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3.4.9.2
Rotor Earth Fault Protection (1 to 3 Hz)
7UM62 Manual
C53000-G1176-C149-3
Start up generator and excite to rated voltage. If applicable place measurement
brushes into operation.
The rotor earth fault protection initiates pick-up and, after T-TRIP-RE<< (10 s when
delivered from factory), trip annunciation (LED 2 and LED 1 as group indications for
device pickup and device trip).
The earth resistance calculated by the device can be read out in the earth fault
annunciations as Re.
For generators with excitation via slip rings, the test is repeated for the other slip ring.
Shut down generator. Remove earth fault resistor.
Switch the rotor earth fault protection ROTOR E/F = ON under address 6001.
In Section 3.3.7.2, the rotor earth fault protection was checked with the machine at
stand-still. In order to exclude possible interference on the measurement circuit by the
running generator, and specifically by the excitation system, an additional test during
operation is recommended.
Caution!
Make sure that the checked rotor circuit is completed isolated from the earth, to
avoid that the earthing resistor that is interposed for test purposes causes a
double earth fault!
An earth fault is simulated via a resistor of approximately 90% of the trip resistance
(address 6104 RE<< TRIP). In machines with rotating rectifier excitation (Figure 3-
19 left), the resistor is placed between the measurement slip rings; in machines with
excitation via slip rings (Figure 3-19 right) between one slip ring and earth.
Start up the generator and excite to the rated voltage. If applicable place measure-
ment brushes into operation.
Check the operational measured value Rearth and the pickup indication ("REF 1-3Hz
Fault") and, after T-TRIP-RE<< (10 s on delivery) has expired, check the trip indi-
cation ("REF 1-3Hz Trip") as well.
Set the resistance to approx. 90 % of the warning stage (address 6102 RE< WARN),
read out the operational measured value Rearth, and check the warning message
("REF 1-3Hz Warn"). If there is heavy interference from the excitation system, it may
be necessary to reduce the resistance set for the warning threshold.
Remove the earthing resistor and check the operational measured values as well as
the measuring circuit supervision "REF 1-3Hz open" in fault-free condition. If spon-
taneous indications are issued by the measuring circuit monitoring, reduce the pickup
value (address 6106 Qc) or de-activate the monitoring.
For generators with excitation via slip rings, the test is repeated for the other slip ring.
Shut down generator. Remove earth fault resistor.
Switch the rotor earth fault protection REF 1-3Hz = ON under address 6101.
3.4 Primary Commissioning Tests with the Generator
385
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