Which of the following is typically not considered a separately derived system?

A separately derived system is one in which the source of power generation is isolated from all other sources of power, meaning it has its own grounding and bonding arrangement.

In the context of the options, an autotransformer typically shares a common connection between its primary and secondary windings, which means that it does not completely isolate its secondary side. If the autotransformer has a grounded conductor, it can be connected to the same grounding system as the source, potentially allowing fault currents to flow back, indicating it lacks the separate derivation aspect. This characteristic makes it distinct from the other systems listed, which maintain their own grounding methods independent of other sources.

Generators, transformers, and solar power systems generally provide isolated circuits, as they are individually grounded and meant to operate independently regarding safety and fault protection.