Serye Resonante Fault Current Limiter Batasado sa mga Konbensional nga Komponente: Isang Ekonomiko ug Reliableng Solusyon sa Short-Circuit Current

13yrs + staff 30000+m² US$100,000,000+ China

Introduction: Research Background and Core Objectives

Gravedad ng Problema sa Short-Circuit Current
Tungod sa patuloy nga pagdako sa sakop ug kapasidad sa power grid, ang lebel sa short-circuit current sa sistema nagsu-on na kaayo, naglakip o higayon nang lampa sa mga limitasyon sa umiunong equipment.
• Data Support: Ang monitoring nagpakita nga ang inila-ila nga short-circuit current sa pipila ka 500kV, 220kV, ug 10kV substations sa nasud nagsu-on na ngabot sa 100 kA; ang pinaka taas nga periodic component sa short-circuit current sa major power sources nakahanas sa 300 kA.
• Serious Hazards: Ang napakataas nga short-circuit currents nagresulta sa kakulangan sa maayo nga high-voltage circuit breaker models, nagdala og pinsala sa electrical equipment tungod sa paglampa sa thermal ug electrodynamic force limits, ug mahimo usab nga magdala og safety issues sama sa electromagnetic interference sa communication systems, ground potential rise, ug step voltage. Kini naging key technical bottleneck nga nagbatasan sa safe ug economical development sa power grid.
Limitations of Existing FCL Technologies
Ang kasamtangan nga mainstream fault current limiter (FCL) technologies adunay inherent drawbacks, nagpadali sa large-scale application:
• Superconducting FCL: Nagdepende sa superconducting materials, isip usa ka technology nga dili pa maturog, adunay low reliability, adunay taas nga operation ug maintenance costs, ug wala ekonomical, nagpadali sa iyang engineering application sa short to medium term.
• Power Electronic FCL: Limitado sa voltage withstand ug current-carrying capacity sa power semiconductor devices, nahahamon sa series/parallel voltage ug current sharing control, adunay komplikado nga system structure (nanginahanglan og additional current-limiting components ug fast protection circuits), ug mahal.
Core Objective of This Research
Arangkada sa pag-address sa uban nga issues, kini nga study nagmatamay sa pag-proposal og usa ka series resonant fault current limiter solution batas konventional nga electrical components, nga non-superconducting ug non-power electronic. Specifically, duha ka topologies gipag-estudyahan:
Series Resonant FCL based on a Saturable Reactor
Series Resonant FCL based on a ZnO Arrester
Kini nga research mogamit og Electromagnetic Transients Program (EMTP) simulation aron masukod ang ilang transient current-limiting characteristics, perform a comparison, ug ultimately verify their significant advantages in technical feasibility, economy, ug operational reliability.

II. Series Resonant FCL Based on Saturable Reactor

Circuit Topology and Working Principle
• Topology Structure: Ang core consist of a saturable reactor L_B, a capacitor C, ug a series reactor L. L_B connected in parallel with C, ug this combination is then connected in series with L into the system.
• Working Principle:
o Normal Operation: The line current is small. L_B operates in the unsaturated region (its equivalent inductance L_B1 is very large). Its parallel combination with C behaves inductively. Together with the series reactor L, they satisfy the power frequency series resonance condition (ωL - 1/ωC ≈ 0). The device presents very low impedance, resulting in minimal system losses.
o Fault State: A surge in short-circuit current rapidly saturates L_B (its equivalent inductance drops sharply to L_B2). Its parallel branch effectively short-circuits capacitor C, thus breaking the resonant condition. At this point, the series reactor L and the saturated reactor L_B2 are both inserted into the system, effectively limiting the short-circuit current.
o Fault Clearance: After the fault is cleared, the current decreases. L_B automatically exits saturation, the capacitor is re-engaged, and the circuit returns to the resonant state, achieving self-triggered switching without an external power source.
• Parameter Selection Principles:
o ω²L_B1C >> 1 (Ensures the parallel branch behaves inductively during normal operation)
o ωL - 1/ωC ≈ 0 (Satisfies the resonance condition for normal operation)
o ω²L_B2C << 1 (Ensures the parallel branch behaves capacitively during a fault, effectively shorting the capacitor)
Current-Limiting Characteristic Simulation Analysis (EMTP)
Simulation was conducted under a single-phase-to-ground short-circuit fault condition in a 220kV system (prospective short-circuit current peak: 110kA). Key conclusions are as follows:

