Which component disconnects a generator if it exceeds the maximum voltage threshold?

The Generator Control Unit (GCU) plays a vital role in managing the performance of the aircraft's generator system. One of its key functions is to monitor the generated voltage and ensure it remains within predefined limits. If the output voltage from the generator exceeds the maximum voltage threshold, the GCU will automatically disconnect the generator to prevent damage to the electrical system and connected components. This protective action helps maintain the overall integrity and safety of the aircraft's electrical systems.

While other options may involve power management or control in some way, they do not directly serve the specific function of monitoring and disconnecting the generator based on voltage exceedance. The battery switch is primarily used for connecting or disconnecting the battery circuit; the APU GCU relates to the auxiliary power unit's generator; and the voltage regulator regulates voltage but does not disconnect the generator itself. Therefore, the function of monitoring voltage thresholds and disconnecting the generator is specifically the responsibility of the Generator Control Unit.