GE D60 Instruction Manual page 495

9 THEORY OF OPERATION
j) FAULT-TYPE CHARACTERISTIC
The fault-type characteristic applies to ground elements only and is achieved by checking the angle between:
A ground element: I_0
B ground element: I_0
C ground element: I_0
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:
I_0 × Z
A ground element:
I_0 × Z
B ground element:
I_0 × Z
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: (I
A
BC phase element: (I
B
CA phase element: (I
C
A, B, C ground element: | 3 × I_0 – 0.05 × I_1 |
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
Table 9–3: DIRECTIONAL QUADRILATERAL PHASE DISTANCE FUNCTIONS
CHARACTERISTIC
Reactance
Directional
Right Blinder
Left Blinder
GE Multilin
and I _2;
A
and I _2
B
and I _2
C
and –V_0
D
and –V_0
D
and –V_0
D
– I ) / 3
B
– I ) / 3
C
– I ) / 3
A
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
I × Z V_1M
D
I × Z I × Z
– V
R
I × Z I × Z
– V
L
D60 Line Distance Protection System
LIMIT ANGLE
COMP LIMIT
COMP LIMIT
DIR COMP LIMIT
LIMIT ANGLE
COMP LIMIT
COMP LIMIT
DIR COMP LIMIT
DIR COMP LIMIT (removed when 3I_0 > OC SUPV and
I_2 < CUTOFF)
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)
R
L
9.1 DISTANCE ELEMENTS
LIMIT ANGLE
COMP LIMIT
DIR COMP LIMIT
90°
90°
9
9-5