GE L90 Instruction Manual page 279
L90 line current differential system ur series
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5 SETTINGS
quadrilateral characteristic and should be set with consideration to the maximum load current and required resistive
coverage.
•
GND DIST Z1 QUAD RGT BLD RCA: This setting defines the angular position of the right blinder of the quadrilateral
characteristic (see the Quadrilateral distance characteristic figure).
•
GND DIST Z1 QUAD LFT BLD: This setting defines the left blinder position of the quadrilateral characteristic along the
resistive axis of the impedance plane (see the Quadrilateral distance characteristic figure). The angular position of the
blinder is adjustable with the use of the
lateral characteristic and should be set with consideration to the maximum load current.
•
GND DIST Z1 QUAD LFT BLD RCA: This setting defines the angular position of the left blinder of the quadrilateral
characteristic (see the Quadrilateral distance characteristic figure).
•
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.
•
GND DIST Z1 POS-SEQ SUPV RESTR: This setting enhances ground distance security against spurious neutral cur-
rent during three-phase faults, phase-to-phase faults, and switch-off transients. To accomplish this, a small amount of
positive-sequence current is subtracted from the neutral current magnitude to prevent the supervising current from sat-
isfying the ground distance operate condition. This restraint is especially beneficial for instantaneous zone 1. Setting
this value to zero removes the positive-sequence restraint.
•
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.
FLEXLOGIC OPERAND
GND DIST Z1 PKP A
FLEXLOGIC OPERAND
GND DIST Z1 PKP B
FLEXLOGIC OPERAND
GND DIST Z1 PKP C
FLEXLOGIC OPERANDS
GND DIST Z1 SUPN IN
OPEN POLE OP **
** D60, L60, and L90 only. Other UR-series models apply regular current seal-in for zone 1.
GE Multilin
GND DIST Z1 QUAD LFT BLD RCA
. 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
SETTING
GND DIST Z1 DELAY
T
PKP
0
T
PKP
0
T
PKP
0
AND
Figure 5–69: GROUND DISTANCE ZONE 1 OP SCHEME
L90 Line Current Differential System
5.6 GROUPED ELEMENTS
setting. This setting applies only to the quadri-
FLEXLOGIC OPERANDS
GND DIST Z1 OP A
GND DIST Z1 OP B
AND
GND DIST Z1 OP C
OR
FLEXLOGIC OPERAND
AND
GND DIST Z1 OP
OR
OR
AND
OR
5
837018A7.CDR
5-143
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