Restricted Ground Fault - GE T60 Instruction Manual

5 SETTINGS
SETTING
GROUND IOC1
FUNCTION:
Enabled = 1
SETTING
GROUND IOC1
SOURCE:
IG
SETTING
GROUND IOC1
BLOCK:
Off = 0
d) RESTRICTED GROUND FAULT (ANSI 87N, IEC PNDF)

PATH: SETTINGS GROUPED ELEMENTS
 RESTRICTED GROUND
 FAULT 1
MESSAGE
MESSAGE
MESSAGE
MESSAGE
MESSAGE
MESSAGE
MESSAGE
MESSAGE
As of T60 firmware revision 3.20, the definition of the restraining signal has been significantly changed
compared to previous versions. The restraint during external faults is generally not lower, and often much
higher, compared to the previous definition of the restraining signal (enhanced security). The restraint on
NOTE
internal faults has been greatly reduced compared to previous versions (enhanced sensitivity), particularly
during low-current internal faults. Using time delay as a means of dealing with CT saturation is no longer
obligatory; pickup and slope are the primary means of addressing CT saturation. Increasing the slope set-
ting is recommended when migrating from the 3.1x or earlier firmware revisions. The default value for the
slope has been changed from 10% to 40%.
Restricted ground fault (RGF) protection provides sensitive ground fault detection for low-magnitude fault currents, primar-
ily faults close to the neutral point of a wye-connected winding. An internal ground fault on an impedance grounded wye
winding will produce a fault current dependent on the ground impedance value and the fault position on the winding with
respect to the neutral point. The resultant primary current will be negligible for faults on the lower 30% of the winding since
the fault voltage is not the system voltage, but rather the result of the transformation ratio between the primary windings
GE Multilin
SETTINGS
GROUND IOC1 PICKUP
SETTING
DELAY:
GROUND IOC1
GROUND IOC1 RESET
PICKUP:
DELAY:
AND RUN
t
PKP
IG PICKUP
Figure 5–116: GROUND IOC1 SCHEME LOGIC
 
SETTING GROUP 1(6)
RESTD GND FT1
FUNCTION: Disabled
RESTD GND FT1
SOURCE: SRC 1
RESTD GND FT1
PICKUP: 0.080 pu
RESTD GND FT1
SLOPE: 40%
RESTD GND FT1 PICKUP
DELAY: 0.10 s
RESTD GND FT1 RESET
DELAY: 0.00 s
RESTD GND FT1 BLOCK:
Off
RESTD GND FT1
TARGET: Self-reset
RESTD GND FT1
EVENTS: Disabled
T60 Transformer Protection System
5.6 GROUPED ELEMENTS
t
RST

GROUND CURRENT

RESTRICTED GROUND FAULT 1(4)

Range: Disabled, Enabled
Range: SRC 1, SRC 2, SRC 3, SRC 4, SRC 5, SRC 6
Range: 0.005 to 30.000 pu in steps of 0.001
Range: 0 to 100% in steps of 1
Range: 0.00 to 600.00 s in steps of 0.01
Range: 0.00 to 600.00 s in steps of 0.01
Range: FlexLogic operand
Range: Self-reset, Latched, Disabled
Range: Disabled, Enabled
FLEXLOGIC OPERANDS
GROUND IOC1 PKP
GROUND IOIC DPO
GROUND IOC1 OP
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827037A5.VSD
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