Comprehensive Comparison: Load Break Switch (LBS) vs. Circuit Breaker (CB)
In high-voltage power transmission and distribution systems, both Load Break Switches (LBS) and Circuit Breakers (CB) function as switching devices. However, they have significant differences in structure, functionality, application scenarios, and protection capabilities.
1. Load Break Switch (LBS)
1.1 Definition & Function
A Load Break Switch (LBS) is a device that can switch electrical circuits under load conditions but cannot interrupt short-circuit currents. It is mainly used to break normal operating currents and is often paired with high-voltage fuses for short-circuit protection.
1.2 Key Features
✅ Can break load current but cannot interrupt short-circuit current
✅ No built-in protection function, requires fuse assistance
✅ Simple structure, low maintenance, cost-effective
✅ Used in ring main units (RMU) and branch circuits
✅ Typically applied in medium voltage (3.6kV~40.5kV) systems
1.3 Common Types of LBS
| Type | Operating Principle | Voltage Rating | Application |
|---|---|---|---|
| Air Load Break Switch (Air LBS) | Uses air for insulation and arc extinction | 3.6kV-12kV | Low-voltage distribution, substation feeders |
| SF₆ Load Break Switch (SF₆ LBS) | Uses SF₆ gas for insulation and arc extinction, excellent breaking capability | 12kV-24kV | RMUs, urban distribution networks |
| Vacuum Load Break Switch (Vacuum LBS) | Uses vacuum interrupters, SF₆-free, environmentally friendly | 12kV-40.5kV | Indoor distribution, industrial applications |
1.4 Application Scenarios
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Urban distribution networks (Ring Main Units – RMU): Used in branch circuits or transformer feeders
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Industrial power distribution: Suitable for stable loads without short-circuit protection needs
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Renewable energy applications: Used in solar power collector boxes, wind farm substations, and similar scenarios
2. Circuit Breaker (CB)
2.1 Definition & Function
A Circuit Breaker (CB) is a device that can interrupt both load current and short-circuit current, providing overload, short-circuit, and undervoltage protection. It plays a critical role in power system protection, preventing damage to electrical grids and equipment.
2.2 Key Features
✅ Capable of breaking short-circuit currents, providing system protection
✅ Built-in short-circuit, overload, and undervoltage protection
✅ Suitable for high-current applications and critical circuit protection
✅ Used in industrial, substation, and transmission networks
✅ Higher maintenance requirements and costs compared to LBS
2.3 Types of Circuit Breakers
| Type | Arc Extinction Method | Voltage Rating | Application |
|---|---|---|---|
| Vacuum Circuit Breaker (VCB) | Uses vacuum interrupters, eco-friendly and low maintenance | 12kV-40.5kV | Industrial power distribution, substations, switching stations |
| SF₆ Circuit Breaker (SF₆ CB) | Uses SF₆ gas for insulation and arc extinction, ideal for high voltage | 40.5kV-550kV | Transmission lines, large substations |
| Air Circuit Breaker (ACB) | Uses air arc extinction, mainly for low-voltage applications | <1kV | Low-voltage distribution panels |
2.4 Application Scenarios
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Substations and power grids: Main protection equipment for high-voltage substations, ensuring grid stability
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Industrial power protection: Large-scale industrial distribution systems, preventing overload and short circuits
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Railway and renewable energy applications: Used in railway power supply systems, wind farms, and solar power stations
3. Comparison: Load Break Switch (LBS) vs. Circuit Breaker (CB)
| Criteria | Load Break Switch (LBS) | Circuit Breaker (CB) |
|---|---|---|
| Function | Breaks load current, no short-circuit protection | Provides short-circuit, overload protection, and can interrupt fault currents |
| Short-Circuit Interruption | ❌ No | ✅ Yes |
| Automatic Protection | ❌ Requires fuse for protection | ✅ Built-in short-circuit, overload protection |
| Maintenance | Low, minimal operational cost | Requires periodic maintenance |
| Current Capacity | ≤630A (typically) | Can handle thousands of amperes |
| Application | 10kV-24kV RMUs, branch circuits | 10kV-110kV primary power distribution |
| Cost | Lower | Higher |
4. Selection Guide
✅ When to Choose a Load Break Switch (LBS)?
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When only load current switching is required, without short-circuit protection
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Suitable for RMUs, branch circuits, transformer feeders
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Systems that already have fuse protection, allowing LBS to act as a switching device
✅ When to Choose a Circuit Breaker (CB)?
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When short-circuit and overload protection are required
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Ideal for industrial loads, main power distribution systems
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Suitable for remote monitoring and automated protection systems
5. Conclusion
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Load Break Switches (LBS) are used for medium-voltage distribution system branch circuits, cannot break short-circuit currents, and are often used alongside fuses.
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Circuit Breakers (CB) are used for main distribution circuits, capable of short-circuit and overload protection, making them suitable for substations, industrial applications, and transmission systems.
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If short-circuit protection is required, CB is the preferred choice, while LBS is better for basic load switching.