8 Types of Load Break Switch You Should Know

Load break switches (LBS) play a vital role in electrical distribution systems by safely interrupting and isolating electrical circuits under load conditions. Unlike standard switches, load break switches are designed to handle current interruption without causing damage or safety hazards. Understanding the different types of load break switch available is essential for engineers, technicians, and decision-makers who work with power systems across various voltage levels and applications.

In this article, we will explore 8 key types of load break switches. We will categorize them by their arc interruption medium and voltage ratings to help you choose the right switchgear component for your needs.

5 Types of Load Break Switch by Arc Interruption

Load break switches are often classified by the technology they use to extinguish the electric arc generated when breaking a circuit under load. Here are 5 common types:

Air Break Switches

Air break switches use ambient air as the arc extinguishing medium. When the contacts open, the arc forms in the air and is quenched by separating the contacts and increasing the arc length. These switches are typically used in outdoor substations and overhead distribution lines due to their simplicity and reliability.

Advantages:

• Simple construction
• Cost-effective
• Suitable for medium voltage applications

Limitations:

• Larger physical size due to arc length requirements
• Less suitable for high voltage systems

Oil Break Switches

Oil break switches extinguish the arc by submerging it in insulating oil. The oil cools and breaks down the arc quickly. These switches are widely used in indoor substations and transformer installations.

Advantages:

• Efficient arc quenching
• Compact compared to air break switches

Limitations:

• Requires regular oil maintenance
• Environmental concerns due to oil leakage risks

Vacuum Breaker Switch

A vacuum breaker switch uses a vacuum to extinguish the arc. The absence of gas or air molecules prevents arc formation when the contacts open. Vacuum load break switches are popular in medium and high voltage systems because of their fast operation and low maintenance.

Advantages:

• High dielectric strength
• Long service life
• Environmentally friendly (no oil or gas)

Limitations:

• Higher initial cost
• Requires precise manufacturing

SF6 Load Break Switch

SF6 load break switches utilize sulfur hexafluoride (SF6) gas as the arc extinguishing and insulating medium. SF6 has excellent dielectric properties, making these switches ideal for high voltage and compact installations such as high voltage substations.

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Advantages:

• Superior arc quenching capabilities
• Compact size
• High reliability and safety

Limitations:

• SF6 is a potent greenhouse gas, requiring careful handling
• Higher costs and regulatory requirements

Solid Dielectric Load Break Switches

These switches use solid insulating materials, such as epoxy resin, for arc extinction and insulation. Solid dielectric load break switches are compact, environmentally friendly, and require minimal maintenance, making them suitable for modern medium voltage distribution systems.

Advantages:

• Compact and lightweight
• No gas or oil, environmentally safe
• Low maintenance requirements

Limitations:

• Typically used for medium voltage levels
• Limited arc interruption capacity compared to gas-based switches

3 Types of Load Break Switch by Voltage

Another way to categorize load break switches is based on the voltage level they are designed to handle. Here are the three main voltage classes:

Medium Voltage Load Break Switch

Medium voltage load break switches operate typically between 3 kV and 36 kV. They come in various designs including metal-enclosed indoor, metal-enclosed outdoor, and outdoor non-enclosed types. Their interruption methods may include SF6 gas, vacuum, or oil.

These switches are widely used in distribution networks and substations, providing reliable circuit isolation and fault current interruption capabilities.

High Voltage Load Break Switch

High voltage load break switches are designed for voltages above 36 kV and can be further classified by their arc quenching methods:

• Solid gas-producing high pressure switches that generate gas from arc energy to extinguish the arc.
• High pressure air blast switches that use compressed air to blow out the arc.
• Oil immersed load break switches that rely on oil gasification and cooling to interrupt current.

They are often found in high voltage transmission systems and large substations requiring robust switching devices.

Low Voltage Load Break Switch

Low voltage load break switches are typically rated for voltages up to 1 kV. They combine components such as miniature circuit breakers (MCB), molded case circuit breakers (MCCB), and isolators with HRC fuses. They are commonly used in residential, commercial, and light industrial electrical systems to protect and isolate circuits.

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Conclusion

Understanding the types of load break switch and their specific arc interruption technologies and voltage ratings is crucial for selecting the right switchgear component in power distribution systems. Whether it’s an air break switch for outdoor overhead lines, a vacuum breaker switch for modern substations, or an SF6 load break switch for compact high voltage applications, each type offers unique advantages suited to different operational and environmental requirements.

By choosing the appropriate load break switch, electrical engineers and facility managers can ensure safe, reliable, and efficient operation of their power networks.