Ground Distance - GE D30 Instruction Manual
Line distance
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- Instruction manual (686 pages) ,
- Communications manual (532 pages) ,
- Instruction manual (620 pages)
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9 APPLICATION OF SETTINGS
a) NEUTRAL CURRENT SUPERVISION
The current supervision for the ground distance elements responds to an internally calculated neutral current (3 × I_0). The
setting for this element should be based on twice the zero-sequence line capacitance current or the maximum zero-
sequence unbalance under maximum load conditions. This element should not be used to prevent an output when the load
impedance is inside the distance characteristic on a steady state basis.
b) POLARIZING CURRENT AND NON-HOMOGENEITY CORRECTION ANGLE OF THE QUAD CHARACTERISTIC
An ideal reactance line for single-line-to-ground faults is polarized from the fault current flowing through the fault resistance.
Such a line defines constant reach and could be implemented by the following angle comparator:
The relay could only approximate the unknown fault current by the zero-sequence or the negative-sequence currents mea-
sured at the relaying point. Depending on system parameters, either the zero-sequence or the negative-sequence current
presents better approximation of the fault current angle.
Given the equivalent systems shown in the figure below, the angular difference between the zero-sequence or negative-
sequence currents at the relay, and the fault current can be calculated as follows:
where: A is the local equivalent system
B is the remote equivalent system
L is the line
d is the per-unit (pu) intended reach of the zone (typically 0.7 to 0.9).
Z
0A
Z
1A
abs Θ
(
) abs Θ
<
(
)
If
, the zero-sequence network is more homogenous (the zero-sequence current better approximates
0
2
the fault current), and zero-sequence polarizing should be selected. Otherwise, negative-sequence is a better polarizing
signal.
GE Multilin
9.2 DISTANCE ELEMENTS (STEPPED DISTANCE SCHEME)
I Z
×
V vs. j
–
I
⎛
⎞
F
--------------------- -
Θ
angle
angle
=
=
⎝
⎠
0
I
0_RELAY
I
⎛
⎞
F
Θ
--------------------- -
angle
angle
=
=
⎝
⎠
2
I
2_RELAY
I
F
dZ
(1 – d)Z
0L
0L
I
0
dZ
(1 – d)Z
1L
1L
I
2
I
F
Figure 9–1: UNDERSTANDING SYSTEM HOMOGENEITY
D30 Line Distance Relay
×
I
F
Z
Z
Z
+
+
⎛
⎞
0A
0L
0B
------------------------------------------ -
⎝
⎠
Z
(
1 d
)Z
+
–
0B
0L
Z
Z
Z
+
+
⎛
⎞
1A
1L
1B
------------------------------------------ -
⎝
⎠
(
)Z
Z
1 d
+
–
1B
1L
Z
0B
I
2
DEPENDING ON SYSTEM
Z
PARAMETERS, I0 OR I2 MAYBE A
1B
BETTER APPROXIMATION OF THE
FAULT CURRENT ANGLE
9.2.2 GROUND DISTANCE
(EQ 9.1)
(EQ 9.2)
(EQ 9.3)
I
0
I
F
842742A1.CDR
9-3
9
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