What is the most common failure mode for high-voltage SF6 circuit breakers?

The most common failure mode for high-voltage SF6 circuit breakers is that they do not close on command. This issue typically arises from various mechanical or electrical failures in the actuating mechanism. SF6 circuit breakers rely on gas pressure to operate their contacts, and if there is a failure in the pressure system or if there are issues with the drive mechanism, the breaker may fail to fully close when commanded to do so. This can lead to operational inefficiencies in power systems and may result in significant safety risks, especially in high-voltage applications.

In contrast, other failure modes listed, such as opening without command, failing to isolate, or being unable to reset, are less frequently encountered scenarios. While these can occur due to specific faults or malfunctions, they do not happen as commonly as the failure to close as commanded. The response of a circuit breaker is critical to maintaining system stability, which is why understanding these failure modes is essential for effective maintenance and operation.