In distribution protection, selective coordination means only the protective device nearest the fault opens. Which term describes this behavior?

• A. Selective
• B. Selective coordination
• C. Coordinated
• D. Isolated

Answer: (A)

In protection philosophy, the aim is to have the protective device closest to a fault trip, keeping the rest of the system in service. This behavior is described by selective coordination, meaning the protection system is arranged so that the device nearest to the fault clears it and upstream devices stay healthy. That precise idea—tripping only the device in the faulted zone—is what selective coordination captures. The other terms are less exact: describing the action as merely “selective” leaves out the coordinated timing and setting relationships; “coordinated” is too broad and could apply to many different schemes; and “isolated” describes the result (the fault is isolated) rather than the mechanism that ensures the correct device acts. The key takeaway is that selective coordination ensures only the protective device closest to the fault opens.