GE D30 Instruction Manual page 457
Line distance protection system
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- Instruction manual (686 pages) ,
- Communications manual (532 pages) ,
- Instruction manual (636 pages)
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CHAPTER 9: THEORY OF OPERATION
•
AB phase element — (I
A
•
BC phase element — (I
B
•
CA phase element — (I
C
•
A ground element — I
A
•
B ground element — I
B
•
C ground element — I
C
The blinders apply to the Quad characteristic only.
9.1.3.10 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 and I
•
B ground element — I_0 and I
•
C ground element — I_0 and I
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. First checked is if the
ground elements fault-type comparator, shown above, does not operate in the corresponding distance loop. Second, the
angle between (I_1 - I_1mem) and I_2 is checked to be within 45° in the corresponding phase distance loop. I_1mem is the
pre-fault positive sequence current, which is updated with the actual I_1 phasor of two cycles before. Upon 50DD
assertion, I_1mem stops updating and is sealed-in for 500 ms. After this 500 ms seal-in timer expires, the fault-type
permission for phase distance is checked. If such permission was already given prior to the 500 ms timer expiry, this
permission is extended in a per zone and per loop basis as long as the corresponding phase distance element in this zone
and this loop continues being picked up. Supervision is suppressed during open pole conditions and the angle is not
checked during three-phase faults.
9.1.3.11 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 — I_0 × Z
•
•
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.
9.1.3.12 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
Comparator inputs
Variable mho
I × Z – V
Reactance
I × Z – V
D30 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
– I
) × Z
– (V
– V
) and (I
B
L
A
B
A
– I
) × Z
– (V
– V
) and (I
C
L
B
C
B
– I
) × Z
– (V
– V
) and (I
A
L
C
A
C
× Z
+ I_0 × K0 × Z
+ I
× K0M × Z
L
L
G
× Z
+ I_0 × K0 × Z
+ I
× K0M × Z
L
L
G
× Z
+ I_0 × K0 × Z
+ I
× K0M × Z
L
L
G
_2
A
_2
B
_2
C
and –V_0
D
and –V_0
D
and –V_0
D
– I
) /
3
B
– I
) /
3
C
– I
) /
3
A
V_1M
I × Z
– I
) × Z
B
L
– I
) × Z
C
L
– I
) × Z
A
L
– V
and I
× Z
+ I_0 × K0 × Z
L
A
A
L
– V
and I
× Z
+ I_0 × K0 × Z
L
B
B
L
– V
and I
× