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

Overview

Features

Structural Configuration

The LW8-40.5 SF6 circuit breaker is available in a three-phase independent porcelain post configuration or a floor-mounted tank structure, depending on application requirements. Each phase is equipped with a separate arc-extinguishing chamber, and the three-phase SF6 gas systems are interconnected through copper pipes to maintain uniform gas pressure and stable insulation performance.

The main components include porcelain support insulators, pressure-blast arc-extinguishing chambers, SF6 gas adsorbers, current transformers (CT), transmission mechanisms, and supporting frames.

The porcelain insulators provide both mechanical support and electrical insulation, featuring high mechanical strength and excellent sealing performance. The built-in F-03 molecular sieve adsorber effectively removes moisture and low-fluoride decomposition products generated during arc interruption, helping maintain SF6 gas quality and ensuring long-term insulation reliability.

Operating Mechanism and Arc Extinguishing Principle

The LW8-40.5 is equipped with a reliable CT14-type spring operating mechanism, enabling synchronized three-phase operation. The energy storage time is ≤15s, and the mechanical endurance exceeds 3,000 operations, with certain models capable of reaching up to 5,000 operations.

The arc-extinguishing chamber adopts a single-pressure puffer-type design. During the opening process, the relative movement between the moving cylinder and contact assembly compresses the SF6 gas, generating a high-pressure airflow. The gas flow is then directed through the nozzle to rapidly cool and extinguish the arc when the current reaches zero crossing.

This optimized arc-extinguishing system provides high interruption efficiency, short arcing duration, and reliable fault-clearing performance.

For convenient operation and maintenance, the circuit breaker is equipped with an MKZ-type SF6 pointer density monitor. The display accuracy is not significantly affected by temperature variations, allowing operators to monitor SF6 gas pressure conditions in real time and ensure safe operating status.

Technical Data

Overall and mounting dimensions(mm)

Key Performance Advantages

Excellent Electrical Endurance and Operational Reliability

The LW8-40.5 SF6 circuit breaker provides outstanding electrical endurance under rated operating conditions. It is capable of continuously interrupting rated short-circuit currents for 16–21 times without maintenance or SF6 gas replacement, ensuring reliable operation throughout its service life.

The circuit breaker is also suitable for demanding switching applications, including interruption of unloaded transmission lines up to 50km and reliable switching of 400A capacitor banks without restriking. These characteristics make it suitable for power systems requiring frequent switching operations and high operational stability.

Flexible Current Transformer Configuration

The LW8-40.5 supports flexible current transformer (CT) configurations, with each unit capable of integrating up to 12 current transformers according to protection and measurement requirements.

Some CT configurations utilize high-permeability microcrystalline alloy materials, achieving accuracy classes of 0.2 or 0.2S. The transformer arrangement and wiring configuration can be customized to meet different monitoring, protection, and measurement requirements.

Compliance with International and Industry Standards

The LW8-40.5 SF6 circuit breaker is designed in accordance with the requirements of the Chinese national standard GB1984-89 AC High-Voltage Circuit Breakers and the international standard IEC56 (IEC60056) High-Voltage AC Circuit Breakers.

Its design, manufacturing, and testing procedures comply with widely accepted industry specifications, ensuring reliable electrical performance, mechanical durability, and compatibility with standard 40.5kV power systems.

Operating Environment and Application Areas

Environmental Adaptability

The LW8-40.5 SF6 circuit breaker is designed for reliable outdoor operation under various environmental conditions. The standard configuration supports an ambient temperature range from -30℃ to +40℃, while specially customized versions can operate at temperatures as low as -40℃.

The standard model is suitable for installation at altitudes up to 2,500m, with high-altitude versions available for applications up to 4,000m. The equipment can withstand wind speeds of ≤35m/s and seismic intensity up to Grade 8.

With enhanced insulation design, the circuit breaker can operate reliably in environments with pollution levels Class II to Class IV, making it suitable for a wide range of outdoor installation conditions.

Typical Applications

The LW8-40.5 SF6 circuit breaker is mainly applied in 40.5kV power transmission and distribution systems (corresponding to 35kV voltage classes), providing reliable control, switching, and protection for electrical equipment.

It can also serve as an interconnection circuit breaker in power networks. Typical applications include urban distribution systems, industrial and mining power networks, substations, and installations requiring reliable capacitor bank switching capability.