High voltage circuit breaker with eco-compatible arc interruption method

A new, high voltage air-insulated switchgear (AIS) circuit breaker for substations that uses an SF₆-free and F-gas free as its insulation media, has been announced by the Pfiffner Group.

Sulphur hexafluoride, commonly known as SF₆, is a man-made gas utilised primarily as an electrical insulator and arc suppressant. While extremely effective in circuit breaker applications, it is also one of the most harmful greenhouse gases in existence. As such, component manufacturers in the electrical grid sector have been seeking solutions in recent years to limit its usage. Pfiffner ‘s solution instead uses an eco-compatible gas that eliminates the use of SF₆ and F-gases entirely.

Circuit breakers are one of the most critical components in an AIS switchyard. Reliability is crucial, as the product has to work under all conditions, and may spend many years or decades at a time dormant before being required to spring into action. When closed, the circuit breaker must behave like an ideal conductor with no resistance, and when open it must be a perfect insulator, conducting nothing. When the contacts separate upon activation, the interrupter must move instantly to extinguish any arcing and prevent damage to downstream line components. When activated this process will typically occur within 20 to 30 milliseconds, involving the high-speed movement of mechanical masses up to 20-30 kg. 

Pfiffner’s Team Lead on the development of the circuit breaker explained some of the technical challenges involved: “Arcs can get extremely hot, upwards of 25,000K, and a large concentration of gas must be forced into the area between the contacts at high speed to extinguish the arc and thus, interrupt the current. As such, components must meet stringent performance and reliability standards to ensure safety and efficacy.

“The industry has been aware of the issues of working with SF₆ for many years, however, alternatives, that can match its performance have been difficult to find. With this new circuit breaker, we believe we have found a solution that delivers on sustainability without compromising performance or safety, by means of the application of innovative concepts.”