The working principle of a high-voltage load break switch (HV LBS) is similar to that of a circuit breaker, featuring a simple arc-extinguishing device. However, its design is relatively straightforward.

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Operating Mechanism of the High-Voltage Load Break Switch

1. Opening Operation:
   When the switch opens, the opening spring activates, causing the main shaft to rotate clockwise. This triggers two key processes:

   • Gas Compression: A crank-slider mechanism moves the piston upward, compressing the gas.
   • Contact Separation: Through a transmission system comprising two sets of four-bar linkage mechanisms, the main blade opens first. Then, the arc-extinguishing blade opens the arc contact, and the compressed air from the cylinder extinguishes the arc through a nozzle.
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2. Closing Operation:
   During closing, the main blade and arc-extinguishing blade rotate clockwise simultaneously via the main shaft and transmission system:
    

   • Arc Contact Closing: The arc contact closes first.
   • Main Contact Closing: As the main shaft continues to rotate, the main contact closes afterward.
     During this process, the opening spring stores energy for the next operation.

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Key Features and Application

Since the high-voltage load break switch cannot interrupt short-circuit currents, it is typically used alongside a current-limiting high-voltage fuse. The load switch handles the switching of load currents, while the fuse provides short-circuit protection. This combination ensures effective circuit interruption and significantly reduces the thermal and electrical effects of short-circuit currents.

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Common Models and Ratings

Examples include 12kV, 24kV, and 36kV load break switches such as FN7-12, FN7-24, FN18, and NAL12.