LW8-40.5 outdoor three-phase Sulfur Hexafluoride (SF6) Circuit Breaker

1. Core Structure and Working Principle

1.1 Overall Structure

This circuit breaker typically features a three-phase split porcelain column type or floor-mounted tank type structure, with three-phase arc-extinguishing chambers assembled separately and connected by copper pipes to ensure balanced air pressure across the three phases. Core components include post insulators, pressure-blast arc-extinguishing chambers, adsorbers, current transformers, transmission boxes, and underframes. The porcelain sleeves serve both as support and insulation, offering high strength and excellent airtightness; the adsorbers are equipped with F-03 molecular sieves to adsorb moisture in SF₆ gas and low fluorides generated by arc decomposition.

1.2 Operation and Arc Extinguishing

It comes standard with a CT14-type spring operating mechanism, enabling three-phase linked operation with an energy storage time of ≤15s and a mechanical life of over 3,000 operations (some models can even reach 5,000 operations). The arc-extinguishing chamber adopts a single-pressure pressure-blast design: during opening, the movable cylinder and contact seat move relative to each other to compress SF₆ gas, and the high-pressure gas blows the arc through the nozzle, extinguishing it when the current passes through zero—achieving high arc-extinguishing efficiency and short arcing time. Additionally, it is equipped with a new MKZ-type SF₆ pointer density gauge, whose readings are not affected by temperature, facilitating real-time monitoring of gas pressure.

2. Key Technical Parameters

Parameter Name	Specific Values
Rated Voltage	40.5kV
Rated Current	1600A/2000A/2500A (and other specifications)
Rated Short-Circuit Breaking Current	20kA, 25kA, 31.5kA (and other specifications)
Rated SF₆ Gas Charging Pressure (Gauge Pressure at 20℃)	0.4 - 0.5MPa
Opening Time	≤60ms
Closing Time	≤100ms
Rated Current for Making and Breaking a Single Capacitor Bank	400A
Annual Gas Leakage Rate	≤1%
Overall Weight (Including Operating Mechanism)	Approximately 1000 - 1400kg

3. Core Performance Advantages

• Strong Electrical Life and Operational Stability: At rated voltage, it can continuously break the rated short-circuit current 16 - 21 times without maintenance or SF₆ gas replacement; it can switch off 50km of unloaded long lines and make/break 400A capacitor banks without restriking, suitable for frequent operation scenarios.

• Flexible Adaptability: Each unit can be equipped with up to 12 current transformers. Some transformers use high-permeability microcrystalline alloy materials with an accuracy of Class 0.2 or 0.2S, meeting diverse measurement and protection needs, and the wiring mode of transformers can be flexibly adjusted.

• Comprehensive Compliance: The product complies with the requirements of the national standard GB1984 - 89 AC High-Voltage Circuit Breakers and the International Electrotechnical Commission (IEC) standard IEC56 (or IEC60056), aligning with universal industry norms for electrical equipment.

4. Applicable Environment and Scenarios

4.1 Environmental Conditions

Under normal operating conditions, it can withstand an ambient temperature range of -30℃ to +40℃ (special customized models can reach as low as -40℃); the conventional altitude adaptability is ≤2500m (plateau-type models can adapt to 4000m environments); it can withstand wind speeds of ≤35m/s and a maximum seismic intensity of Grade 8, suitable for environments with pollution grades Ⅱ - Ⅳ, adapting to most complex outdoor climates.

4.2 Application Scenarios

It is mainly used in 40.5kV (corresponding to 35kV systems) power transmission and distribution systems to undertake control and protection tasks for electrical equipment, and can also be used as an interconnection circuit breaker. It is commonly found in urban distribution networks, industrial and mining distribution systems, and is also suitable for special working conditions such as switching capacitor banks.