triggered with zone 2 pickup, Z2pick up enumeration has to be selected . If zone 3
select Z3pick up enumeration.
27_COMP: The pickup value of the under voltage seal-in feature can be set using
27_COMP. This is provided in percentage of VBase. Recommended setting is 70%.
timeDelay27: The operate time delay in seconds for the under voltage seal-in. The
recommended time delay is to provide the same trip delay setting as the selected zone
that is, either zone 2 or zone 3.
8.10 Rotor ground
fault protection (64R)using CVGAPC
SEMOD151286-4 v8
The field winding, including the rotor winding and the non-rotating excitation
equipment, is always insulated from the metallic parts of the rotor. The insulation
resistance is high if the rotor is cooled by air or by hydrogen. The insulation resistance
is much lower if the rotor winding is cooled by water. This is true even if the insulation
is intact. A fault in the insulation of the field circuit will result in a conducting path
from the field winding to ground. This means that the fault has caused a field ground
fault.
The field circuit of a synchronous generator is normally ungrounded. Therefore, a
single ground fault on the field winding will cause only a very small fault current. Thus
the ground fault does not produce any damage in the generator. Furthermore, it will not
affect the operation of a generating unit in any way. However, the existence of a single
ground fault increases the electric stress at other points in the field circuit. This means
that the risk for a second ground fault at another point on the field winding has
increased considerably. A second ground fault will cause a field short-circuit with
severe consequences.
The rotor ground fault protection is based on injection of an AC voltage to the isolated
field circuit. In non-faulted conditions there will be no current flow associated to this
injected voltage. If a rotor ground fault occurs, this condition will be detected by the
rotor ground fault protection. Depending on the generator owner philosophy this
operational state will be alarmed and/or the generator will be tripped. An injection unit
RXTTE4 and an optional protective resistor on plate are required for correct rotor
ground fault protection operation.
Rotor ground fault protection can be integrated in the IED among all
other protection functions typically required for generator protection.
How this is achieved by using COMBIFLEX injection unit RXTTE4 is
described in Instruction 1MRG001910.
Section 8 1MRK 502 071-UUS A
Impedance protection
340 Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062
Application manual
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