Ultra-Fast Current Limiter (FCL): Isang Revolutionary na Solusyon na May Millisecond-Level na Interruption ug Economic Benefits

Overview: Redefining Speed and Economics in Short-Circuit Protection

Ania nga solusyon nagfokus sa usa ka ultra-fast short-circuit current limiting device, gihimo aron matubag ang kasagaran nga problema sa pagdako sa short-circuit currents ug matiyak ang kalambigitan sa power grids ug equipment.

1.1 Core Features

Ultra-Fast Interruption Speed: Nag-detekta og sayop ug nagsugyot sa current sa loob sa 1 milisegundo, efektibo nga natigom ang short-circuit current bago maabot ang iyang peak.
High Interruption Capacity:

Suitable para sa 12kV/17.5kV systems: Maximum breaking capacity nga 210kA (RMS).
Applicable para sa 24kV/36kV/40.5kV systems: Maximum breaking capacity nga 140kA (RMS).

1.2 Core Advantages

Economic Efficiency: Nagoperate sa parallel uban sa current-limiting reactors aron mapasabot ang pinaka cost-effective nga limiting solution. Naausab ang pagpuli sa entire switchgear panels o transformers tungod sa pagdako sa short-circuit currents, makapahinayog sa investment sa bag-ong o upgraded substations.
Broad Compatibility: Ideal para sa interconnecting switchgear ug substations; sa daghang mga scenario (e.g., parallel operation of multiple transformers), kini ang tuman-ang teknikal nga solusyon.
Exceptional Reliability:

Hinatagan og higit pa sa 60 ka tuig nga global operational experience (gin-invent niadtong 1955), ginpatunay sa liboan ka proyekto sa buhatan sa mundo.
Ang estadistika gikan sa halos 4,000 ka yunit nagpakita og average operation frequency nga raka una sa pipila ka tuig, nagpakita sa stable ug reliable nga performance.

Key Technical Q&A

No.	Key Question	Core Answer
1	Unsa ang peak short-circuit current?	Ang maximum instantaneous value human sa unang cycle human sa short-circuit fault, resulta sa superposition sa periodic ug non-periodic components. Igihiusa kini og dako nga electromagnetic forces (testing dynamic stability) ug heat (testing thermal stability).
2	Bakit limitahan ang peak short-circuit current?	Ang peak currents nga mas taas sa rated withstand parameters sa equipment mahimong moguba sa switchgear, circuit breakers, current transformers, ug cable connectors pinaagi sa dako nga electromagnetic forces.
3	Pamuno kung unsaon pag-adapt sa parallel operation of multiple transformers?	Para sa switchgear nga may withstand capability nga 2Ik, sa usa ka system nga adunay apat ka transformers (4Ik) sa parallel, makaya ang perfect adaptation pinaagi sa pag-install og fast current limiters sa gitas nga bus sections (e.g., sa pagitan sa sections 1-2 ug 3-4).
4	Unsa ang tripping criteria? Unsaon pag-iwas sa false trips?	Ang control unit nag-monitor sa instantaneous current (I) ug rate of current rise (di/dt). Ang trip mag-trigger lang kung parehas sila mag-exceed sa set thresholds. Kini nga dual criterion siguro nga ang tikang nga short-circuit currents lang ang gi-interrupt, ang general faults gibahin sa downstream circuit breakers.
5	Unsaon ang maintenance human sa operation?	Ang core operating component (conductive bridge) may modular design ug mahimong ibalik sa repair. Ang kinahanglan ra i-replace mao ang internal conductive core, inductive filler, ug parallel fuses; ang uban pang mga komponent reusable, makapahinayog sa kaayo ka gamay nga maintenance costs.

Core Functions and Value

3.1 Core Function

Nag-detekta ug nagsugyot sa sayop sa initial rising stage of short-circuit current (within 1ms), efektibo nga natigom ang damage sa power equipment tungod sa insufficient dynamic ug thermal stability. Perfectly nag-compensate sa inherent limitations sa traditional circuit breakers—"slow to act and unable to suppress the first half-wave peak current."

3.2 Comparative Advantages

Comparison Object	Advantage Details
Traditional Circuit Breakers	Ang breakers mag-operate sa tens of milliseconds aron interrupt, dili makaputli sa impact sa unang peak current. Kini nga limiter nag-responde sa 1ms, nagsugyot sa actual peak short-circuit current sa mas gamay nga level.
Current-Limiting Reactors	Nag-iwas sa voltage drop, active losses (copper losses), ug reactive losses associated sa reactors sa continuous operation. Ug nag-iwas usab sa generator regulation issues resulta sa integration sa reactor.

3.3 Applicable Scenarios

Power plants
Large industrial grid substations
Specific key circuits/scenarios: Transformer/generator feeder circuits, bus tie sections, reactor bypass applications, ug interconnection points between grids ug captive power sources.

