GE D30 Instruction Manual page 447

8 THEORY OF OPERATION
j) FAULT-TYPE CHARACTERISTIC
The fault-type supervision applies to ground and phase elements and is achieved as follows.
For ground elements 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. The fault-type supervision is suppressed during open pole
conditions.
Phase elements supervision is applied to block phase distance elements operation during SLG faults. This is done by first
checking if the ground elements fault-type comparator, shown above, does not operate in the corresponding distance loop
and secondly confirming that fault type is matching phase-to-phase or three-phase signatures. See the Addendum at the
beginning of this manual for information.
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:
B ground element: I_0 × Z
C ground element: I_0 × Z
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
| 3 × I_0 – 0.05 × I_1 |
A, B, C ground element:
The following tables summarize the characteristics of the distance elements.
Table 8–1: DIRECTIONAL MHO PHASE DISTANCE FUNCTIONS
CHARACTERISTIC
Variable mho
Reactance
Directional
Fault-type
Table 8–2: DIRECTIONAL MHO GROUND DISTANCE FUNCTIONS
CHARACTERISTIC
Variable mho
Reactance
Directional
Directional
Fault-type
Zero-sequence
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
Not SLG See Addendum
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
D30 Line Distance Protection System
8.1 DISTANCE ELEMENTS
LIMIT ANGLE
COMP LIMIT
COMP LIMIT
DIR COMP LIMIT
Removed during open pole conditions
LIMIT ANGLE
COMP LIMIT
COMP LIMIT
DIR COMP LIMIT
DIR COMP LIMIT
50°
90°
8
8-5