GE L90 Instruction Manual page 181

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 through 3 apply additional zero-
sequence directional supervision. See Chapter 8 for additional details.
Three zones of ground distance protection are provided. Each 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 three zones as entered under the
SIGNAL SOURCE
!"
SETTINGS GROUPED ELEMENTS
2. The setting (common for both phase and ground elements for all three zones as entered under the
MEMORY DURATION
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SETTINGS GROUPED ELEMENTS
The common distance settings noted at the start of the Distance section must be properly chosen for correct operation of
the ground distance elements.
Although all three zones can be used as either instantaneous elements (pickup [
nals) or time-delayed elements (operate [
reaching tripping mode.
Ensure that the
PHASE VT SECONDARY VOLTAGE
menu) is set correctly to prevent improper operation of associated memory action.
BANK
WARNING
• GND DIST Z1 DIR: All three zones are reversible. The forward direction is defined by the
the reverse direction is shifted by 180° from that angle. The non-directional zone spans between the forward reach
impedance defined by the
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)
!
SETTING GROUP 1(6)
] FlexLogic™ signals), only Zone 1 is intended for the instantaneous under-
OP
(see the
and
GND DIST Z1 REACH GND DIST Z1 RCA
and
GND DIST Z1 REV REACH RCA
L90 Line Differential Relay
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).
DISTANCE
!" menu).
DISTANCE
] and dropout [
PKP
!"
SETTINGS SYSTEM SETUP
settings, and the reverse reach impedance defined
settings.
5.5 GROUPED ELEMENTS
] FlexLogic™ sig-
DPO
! !"
AC INPUTS VOLTAGE
setting and
GND DIST Z1 RCA
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