Structure and Design

4.1 Overall Composition

Ang three-phase AC system fast current limiter gisangpot sa:

3 conductive bridge bases
3 conductive bridges
3 matching current transformers
1 control unit

4.2 Key Component Details

Component Name	Composition / Features	Key Parameters / Rules
Conductive Bridge Base	Includes mounting plate, insulators, pulse transformer, ug connectors with quick couplings	- Rated current ≥2500A ug voltage 12/17.5kV: Bolted connections. - Pulse transformer: ≤17.5kV (installed only at the bottom); ≥24kV (installed at both top ug bottom for reliable isolation).
Conductive Bridge	Conductive core ug inductive filler encapsulated in an insulating cover	Upon tripping, ang inductive filler mag-trigger, driving the conductive core to break rapidly at its pre-cut; current then transfers to the parallel fuse.
Matching Current Transformer	Bushing or block type, series-connected in the main circuit	Features a gapped core (high overcurrent factor, low remanence) ug shielded primary/secondary windings (low impedance) to ensure measurement accuracy ug speed.
Control Unit	Includes power supply, control, indication, ug anti-interference units	- Dimensions: 600mm (W) × 1450mm (H) × 300mm (D); weight: 100kg. - Indication unit: 5 flag relays (3-phase trip indication + readiness monitoring + power supply monitoring).

Working Principle: Achieving 1ms Current Limiting

5.1 Core Composition

Ang device essentially an intelligent parallel combination of two components:

"Extremely fast switch (conductive bridge)": Carries rated current during normal operation ug opens instantaneously during faults.
"High-breaking-capacity fuse": Ultimately interrupts the high current after the switch opens.

5.2 Operation Sequence

Detection: Matching current transformers (CTs) continuously collect current signals; ang control unit calculates instantaneous current (I) ug rate of current rise (di/dt).
Judgment: When both I ug di/dt exceed set values, ang control unit immediately issues a trip command (independent three-phase judgment ug triggering).
Interruption: The trip capacitor discharges into the pulse transformer, triggering the inductive filler in the conductive bridge. This generates high-pressure gas, causing the conductive core to rupture at its pre-cut within 1ms.
Current Limiting: Arc resistance increases rapidly, transferring current to the parallel fuse. The fuse begins limiting within 0.5ms ug extinguishes the arc completely at the next current zero, clearing the fault.

5.3 Auxiliary Units

Power Unit: Provides 150V DC power to charge the trip capacitor ug supply electronic components. Includes a watchdog circuit to monitor system health.
Anti-Interference Unit: All external wiring passes through this unit, providing effective protection against external electromagnetic interference ug preventing false operations.

Commissioning and Testing

6.1 Testing Requirements

Regular functional testing is required, which can be executed by users or ABB service engineers.

6.2 Dedicated Equipment

Simulator: Temporarily replaces the conductive bridge during testing. Its built-in neon lamp lights up upon receiving a trip pulse, indicating proper operation.
Test Plug & Test Instrument: Used to check trip output voltage ug overall functionality. Features a user-friendly interface ug easy operation (dimensions: 400×215×320mm; weight: 11kg).

Scope of Supply and Parameters

7.1 Supply Models

Model Type	Applicable Scenarios	Core Configuration
Discrete Components	For installation in existing switchgear	3 bases + 3 conductive bridges + 3 CTs + 1 control unit
Drawout Cabinet	For metal-clad switchgear	Conductive bridges mounted on withdrawable carts (with isolating switch function); CTs fixed; control unit installed in the low-voltage compartment
Fixed Cabinet	- For 12/17.5/24kV systems - Mandatory for 36/40.5kV systems	All components fixed inside the cabinet. For 36/40.5kV systems, the control unit is often installed in a separate control box.

7.2 Key Technical Parameters (Example: Discrete Components)

Note: ¹ indicates forced air cooling is required; compatible with 50/60Hz frequency.

Technical Parameter	Unit	12kV	17.5kV	24kV	36/40.5kV
Rated Voltage	V	12000	17500	24000	36000/40500
Rated Current	A	1250-5000¹	1250-4000¹	2500-4000¹	1250-3000¹
Rated Short-Circuit Breaking Current (Max.)	kA RMS	210	210	210	140

Typical Application Scenarios

Application Scenario	Core Issue	Solution Value
Parallel System Operation	Short-circuit current from multiple transformers in parallel exceeds switchgear ratings	1. Allows reduced system impedance, minimizing voltage drop. 2. Optimizes transformer load distribution, reducing losses. 3. Enables uninterrupted load transfer during faults, improving supply reliability.
Grid-Captive Power Interconnection	Captive generator operation causes excessive short-circuit current at the common coupling point	The only rational solution. Can be equipped with directional tripping (requires CT at generator neutral) to ensure operation only for grid-side faults.
Bypassing Current-Limiting Reactors	Reactors in continuous operation cause losses ug voltage drop	Bypasses reactors during normal operation (zero loss, zero voltage drop); rapidly interrupts during short circuits, diverting current to the reactor for limiting.
Selective Application of Multiple Units	Selective operation required when multiple limiters are installed on multi-section buses	Uses "current vector sum" criterion to ensure only the limiter closest to the fault operates. Supports up to 5 transformers in parallel (using 4 limiters).