314 HANDBOOK OF ELECTRICAL ENGINEERING
- Reverse active power (32).
- Negative phase sequence (46).
- Stator earth fault current (51 G) and (64).
- Over terminal voltage, (59) Note 1.
- Under terminal voltage, (27) Note 1.
- Overfrequency, (81) Note 2.
- Underfrequency, (81) Note 2.
- Winding temperature (26).
Note 1: These can be combined in one voltage relay.
Note 2: These can be combined in one frequency relay.
A typical scheme that contains most of these relays is shown in Figure 12.2.
12.2.2 Overcurrent
12.2.2.1 Response of a generator to a major fault
When a major fault occurs externally from the generator but near to the generator stator terminals or
near its switchgear, two reactions take place:-
Figure 12.2 Protective devices for a high voltage generator.