In which operation mode should the generator be maintained unless notified otherwise?

Maintaining the generator in Automatic Voltage Regulation (AVR) mode is essential for effective and reliable operation of the electric power system. In this mode, the AVR automatically adjusts the generator's excitation to manage the voltage output within a predefined range. This is crucial because maintaining steady voltage levels is vital for the stability of the power grid and the protection of connected equipment.

When the generator operates in AVR mode, it provides an immediate response to fluctuations in voltage, allowing for better grid management and integration of renewable energy sources. This automatic adjustment ensures that the generator can respond to load changes and maintain stability without manual intervention, minimizing the risk of voltage drops or surges that could disrupt the power supply.

In contrast, operating in manual mode would require constant human oversight, which is not practical for continuous operations, especially during varying load conditions. The other options either do not specifically optimize the generator's performance or may not be in the best interest of system stability. Thus, maintaining the generator in AVR mode unless otherwise notified is the best practice for ensuring reliable operation within the electric power sector.