Basic Knowledge of High Voltage Circuit Breakers - Definition, Classification and Working Principles Explained in Detail

High voltage circuit breakers are indispensable core protective devices in power systems, widely used in power plants, substations, industrial and mining enterprises, and distribution networks. Their main functions are: to connect or disconnect load current during normal operation; and in the event of short circuits, overloads and other faults, to receive instructions from relay protection devices and quickly interrupt fault currents, preventing accident expansion and ensuring the safety of the power system and equipment.

Classification of High Voltage Circuit Breakers

Based on the different arc extinguishing media, high voltage circuit breakers are mainly classified into the following types:

Oil Circuit Breakers: Use insulating oil as the arc extinguishing and insulating medium, widely used in the early days, but gradually being phased out due to large size, inconvenient maintenance, and fire hazards.

Compressed Air Circuit Breakers: Use high-pressure compressed air for arc extinguishing, with strong interrupting capability, but complex structure and many auxiliary devices, now basically out of the market.

Sulfur Hexafluoride (SF6) Circuit Breakers: Use SF6 gas as the arc extinguishing and insulating medium, with excellent arc extinguishing performance and insulation strength, currently the mainstream product for 110kV and above voltage levels.

Vacuum Circuit Breakers: Use high vacuum as the arc extinguishing medium, with simple structure, small size, convenient maintenance, environmentally friendly and pollution-free, dominating the medium voltage field at 35kV and below.

Solid Gas-generating Circuit Breakers: Use solid gas-generating materials to produce gas for arc blowing under the high temperature of the arc, mainly used for lower voltage levels.

Working Principle of High Voltage Circuit Breakers

Closing Process: The operating mechanism releases energy, driving the moving contact through the transmission mechanism to move at high speed and make contact with the fixed contact, completing circuit connection.

Opening Process: Upon receiving the opening command, the operating mechanism releases the holding force, and the contacts separate rapidly under the action of the opening spring. The moment the contacts separate, an arc is generated, and the arc extinguishing device promptly intervenes, extinguishing the arc through elongation, cooling, splitting and other methods.

The Status of High Voltage Circuit Breakers in the Power System

As the foremost of the three major switchgear in power systems, the reliability of high voltage circuit breakers directly affects grid safety. Statistics show that circuit breaker failures are an important cause of complete substation outages. Therefore, understanding their working principles and mastering correct selection and maintenance methods are of vital importance to every power industry practitioner.