Which type of grounding system is isolated from the main electrical system?

A separately derived system is distinct because it operates with its own grounding setup that does not connect back to the primary electrical system. This means that any faults or issues in the separately derived system do not directly impact the primary system, which provides a measure of safety and isolation. This type of grounding is often used in specialized electrical installations, such as those in hospitals or in certain industrial applications where equipment needs to be isolated for operational safety or for reducing the risk of electrical shock.

In contrast, a solidly grounded system connects directly to the earth without impedance, providing a low-resistance path for fault current. A low-resistance grounding system similarly provides a path but is designed for specific applications to limit the fault current under certain conditions. A resistive grounding system introduces resistance to limit fault current but is still connected to the main system, unlike a separately derived system, which maintains that isolation. This fundamental characteristic of being free from the direct influence of the main system is what defines a separately derived system.