Manual MRI3 GB
Woodward
DOK-TD-MRI3 Rev.A
23
4.4 Earth fault protection
4.4.1 Generator
stator
earth fault protection
With the generator neutral point earthed as shown in Figure 4.7 the MRI3 picks up only to phase
earth faults between the generator and the location of the current transformers supplying the relay.
Earth faults beyond the current transformers, i.e. on the consumer or line side, will not be detected.
Figure 4.7: Generator stator earth fault protection
4.4.2 System earth fault protection
With the generator neutral point earthed as shown in Figure 4.8, the MRI3 picks up only to earth
faults in the power system connected to the generator. It does not pick up to earth faults on the ge-
nerator terminals or in generator stator.
Figure 4.8: System earth fault protection