.
Standardization
The current IEC circuit breaker standard, IEC 62271-100, has a strong focus on SF6 switching technology, which may not fully address the unique characteristics and challenges of vacuum switching. For example, test duties that are challenging for SF6, such as short-line fault tests, may not be as critical for vacuum technology. Conversely, the application of continuous recovery voltage in synthetic testing, which is less relevant for SF6, could be more important for demonstrating the absence of late breakdown in vacuum interrupters. As HV VCBs gain more traction, there may be a need to revise or supplement the existing standards to better accommodate vacuum technology.
Technical Implications of SF6-Free Design
When SF6 is absent as an external insulating medium, other technical implications must be considered. For instance, alternative insulation methods may require higher pressure, increased weight, larger footprint, or different design considerations to ensure adequate insulation performance. Manufacturers are actively exploring these alternatives to develop viable replacements for SF6, but until a new technology that can cover all voltage ratings is found, SF6 will likely remain essential for certain transmission network applications.
Manufacturer Commitment
Manufacturers are committed to developing and making available industrially viable alternatives to SF6 technology. While SF6 has been the dominant insulating gas for high-voltage applications due to its excellent dielectric properties, the environmental concerns associated with SF6, particularly its high global warming potential, have driven the search for greener solutions. HV VCBs represent one such solution, offering a sustainable alternative for applications where frequent switching and lower maintenance are required. However, the transition away from SF6 will be gradual, as manufacturers continue to innovate and refine new technologies to meet the diverse needs of the power industry.
