🔍 Key Concepts

• Reverse power condition in an alternator connected in parallel with a bus • Difference between an alternator supplying power to the bus and an alternator motoring from the bus • How the RP relay is connected in the diagram relative to current transformers (CTs) and the bus

💭 Think About

• Look at the power flow: under a healthy condition, in which direction should real power flow between the generator and the bus, and what happens electrically if the prime mover torque is lost? • In the diagram, the RP relay is sensing current and voltage. What change in kW (real power) and its direction would cause this relay to operate? • Which option describes an electrical power-flow problem (kW direction) rather than a mechanical reversal or field polarity issue?

✅ Before You Answer

• Verify which choice specifically mentions the generator acting as a motor instead of a source. • Check which options are actually protected by other relays in a standard protection scheme (phase sequence, field polarity, mechanical reverse rotation) rather than by RP. • Confirm from the illustration that RP is tied into the fault trip line that responds to abnormal power flow direction, not to phase sequence or field polarity.