GE D30 Instruction Manual page 293

5 SETTINGS
• GND DIST Z1 SUPV: The ground distance elements are supervised by the magnitude of the neutral (3I_0) current.
The current supervision pickup should be set less than the minimum 3I_0 current for the end of the zone fault, taking
into account the desired fault resistance coverage to prevent maloperation due to VT fuse failure. Settings less than
0.2 pu are not recommended and should be applied with caution. To enhance ground distance security against spuri-
ous neutral current during switch-off transients, three-phase faults, and phase-to-phase faults, a positive-sequence
current restraint of 5% is applied to the neutral current supervision magnitude. This setting should be at least three
times the
CURRENT CUTOFF LEVEL
• GND DIST Z1 VOLT LEVEL: This setting is relevant for applications on series-compensated lines, or in general, if
series capacitors are located between the relaying point and a point for which the zone shall not overreach. For plain
(non-compensated) lines, this setting shall be set to zero. Otherwise, the setting is entered in per unit of the VT bank
configured under the
DISTANCE SOURCE
non-directional applications (
the non-directional zone. See chapters 8 and 9 for additional details and information on calculating this setting value
for applications on series compensated lines.
• GND DIST Z1 DELAY: This setting enables the user to delay operation of the distance elements and implement a
stepped distance backup protection. The distance element timer applies a short drop out delay to cope with faults
located close to the boundary of the zone when small oscillations in the voltages or currents could inadvertently reset
the timer.
• GND DIST Z1 BLK: This setting enables the user to select a FlexLogic operand to block the given distance element.
VT fuse fail detection is one of the applications for this setting.
GE Multilin
setting specified in the
. Effectively, this setting facilitates dynamic current-based reach reduction. In
set to "Non-directional"), this setting applies only to the forward reach of
GND DIST Z1 DIR
Figure 5–67: GROUND DISTANCE Z1 TO Z3 OP SCHEME
D30 Line Distance Protection System

PRODUCT SETUP DISPLAY PROPERTIES
5.6 GROUPED ELEMENTS
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