GE L90 Instruction Manual page 183

5 SETTINGS
• GND DIST Z1 ZOM/Z1 ANG: This setting specifies the angle difference between the mutual zero-sequence imped-
ance between the lines and the positive-sequence impedance of the protected line.
• GND DIST Z1 REACH: This setting defines the reach of the zone for the forward and reverse applications. In non-
directional applications, this setting defines the forward reach of the zone. The reverse reach impedance in non-direc-
tional applications is set independently. The angle of the reach impedance is entered as the
The reach impedance is entered in secondary ohms.
• GND DIST Z1 RCA: This setting specifies the characteristic angle (similar to the 'maximum torque angle' in previous
technologies) of the ground distance characteristic for the forward and reverse applications. In the non-directional
applications this setting defines the forward reach of the zone. The reverse reach impedance in the non-directional
applications is set independently. This setting is independent from the
angle of an extra directional supervising function).
The relay internally performs zero-sequence compensation for the protected circuit based on the values
entered for
GND DIST Z1 Z0/Z1 MAG
NOTE pensation for mutual coupling based on the values entered for
(see Chapter 8 for details). The
ANG
terms of positive sequence quantities.
• GND DIST Z1 REV REACH: This setting defines the reverse reach of the zone set to non-directional (
setting). The value must be entered in secondary ohms. This setting does not apply when the zone direction is set to
"Forward" or "Reverse".
• GND DIST Z1 REV REACH RCA: This setting defines the angle of the reverse reach impedance if the zone is set to
non-directional (
GND DIST Z1 DIR
"Reverse".
• GND DIST Z1 POL CURRENT: This setting applies only if the
polarizing current used by the reactance comparator of the quadrilateral characteristic. Either the zero-sequence or
negative-sequence current could be used. Refer to Chapters 8 and 9 for additional information. In general, a variety of
system conditions must be examined to select an optimum polarizing current. This setting becomes less relevant when
the resistive coverage and zone reach are set conservatively. Also, this setting is more relevant in lower voltage appli-
cations such as on distribution lines or cables, as compared with high-voltage transmission lines. This setting applies
to both the Z1 and reverse reactance lines if the zone is set to non-directional.
• GND DIST Z1 NON-HOMOGEN ANG: This setting applies only if the
a method to correct the angle of the polarizing current of the reactance comparator for non-homogeneity of the zero-
sequence or negative-sequence networks. Refer to Chapters 8 and 9 for additional information. In general, a variety of
system conditions must be examined to select this setting. In many applications this angle is used to reduce the reach
at high resistances in order to avoid overreaching under far-out reach settings and/or when the sequence networks are
greatly non-homogeneous. This setting applies to both the forward and reverse reactance lines if the zone is set to
non-directional.
• GND DIST Z1 COMP LIMIT: This setting shapes the operating characteristic. In particular, it enables a lens-shaped
characteristic of the mho function and a tent-shaped characteristic of the quadrilateral function reactance boundary. If
the mho shape is selected, the same limit angle applies to mho and supervising reactance comparators. In conjunction
with the mho shape selection, this setting improves loadability of the protected line. In conjunction with the quadrilat-
eral characteristic, this setting improves security for faults close to the reach point by adjusting the reactance boundary
into a tent-shape.
• GND DIST Z1 DIR RCA: Selects the characteristic angle (or 'maximum torque angle') of the directional supervising
function. If the mho shape is applied, the directional function is an extra supervising function, as the dynamic mho
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
quadrilateral characteristic and should be set with consideration to the maximum load current and required resistive
coverage.
GE Multilin
and
GND DIST Z1 Z0/Z1 ANG
GND DIST Z1 REACH
setting). This setting does not apply when the zone direction is set to "Forward" or
GND DIST Z1 QUAD RGT BLD RCA
L90 Line Differential Relay
5.5 GROUPED ELEMENTS
GND DIST Z1 RCA
setting (the characteristic
GND DIST Z1 DIR RCA
, and if configured to do so, zero-sequence com-
GND DIST Z1 Z0M/Z1 MAG
and should, therefore, be entered in
GND DIST Z1 RCA
is set to "Quad" and controls the
GND DIST Z1 SHAPE
is set to "Quad" and provides
GND DIST Z1 SHAPE
setting. This setting applies only to the
setting.
and
GND DIST Z1 Z0M/Z1
GND DIST Z1 DIR
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