Imagine the catastrophic consequences when a power grid system faces sudden failures like lightning strikes or equipment short circuits. If the massive instantaneous current cannot be interrupted immediately, the results could be devastating. In ultra-high voltage (UHV) AC transmission systems, circuit breakers (CBs) serve as critical "safety valves" that must react within milliseconds to ensure both system stability and human safety.
Among various types of circuit breakers, sulfur hexafluoride (SF6) breakers have emerged as the preferred choice for UHV applications. The reason lies in SF6 gas's exceptional insulation and arc-quenching properties .
In UHV environments where voltage levels are extremely high, the requirements for insulating media become exceptionally stringent. Traditional oil circuit breakers and air circuit breakers are prone to breakdown under high voltage, while vacuum circuit breakers, despite certain advantages, still face limitations in capacity and reliability for UHV applications.
SF6 gas is a synthetic inert gas with a dielectric strength 2-3 times higher than air . This means that in the same volume, SF6 gas can withstand higher voltages without breakdown, ensuring superior insulation performance. More importantly, SF6 gas exhibits outstanding arc-quenching capability.
When a circuit breaker needs to interrupt current flow, an electric arc forms between the contacts. SF6 gas rapidly absorbs the arc's energy, cooling and extinguishing it to achieve fast, reliable interruption. This rapid arc-quenching capability is critical for protecting UHV grid equipment and preventing fault escalation.
Additionally, SF6 circuit breakers offer advantages like operational stability and minimal maintenance requirements. Due to SF6 gas's chemical stability and resistance to decomposition, these breakers have long service lives and extended maintenance intervals, reducing operational costs.
However, SF6 gas does present environmental concerns as a potent greenhouse gas. Therefore, in the design and operation of SF6 circuit breakers, measures must be implemented to minimize gas leakage , while research continues into alternative gases for more environmentally friendly power systems.
With their superior insulation performance, powerful arc-quenching capability, and operational stability, SF6 circuit breakers play a pivotal role in UHV AC transmission systems as critical equipment ensuring grid safety and stability. Despite environmental challenges, through technological innovation and alternative solution exploration, SF6 circuit breakers will continue safeguarding the reliable operation of UHV power grids in the future.