What might cause an alarm on SCADA indicating a bus breaker is closed while the bus appears de-energized?

The correct choice is associated with breaker failure, which can lead to an alarm indicating that a bus breaker is closed even though the bus itself is de-energized. In the context of SCADA systems, a bus breaker is designed to connect or disconnect electrical circuits. If there is a failure within the breaker itself and it does not operate as intended, the system may still indicate that the breaker is closed due to a malfunction, even when the bus is not energized.

This situation could arise from the primary relay failing to detect a fault and thus not opening the breaker, while the backup relay may take action based on the faulty conditions, leading to conflicting indications on the SCADA. The alarm system in SCADA relies on inputs from multiple devices, and a failure of the breaker without appropriate detection can cause this discrepancy.

Other choices could lead to similar alarms but do not accurately address the complexities involved in a closed breaker indication while the bus remains de-energized. For example, a loss of power to the RTU might result in a complete lack of communication or false alarms, while auto reclosing would imply that the breaker is attempting to operate correctly. A failure of the RTU, like the loss of power, would hinder reliable operation and proper indication