Gwadà na Ƙarfafar Karkashin Aiki: Wani Tushen Ingantaccen Larzama da Ikkoda don Tsakiyar FC na Makarantar Yawan Kirkiro

I. Gwọrọ Ụzọ​

Ụzọ a na-eme ka gbanwee ike inye ụzọ ezi eme n'okpuru FC site na "High-Voltage Vacuum Contactors + High-Voltage Current-Limiting Fuses". Ọ bụkwa site n'ịkpeazụ na ịgbakwunye obere mgbochi ọnụ oyi, ụdị okpuru ọhụrụ, na ụdị capacitor banks n'okpuru 3kV ruo 12kV, dị ka ọ ga-enyere mmadụ maka ndepụta na mkpa ( dịka power plants, ụlọ ọrụ ndị kachasị, na mines). Nke a bụ ihe dị mkpa n'ebe a bụ ọtụtụ n'ime vacuum contactor na fuse current-limiting, enweghị ezi eme n'okpuru overload na short-circuit faults, ma bụghị nwere ọrụ dị elu, ọma, na akụkọ.

​II. Otu Na-ekwu Ihe Technical Characteristics​

​1. High-Voltage Vacuum Contactor (FC Circuit Operation and Overload Interruption Component)​​
High-voltage vacuum contactor bụ onye na-egosi ọrụ n'okpuru nke ọtụtụ nke ọrụ na ịkpeazụ overload currents. Ụfọdụ ihe dị ka:

• ​Core Structure:​​
• ​Vacuum Interrupter Chamber:​​ Enweghị ceramic enclosure na vacuum degree nke dị elu dị ka 1.33×10⁻⁴ Pa, nke na-enye ọrụ na ịkpọta arc n'ụbọchị a bụrụ na current zero-crossing, enweghị oil na ọrụ ọmụmụ.
• ​Insulation Mounting Bracket and Interlocking Mechanism:​​ Integrate fuse mounts na-enweghị interlocking trip mechanism. Mechanism a na-enye: ① Bụrụ na fuse n'ụdị phase kọrọ, ọ na-enye three-phase simultaneous trip nke contactor, ịkpọta single-phasing operation; ② Bụrụ na fuse n'ụdị phase adịghị, ọ na-enye mechanical lock nke contactor n'ịgbanwe, nkwado ọrụ ọmụmụ.
• ​Operating Mechanism:​​ Enweghị electromagnetic mechanism, na-enye ọrụ ọtụtụ nke ọrụ n'otu otu nke ọtụtụ nke ọrụ 2000 times/hour, dị elu nke ọrụ circuit breakers.
• ​Operation and Interruption Principle:​​
• ​Interruption Principle:​​ Enweghị high insulation na strong arc-extinguishing capability nke vacuum medium. Metal vapor arc nke ọrụ n'ịgbanwe na-enye ịkpọta instantaneously n'ụbọchị a bụrụ na current zero-crossing point, na-enye rapid dielectric strength recovery. Chopping current ya bụ nke dị elu 0.5A, na-enye suppression nke switching overvoltages, nke ọ dị ọma maka motor insulation.
• ​Holding Method:​​ Enweghị electrical self-hold (energy-saving, low noise) na mechanical self-hold (high reliability, anti-interference) methods. Users na-enye ọrụ maka operational requirements (e.g., LHJCZR series na-enweghị mechanical self-hold).
• ​Key Rated Parameters:​​

​2. High-Voltage Current-Limiting Fuse (FC Circuit Short-Circuit Protection Component)​​
High-voltage current-limiting fuse bụ nke na-ekwu ụzọ ụdị short-circuit faults. Ụfọdụ ihe dị ka:

• ​Core Function:​​ Enweghị instantaneous (quick-break) protection. Bụrụ na severe short-circuit fault na-eme (current exceeding the contactor's breaking capacity), fusible element ya na-enye ịkpọta na ịkpeazụ okpuru n'ụbọchị a bụrụ na current na-eme n'ịkpeazụ nke prospective peak. Ịkpeazụ time ya bụ nke dị elu (millisecond level), na-enye limitation nke fault current energy n'ọtụtụ, nkwado ụdị downstream equipment nke ọrụ.
• ​Basic Selection Principles:​​
• ​Rated Voltage:​​ Adịghị ịkọnye system's rated voltage, ịkpọta overvoltage nke na-eme n'fuse operation nke ọ dị elu insulation withstand level (typically limited to below 2.5 times the phase voltage).
• ​Rated Current:​​ Nwere ọrụ comprehensive consideration nke normal/overload currents, ụdị starting inrush characteristics (e.g., motor starting current, transformer magnetizing inrush), na ensuring selective coordination nke upstream protective devices (e.g., relays).
• ​Role Positioning:​​ Enweghị ụzọ ụdị backup protection n'okpuru FC. Normal overloads na smaller short-circuit currents na-enye comprehensive protection device signaling nke vacuum contactor n'ịkpeazụ. Fuse na-eme ọrụ n'ọtụtụ na fault current exceeding the contactor's breaking capacity ma ọ bụ contactor adịghị ịkpeazụ.

