GE L90 Instruction Manual page 293

5 SETTINGS
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The ground mho distance function uses a dynamic 100% memory-polarized mho characteristic with additional reactance,
directional, current, and phase selection supervising characteristics. The ground quadrilateral distance function is com-
posed of a reactance characteristic, right and left blinders, and 100% memory-polarized directional, overcurrent, and phase
selection supervising characteristics.
When set to non-directional, the mho function becomes an offset mho with the reverse reach controlled independently from
the forward reach, and all the directional characteristics removed. When set to non-directional, the quadrilateral function
applies a reactance line in the reverse direction instead of the directional comparators.
The reactance supervision for the mho function uses the zero-sequence current for polarization. The reactance line of the
quadrilateral function uses either zero-sequence or negative-sequence current as a polarizing quantity. The selection is
controlled by a user setting and depends on the degree of non-homogeneity of the zero-sequence and negative-sequence
equivalent networks.
The directional supervision uses memory voltage as polarizing quantity and both zero- and negative-sequence currents as
operating quantities.
The phase selection supervision restrains the ground elements during double-line-to-ground faults as they – by principles
of distance relaying – may be inaccurate in such conditions. Ground distance zones 1 and higher apply additional zero-
sequence directional supervision. See chapter 8 for additional details.
Each ground distance zone is configured individually through its own setting menu. All of the settings can be independently
modified for each of the zones except:
1. The setting (common for both phase and ground elements for all zones as entered under the
SIGNAL SOURCE
GROUPED ELEMENTS
2. The setting (common for both phase and ground elements for all zones as entered under the
MEMORY DURATION
TINGS GROUPED ELEMENTS
The common distance settings noted at the start of this section must be properly chosen for correct operation of the ground
distance elements.
Although all ground distance zones can be used as either instantaneous elements (pickup [
Logic™ signals) or time-delayed elements (operate [
under-reaching tripping mode.
Ensure that the
PHASE VT SECONDARY VOLTAGE
menu) is set correctly to prevent improper operation of associated memory action.
BANK
NOTE
• GND DIST Z1 DIR: All ground distance zones are reversible. The forward direction is defined by the
setting and the reverse direction is shifted by 180° from that angle. The non-directional zone spans between the for-
ward reach impedance defined by the
ance defined by the
GND DIST Z1 REV REACH
• GND DIST Z1 SHAPE: This setting selects the shape of the ground distance characteristic between the mho and
quadrilateral characteristics. The selection is available on a per-zone basis.
The directional and non-directional quadrilateral ground distance characteristics are shown below. The directional and
non-directional mho ground distance characteristics are the same as those shown for the phase distance element in
the previous sub-section.
GE Multilin
GND DIST Z1 VOLT
LEVEL: 0.000 pu
GND DIST Z1
DELAY: 0.000 s
GND DIST Z1 BLK:
Off
GND DIST Z1
TARGET: Self-Reset
GND DIST Z1
EVENTS: Disabled
SETTING GROUP 1(6) DISTANCE
SETTING GROUP 1(6)
] FlexLogic™ signals), only zone 1 is intended for the instantaneous
OP
(see the
GND DIST Z1 REACH
and
GND DIST Z1 REV REACH RCA
L90 Line Current Differential System
Range: 0.000 to 5.000 pu in steps of 0.001
Range: 0.000 to 65.535 s in steps of 0.001
Range: FlexLogic™ operand
Range: Self-Rest, Latched, Disabled
Range: Disabled, Enabled
menu).
menu).
DISTANCE
SETTINGS SYSTEM SETUP
and settings, and the reverse reach imped-
GND DIST Z1 RCA
settings.
5.6 GROUPED ELEMENTS
SETTINGS
SET-
] and dropout [ ] Flex-
PKP DPO
AC INPUTS VOLTAGE
GND DIST Z1 RCA
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