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9.3 DISTANCE ELEMENTS
j) FAULT-TYPE CHARACTERISTIC
The fault-type characteristic applies to ground elements only and is achieved by checking the angle between:
A ground element:
B ground element:
C ground element:
The limit angle of the comparator is not adjustable and equals 50°. The fault-type characteristic is intended to block the
ground distance elements during double-line-to-ground faults.
k) ZERO-SEQUENCE DIRECTIONAL CHARACTERISTIC
The extra zero-sequence characteristic applies to ground zones 2 and higher and is achieved by checking angles between:
A ground element:
B ground element:
C ground element:
The limit angle of the comparator is not adjustable and equals 90°. The zero-sequence directional characteristic improves
directional integrity for time-delayed operations after the memory expires.
l) OVERCURRENT SUPERVISION
The overcurrent supervision responds to the following currents:
AB phase element:
BC phase element:
CA phase element:
A, B, C ground element:
The following tables summarize the characteristics of the distance elements
Table 9–1: DIRECTIONAL MHO PHASE DISTANCE FUNCTIONS
CHARACTERISTIC
Variable mho
Reactance
Directional
Table 9–2: DIRECTIONAL MHO GROUND DISTANCE FUNCTIONS
CHARACTERISTIC
Variable mho
Reactance
Directional
Directional
Fault-type
Zero-sequence
9
Table 9–3: DIRECTIONAL QUADRILATERAL PHASE DISTANCE FUNCTIONS
CHARACTERISTIC
Reactance
Directional
Right Blinder
Left Blinder
9-24
I_0
and
I
_2;
A
I_0
and
I
_2
B
I_0
and
I
_2
C
I_0 Z
and
–V_0
D
I_0 Z
and
–V_0
D
I_0 Z
and
–V_0
D
(I
– I
) /
3
A
B
(I
– I
) /
3
B
C
(I
– I
) /
3
C
A
| 3 I_0 – 0.05 × I_1 |
COMPARATOR INPUTS
I Z – V
V_1M
I Z – V
I Z
I Z
V_1M
D
COMPARATOR INPUTS
I Z – V
V_1M
I Z – V
I_0 Z
I_0 Z
V_1M
D
I_2 Z
V_1M
D
I_0
I_2
I_0 Z
–V_0
D
COMPARATOR INPUTS
I Z – V
I Z
V_1M
D
I Z
– V
R
I Z
– V
L
L90 Line Current Differential System
DIR COMP LIMIT
DIR COMP LIMIT
DIR COMP LIMIT (removed when 3I_0 > OC SUPV and
50°(removed during open pole conditions or when 3I_0 > OC
SUPV and I_2 < CUTOFF)
90° (zones 2 and higher only; removed for zones 2 and higher
during open pole conditions)
I Z
I Z
R
I Z
L
9 THEORY OF OPERATION
LIMIT ANGLE
COMP LIMIT
COMP LIMIT
LIMIT ANGLE
COMP LIMIT
COMP LIMIT
I_2 < CUTOFF)
LIMIT ANGLE
COMP LIMIT
DIR COMP LIMIT
90°
90°
GE Multilin
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