🔍 Key Concepts

• Follow the fault trip signal paths from OCIT/OC/NPS, RP, and UV/OV/UF/OF into the block labeled LO. • Think about what a master lock‑out or lock‑out relay does in an alternator protection scheme compared with a simple pressure switch. • Note where mechanical/engine protections (like lube oil pressure) are usually shown versus where electrical protections are grouped in a generator one‑line diagram.

💭 Think About

• Is the component labeled LO receiving inputs from several different electrical protection devices, or is it connected to a lube oil system? What does that suggest about its function? • If a device trips the generator circuit breaker and sends a signal to the alarm system for a variety of electrical faults, what kind of relay or function is it likely to be? • Which answer choices talk about mechanical/prime mover protection and which refer to an electrical fault trip / lock‑out device? How does the drawing group these functions?

✅ Before You Answer

• Verify whether any lube oil lines, pumps, or pressure symbols are shown connected to LO in the diagram. • Check that the signals feeding LO are all from electrical protective relays (overcurrent, reverse power, under/over voltage, under/over frequency, etc.). • Confirm which answer choice best matches a device that provides a common trip and alarm for multiple electrical fault conditions on the alternator.