🔍 Key Concepts

• Parallel operation of AC generators and how load is shared between them • What happens to power flow if one prime mover (engine) stops while the generator is still connected to the bus • The purpose of reverse power protection and overload protection on generator circuit breakers

💭 Think About

• If two generators are in parallel and one engine suddenly stops providing torque, think about which way the power will try to flow: from the dead machine to the bus, or from the live bus to the dead machine? • Which protective relay acts first when power starts to flow in the wrong direction versus when current becomes too large? Consider the time it takes for each to operate. • If only one generator is left carrying the whole load, under what condition would its breaker trip on overload, and would that be instantaneous or time‑delayed?

✅ Before You Answer

• Verify which device is designed specifically to detect power flowing into a generator instead of out of it. • Consider whether an AC generator that has lost its driving engine will tend to slow down and become a motor if it remains connected to an energized bus. • Check which trip condition – reverse power or overload – is normally set with a faster response in standard shipboard generator protection.