Pangangalang Patalim para sa Sirkwitong FC sa 3~12kV na Sistema ng Auxiliary Power: disenyo pagpili at mga kaso ng aplikasyon

I. Buhatan sa Solusyon​
Ang solusyon ini nga naglalayong mohatag og kompletong sistema batas sa pagkombinado sa high-voltage vacuum contactor (Contactor) ug high-voltage current-limiting fuse (Fuse), nga gikatakdang FC circuit. Gidisenyo alang sa mga medium-voltage system nga nagsugyot gikan sa 3 hangtod sa 12 kV, maayo ni para sa mga aplikasyon nga nagkinahanglan og paborito nga operasyon, mataas nga reliabilidad, ug ekonomiko. Sa FC circuit, ang vacuum contactor ang nag-atiman sa pagbuhat ug pagputli sa normal ug overload currents, sama sa paborito nga mga operasyon, samtang ang high-voltage fuse ang naghatag og matigas nga short-circuit protection. Bisanhin, sila nagbuhat isip usa ka fully functional, high-performance protection ug control unit.

​II. Katungod sa Core Components​
Ang core advantage sa FC circuit nahimutang sa extraordinary nga performance ug precise coordination sa duha ka key components.

​​(I) High-Voltage Vacuum Contactor (Operation and Overload Interruption Component)​​
Isip operational core sa circuit, ang vacuum contactor adunay sumala nga katungod:

1. ​Advanced Structure and Interruption Principle:​​
• Nagpadako og vacuum interrupter chamber (vacuum level up to 1.33×10⁻⁴ Pa) uban sa iyang main contacts sealed within a ceramic enclosure. Durante sa pagbukas, ang moving ug fixed contacts separate rapidly, leveraging the rapid condensation of metal vapor at current zero-crossing to efficiently extinguish the arc ug restore insulation strength.
• Equipped with a linked tripping mechanism that ensures tripping upon the melting of one fuse phase, preventing phase-loss operation, ug includes a mis-closing prevention function when fuses are not installed.
• Extremely low chopping current (≤0.5A), effectively suppressing switching overvoltages ug protecting the insulation of inductive loads such as motors.
2. ​High-Reliability Operating Mechanism:​​
• Utilizes an electromagnetic operating mechanism capable of switching frequencies up to 2,000 operations per hour, meeting the most demanding frequent operation requirements.
• Flexible holding methods: Electrical self-holding (maintained by a holding coil after closing, with low power consumption) ug mechanical self-holding (e.g., LHJCZR series, mechanically latched after closing, requiring no continuous power supply) are available to suit different control needs.
• Strong compatibility with control power sources, supporting DC/AC 110V/220V.
3. ​Excellent Rated Parameters and Lifespan:​​
• Key electrical parameters:

• Extended lifespan: Electrical life of up to 300,000 operations ug mechanical life of up to 1,000,000 operations, significantly reducing maintenance efforts ug lifecycle costs.
• Dedicated vacuum interrupter chambers: Such as the TJC 12/630 type, featuring low loss, low surge, high wear resistance, ug a contact resistance of ≤60 μΩ.

​​(II) High-Voltage Current-Limiting Fuse (Short-Circuit Protection Component)​​
As the core of short-circuit protection in the circuit, its selection and application are critical.

1. ​Functional Principle:​​ When the current exceeds a specified value for a certain duration, the fuse element melts instantly and interrupts the fault current. Its key characteristic is that the larger the interrupting current, the shorter the operating time, providing strong current-limiting capability.
2. ​Selection Principles:​​
• Rated voltage: Must be no less than the system's rated voltage; it can be slightly higher but must never be lower.
• Rated current: Must comprehensively consider the circuit's normal operating current, overload current, ug equipment starting characteristics (e.g., motor starting current ug time). As a backup protection, it operates only when the fault current exceeds the contactor's breaking capacity or if the contactor fails to operate.
3. ​Protection Coordination with Different Equipment:​​
• High-voltage motors (≤1200 kW): The fuse must withstand the motor's starting current, while overload protection is handled by a comprehensive protection relay. Ensure the fuse's time-current characteristic curve intersects correctly with the relay curve to achieve protection division.
• Example: For a 250 kW motor with a starting time of 6s ug starting current of 220A, a 100A fuse element is suitable (for 2-3 starts per hour).
• Transformers (≤1600 kVA): The fuse must withstand inrush currents during energization ug sustained overload currents. Selection is directly matched based on the transformer's rated capacity ug voltage level.
• Example: For a 10 kV/800 kVA transformer, an 80A fuse is suitable.
• Capacitor banks (≤1200 kvar): Must withstand switching inrush currents, ug their let-through energy must be less than the capacitor's withstand capability. The rated current is typically 1.5–2 times the capacitor's rated current. For applications with excessive inrush currents or frequent switching, series reactors are recommended.

​III. Application Scope ug Typical Cases​

​​(I) Application Scope​

• ​Suitable Scenarios:​​
• Protection ug control circuits for transformers up to 1600 kVA in industrial plants.
• Frequent starting ug protection circuits for high-voltage motors up to 1200 kW.
• Switching circuits for capacitor banks up to 1200 kvar.
• ​Unsuitable Scenarios:​​ For loads exceeding the above capacities, vacuum circuit breaker panels must be used.

​​(II) Successful Cases​
The FC circuit solution has been widely applied in numerous power plant projects, with proven reliability:

1. ​Thermal Power Plant:​​ Utilized 8 vacuum circuit breaker panels + 36 FC panels. Among them, LHJCZR contactors with WFNHO fuses protect motors, while XRNT fuses protect transformers.
2. ​Power Plant:​​ Utilized 10 vacuum circuit breaker panels + 36 FC panels (21 for motor protection, 12 for transformer protection, ug 3 for capacitor protection).

​IV. Solution Advantages ug Conclusion​
This FC circuit solution integrates the dual advantages of vacuum contactors ug current-limiting fuses, offering the following core benefits:

1. ​Cost-Effectiveness:​​ Significantly lower investment costs compared to vacuum circuit breaker panels, offering high cost-performance.
2. ​Specialized Performance:​​ Contactors excel in frequent operations ug overload interruption, while fuses excel in rapidly interrupting high short-circuit currents, ensuring clear division of labor ug superior protection.
3. ​Safety ug Reliability:​​ Extremely short short-circuit interruption time (millisecond level), excellent current-limiting characteristics, ug effective protection of system equipment. The linked tripping mechanism prevents phase-loss operation.
4. ​Maintenance-Free ug Long Lifespan:​​ Vacuum interrupter chambers are maintenance-free, with electrical ug mechanical lifespans of up to a million operations, significantly reducing lifecycle costs.
5. ​Compact ug Flexible Design:​​ Compact structure saves installation space. High versatility allows interchangeability among similar products, facilitating maintenance ug spare parts management.

​Conclusion:​​ The FC circuit is an ideal choice for the protection of small to medium-capacity transformers, motors, ug capacitors in industrial power systems such as power plants, petrochemicals, ug metallurgy. This solution is technologically mature, extensively validated, ug offers outstanding advantages, making it the best practice for balancing performance, cost, ug reliability. For applications exceeding its capacity range, vacuum circuit breaker solutions are recommended.