​III. Selection Guidance Based on Protected Object​

​1. Motor Protection Fuse Selection​
Motor starting currents bụ nke dị elu na durations long, na-enye ọrụ extra caution n'ịkpeazụ ịkpọta nuisance operation.

• ​Protection Coordination Logic:​​
• ​Overload Protection (e.g., stall, repeated starting):​​ Implemented by inverse-time relays, driving the contactor to open.
• ​Short-Circuit Protection:​​ Implemented by the fuse.
• ​Coordination Requirement:​​ The fuse's rated current must be greater than the motor's starting current, and its time-current characteristic curve must intersect the relay's curve at one point to achieve perfect coordination.
• ​Selection Reference (Excerpt):​​

• ​Key Point:​​ The longer the starting time and the higher the starting frequency, the larger the required fuse link rated current.

​2. Transformer Protection Fuse Selection​
Selection must ensure the fuse can withstand the transformer's closing magnetizing inrush current while providing effective protection against internal faults.

• ​Selection Reference (Excerpt):​​

​3. Capacitor Bank Protection Fuse Selection​
Capacitor bank switching generates high-frequency, high-amplitude closing inrush currents, posing special requirements for fuse selection.

• ​Special Consideration:​​ Must verify that the fuse can withstand the let-through energy (I²t) of the closing inrush current. Requirement: Inrush let-through energy < 0.7 times the fuse's minimum pre-arcing energy.
• ​Selection Requirements:​​
• Rated current is typically 1.5~2.0 times the capacitor's rated current.
• If the inrush current is too large, consider: ① Selecting dedicated capacitor fuses (e.g., WFN series); ② Adding a series current-limiting reactor with the capacitor; ③ Adding a series damping resistor in the branch.
• ​Recommendation:​​ A current-limiting reactor must be used when (Inrush Peak Current * Inrush Frequency) > 20000 or during extremely frequent operations.

​IV. Application Scope and Typical Cases​

​1. Application Scope​
The FC circuit solution is not universal. Its applicable boundaries are as follows:

• ​High-Voltage Motors:​​ ≤ 1200 kW
• ​Distribution Transformers:​​ ≤ 1600 kVA
• ​Capacitor Banks:​​ ≤ 1200 kvar
  Beyond these capacity ranges, a vacuum circuit breaker solution with higher breaking capacity and dynamic/thermal stability must be selected to ensure safety.

​2. Typical Case Validation​
This solution has been successfully applied in multiple projects, operating stably and reliably:

• ​Case 1: Chemical Plant, Texas, USA (Frequent Operation and Explosion-Proof Environment)​​
• ​Project Overview:​​ This large chemical base required frequent start-stop control for high-voltage pumps and compressor motors across multiple production lines, with environmental requirements for explosion-proofing and high reliability.
• ​Advantages Demonstrated:​​ The contactor's 2000 operations/hour frequency perfectly met process adjustment needs; precise coordination between the fuse and relay ensured accurate short-circuit protection for motors under frequent starting without nuisance operation; the low chopping current (<0.5A) provided by the vacuum interrupter effectively suppressed switching overvoltages, protecting the insulation of older motors. The overall solution saved significant investment compared to vacuum circuit breaker switchgear.
• ​Case 2: Automotive Manufacturing Plant, Bavaria, Germany (Transformer and Capacitor Compensation Protection)​​
• ​Project Overview:​​ A new smart manufacturing factory required stable, high-quality power supply for numerous robotic servo systems on automated production lines, accompanied by multiple dry-type distribution transformers and capacitor compensation banks.
• ​Advantages Demonstrated:​​ Fuse rated current selection fully considered transformer magnetizing inrush characteristics, avoiding nuisance operation during closing. For the capacitor banks, dedicated fuses successfully withstood the closing inrush impact (I²t verification passed). The contactor's low bounce ensured capacitor switching without re-ignition, safeguarding power quality on the grid.

​V. Solution Advantage Summary​

1. ​High Reliability:​​ Vacuum interrupter chamber is maintenance-free with a mechanical life of up to millions of operations; fuses provide millisecond-level quick-break protection.
2. ​Strong Safety:​​ Mechanical interlocking mechanism prevents single-phasing operation and closing with potential hazards; low chopping current protects equipment insulation.
3. ​Good Economy:​​ Compared to vacuum circuit breaker switchgear, FC switchgear offers lower cost, smaller size, and extremely high cost-effectiveness.
4. ​Intelligence:​​ Contactors can be seamlessly integrated with microprocessor-based protection devices, enabling remote monitoring, intelligent control, and data upload.
5. ​Easy Maintenance:​​ Core components are designed for maintenance-free operation; after fuse operation, only replacement with a same-specification fuse link is required, making operation simple.