What is the term for the phenomenon when two SSGTGs are operating in parallel and one generator loses its prime mover?

The phenomenon where two synchronous generators are operating in parallel and one generator loses its prime mover is referred to as reverse power. In this situation, the generator that has lost its prime mover is unable to produce power and instead begins to draw power from the connected grid or the other generator. This creates an undesirable condition where the generator is essentially functioning as a motor, consuming power rather than generating it, which can lead to damage and hazardous conditions.

The reverse power relay is specifically designed to detect this condition. When it senses that power is flowing in the reverse direction, meaning energy is being taken from the generator rather than supplied, it can take protective actions to isolate the problematic generator. This helps maintain system stability and prevents potential damage to both the generator and connected equipment.

The other choices do not accurately represent this specific phenomenon. Back feed relays are used to prevent reverse energy flow in general, but they do not specifically address a generator losing its prime mover. Phase loss relays focus on the detection of phase loss in a three-phase system instead of the operational status of generators in parallel. Load shedding relays are involved in the automatic disconnection of certain loads during overloading conditions, rather than the dynamic interaction of generators.