Influencing Factor	Core Conclusion	Typical Simulation Data (Example)
1. Unsaturated Inductance L_B1	Increasing L_B1 significantly reduces capacitor overvoltage but has little effect on short-circuit current; effect saturates.	L_B1=1317mH: Capacitor voltage 270kV; L_B1=1321mH: Capacitor voltage 157kV (42% decrease)
2. Saturated Inductance L_B2	An optimal range exists (1-7mH). Too small gives poor limiting; too large causes severe capacitor overvoltage.	L_B2=7mH (C=507μF, L=20mH): Short-circuit current 25kA, Capacitor voltage 157kV
3. C/L Parameter Coordination	An optimal combination exists to cooperatively control short-circuit current and capacitor overvoltage.	Optimal combination (C=406μF, L=25mH): Short-circuit current 22kA, Capacitor voltage 142kV
4. Short-Circuit Inception Angle	Transient characteristics are highly influenced by phase angle; most severe overvoltage at 0°/180°; design must consider worst case.	0° phase: Short-circuit current 18kA, Capacitor voltage 201kV; 90° phase: Short-circuit current 22kA, Capacitor voltage 142kV

III. Series Resonant FCL Based on ZnO Arrester

Circuit Topology and Working Principle
• Topology Structure: The saturable reactor L_B is replaced by a ZnO arrester. The remaining structure (parallel C + series L) remains unchanged.
• Working Principle: The principle is the same as the saturable reactor type. During normal operation, the ZnO exhibits high resistance, and the circuit resonates. During a fault, the rising capacitor voltage causes the ZnO to conduct (presenting low resistance), shorting the capacitor and breaking the resonance. The series reactor L limits the current. The system recovers automatically after fault clearance. The entire process utilizes the nonlinear volt-ampere characteristics of the ZnO for automatic switching.
Current-Limiting Characteristic Simulation Analysis
Simulation under the same system conditions yielded key conclusions:

Influencing Factor	Core Conclusion	Typical Simulation Data (Example)
1. Arrester Residual Voltage & C/L Coordination	Easy to limit capacitor overvoltage, but increasing L to pursue lower short-circuit current leads to excessive voltage on the series reactor.	C=254μF, L=40mH: Short-circuit current 20kA, Reactor voltage 246kV; C=507μF, L=20mH: Short-circuit current 35kA, Reactor voltage 173kV
2. Short-Circuit Inception Angle	Transient characteristics are insensitive to short-circuit phase angle, only affecting current magnitude; maximum current at 90°.	90° phase (C=507μF, L=20mH): Short-circuit current 35kA; 0° phase: Short-circuit current 28kA

IV. Comprehensive Comparison of the Two FCL Schemes

Comparison Dimension	FCL Based on Saturable Reactor	FCL Based on ZnO Arrester
Core Advantage	Superior current-limiting effect; good balance between short-circuit current and component overvoltage achievable through parameter optimization.	Easy limitation of capacitor overvoltage; transient characteristics unaffected by short-circuit phase angle; simpler design.
Core Limitation	Requires precise optimization of core hysteresis characteristics and C/L parameters; difficult control of capacitor overvoltage; significantly affected by short-circuit phase.	Prominent overvoltage issue on the series reactor when pursuing low short-circuit current; requires strict control of L value.
Key Parameter Requirement	Optimal equivalent saturated inductance L_B2 ≈ 1/3 of the capacitive reactance.	Inductance value of the series reactor should not be too large.
Applicable Scenario Preference	Suitable for medium-low voltage levels (e.g., 110kV) in high-voltage grids, where high current-limiting performance is required.	Suitable for scenarios sensitive to capacitor overvoltage with moderate short-circuit current limiting requirements.
Common Characteristics	1. Simple structure: Composed entirely of conventional electrical components, no complex control; 2. Good economy: Cost far lower than superconducting and power electronic types; 3. High reliability: Automatic operation based on physical characteristics, no external control needed; 4. Automatic switching: Instantaneous recovery after fault clearance.

V. Conclusion

This study proposes two innovative series resonant fault current limiter solutions based on conventional components, successfully overcoming the technical and economic bottlenecks of traditional superconducting and power electronic FCLs.

Saturable Reactor FCL: Through meticulous optimization of the core hysteresis loop characteristics, setting the saturated inductance value (L_B2) to approximately 1/3 of the capacitive reactance, and ensuring good coordination with the capacitor and series reactor parameters, it can effectively suppress capacitor overvoltage and achieve excellent transient current-limiting performance. It is particularly suitable for medium-low voltage level grids such as 110kV.
ZnO Arrester FCL: Utilizing the nonlinear characteristics of ZnO easily limits capacitor overvoltage, and its performance is unaffected by the short-circuit phase angle. However, attention must be paid to avoiding overvoltage on the series reactor itself caused by excessive L values. It is more suitable for occasions with high requirements for capacitor safety and moderate current-limiting needs.

08/26/2025

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