GE G60 Instruction Manual page 527

CHAPTER 5: SETTINGS
Ground undercurrent
A brush lift-off condition prevents the field ground detector from operating. This is detected by calculating the RMS value
of the ground current. It normally has a non-zero value due to the capacitance of the field winding. A drop in this signal
indicates an open circuit in the injection path and the field ground under current feature detects this condition.
Field current monitoring
The G60 can monitor the field current via a Hall effect transducer that produces a 4 to 20 mA output. This device must be
wired to a DCmA input of the G60 or a HardFiber Brick. Note that the relay must be configured with a transducer input card
for the former case. Assignment of this signal to the field ground function allows the user to detect a field overcurrent or
undercurrent condition. The maximum and minimum settings configured for scaling of this DCmA input is used to get the
per-unit values of field current.
5.7.18.2 Field ground (ANSI 64F)
SETTINGS  GROUPED ELEMENTS  SETTING GROUP 1(6)  FIELD GROUND PROTECTION  FIELD GROUND
 FIELD
 GROUND
The following settings are available for the field ground fault detector function.
— This setting enables and disables the field ground fault element.
FIELD GROUND FUNCTION
FIELD GROUND INJECTION FREQUENCY
winding for detecting ground faults. The injection frequency selection depends on the value of field winding capacitance to
ground. Use the following formula to set the injection frequency when the field winding capacitance is known in µF.
where
C is in microfarads
F
G60 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL
FIELD GROUND

FUNCTION: Disabled
FIELD GROUND INJECTION

FREQUENCY: 1.0 Hz
INJ CONNECTION TYPE:

Single Point
FIELD GROUND STG1

PICKUP: 20 kΩ
FIELD GROUND STG1

DELAY: 10.0 s
FIELD GROUND STG2

PICKUP: 5 kΩ
FIELD GROUND STG2

DELAY: 3.0 s
FIELD GROUND UC

PICKUP: 1.00 mA
FIELD GROUND UC

DELAY: 1.0 s
FIELD GROUND BLK:

Off
FIELD GROUND

TARGET: Self-reset
FIELD GROUND

EVENTS: Disabled
— This setting specifies the frequency of the signal to be injected into the field
GROUPED ELEMENTS
Range: Disabled, Enabled
Range: 0.1 to 3.0 Hz in steps of 0.1
Range: Single Point, Double Point
Range: 1 to 500 kΩ in steps of 1
Range: 0.1 to 600.0 s in steps of 0.1
Range: 1 to 500 kΩ in steps of 1
Range: 0.1 to 600.0 s in steps of 0.1
Range: 0.05 to 100.00 mA in steps of 0.1
Range: 0.10 to 600.00 s in steps of 0.1
Range: FlexLogic operand
Range: Self-reset, Latched, Disabled
Range: Disabled, Enabled
5
Eq. 5-49
5-313