What defines a separately derived system?

A separately derived system is defined as a system powered by its own source with no direct electrical connection to the supply conductors of any other system. This means that the system operates independently and does not share a physical connection with other electrical systems, thereby ensuring that its grounding and bonding can be managed separately.

The significance of this definition lies in the way grounding and bonding are handled. In a separately derived system, the grounding electrode system is isolated from other systems, which can provide enhanced protection against certain types of faults and ensure that the grounding path is designed specifically for that particular source.

The other options pertain to different characteristics of electrical systems. A directly connected system would imply a shared connection, which does not fit the definition of a separately derived system. A solidly connected grounded circuit conductor relates to how grounding is implemented but does not capture the essence of independence found in separately derived systems. While transformers can be utilized in various systems, including separately derived systems for voltage reduction, their presence alone does not define the system as separately derived; the independence of the power source is the crucial factor.