What is the condition for a generator circuit to maintain operation?

For a generator circuit to maintain operation, it is crucial that the generator itself is functioning effectively. A surviving generator implies that it is operational and capable of producing electricity. This includes having all necessary components, such as the rotor, stator, and excitation system, in good working condition. If the generator is not operational for any reason, including mechanical failure or damage, it cannot generate electricity, effectively halting its operation.

The other options, while related to the overall functioning of power generation systems, do not directly address the fundamental requirement of having a working generator. Sufficient water supply could apply to hydroelectric generators, maintaining steady voltage supply is essential but dependent on the generator's operation, and optimal fuel levels are more relevant to fossil fuel generators rather than the circuit itself. Therefore, the operational status of the generator is the primary condition needed to ensure the circuit continues to function.