Technological Innovation

What is the rating of 66 kV vacuum breaker?

The rating of a 66 kV vacuum breaker refers to its specified voltage capability and current interruption capacity. This technical article aims to provide an in-depth understanding of the rating system for vacuum breakers at this voltage level.

Ratings System for Vacuum Breakers

Vacuum breakers, also known as circuit breakers, play a crucial role in electrical power systems by interrupting fault currents and protecting equipment from damage. The rating of a vacuum breaker is determined by several factors:

Voltage Rating: The voltage rating represents the maximum voltage that the breaker can safely handle. In the case of a 66 kV vacuum breaker, it is designed specifically for a system voltage of 66,000 volts.

Interrupting Capacity: Also known as breaking capacity, it indicates the maximum amount of current the breaker can interrupt under specified test conditions. A higher interrupting capacity ensures the breaker can safely interrupt fault currents without damaging itself.

Short-Time Current Rating: This rating specifies the maximum current the breaker can carry for a short duration, typically a few seconds, without tripping or sustaining damage. It is essential for applications where high inrush currents occur during system faults.

Continuous Current Rating: It defines the maximum current that the breaker can continuously carry without exceeding its temperature limits. This rating is crucial for establishing the breaker's long-term reliability.

66 kV Vacuum Breaker Rating Considerations

When selecting or designing a 66 kV vacuum breaker, engineers must consider various technical factors to ensure its performance and reliability:

1. Dielectric Strength:

The insulation material used in the breaker must have sufficient dielectric strength to withstand the voltage stress at 66 kV. This ensures reliable operation and prevents electrical breakdown.

2. Mechanical Endurance:

The vacuum interrupter contacts undergo mechanical stress during the opening and closing operations. The breaker design should account for the number of operations it can sustain without degradation or failure.

3. Temperature Rise:

Due to the continuous current flowing through the breaker, heat is generated. The design should consider cooling mechanisms to keep the temperature rise within acceptable limits.

4. Environmental Considerations:

Factors such as humidity, pollution, and altitude can affect the performance of a vacuum breaker. Design and testing should account for the specific environmental conditions where the breaker will be installed.


The rating of a 66 kV vacuum breaker encompasses its voltage capability, current interruption capacity, and other key considerations. Engineers carefully select and design breakers to ensure optimal performance and protection in electrical power systems operating at this voltage level. Understanding the rating system helps in making informed decisions and maintaining the reliability of the power network.


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