What likely caused a local transmission line to trip after making contact with a tree, resulting in all breakers on the bus standing open?

The situation described involves a local transmission line that tripped upon contact with a tree, leading to all breakers on the bus standing open. The breaker failure relay is designed to detect when a breaker has tripped but fails to clear a fault or disconnect the faulted section of the system. When the line made contact with a tree, it likely created a fault condition that caused the circuit breaker to trip in response.

In this scenario, if the breaker tripped but then failed to operate correctly, the breaker failure relay would activate. Its primary function is to ensure that the system operates safely by taking necessary actions, such as signaling other components to open or trip, which would explain why all breakers on the bus stand open.

Other options, while related to protection schemes, do not directly address the condition of a trip followed by failure to clear the fault, leading to all breakers being open. For instance, a differential relay monitors the difference in current, while a ground relay focuses specifically on ground faults, and an SPS/RAS (Special Protection Scheme/Remedial Action Scheme) is used for broader operational strategies rather than immediate breaker failure response. Ultimately, the breaker failure relay is the most fitting explanation for the behavior observed in this situation.