GE T60, Instruction Manual

Page: 342 / 796

5-196 T60 Transformer Protection System GE Multilin
5.6 GROUPED ELEMENTS 5 SETTINGS
5
characteristic itself is a directional one. In conjunction with the quadrilateral shape selection, this setting defines the
only directional function built into the ground distance element. The directional function uses memory voltage for polar-
ization.
• GND DIST Z1 DIR COMP LIMIT : This setting selects the comparator limit angle for the directional supervising function.
• GND DIST Z1 QUAD RGT BLD : This setting defines the right 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
GND DIST Z1 QUAD RGT BLD RCA
setting. This setting applies only to the
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
GND DIST Z1 QUAD LFT BLD RCA
setting. This setting applies only to the quadri-
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. 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
setting specified in the
PRODUCT SETUP

DISPLAY PROPERTIES
menu
• 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
. Effectively, this setting facilitates dynamic current-based reach reduction. In
non-directional applications (
GND DIST Z1 DIR
set to “Non-directional”), this setting applies only to the forward reach of
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.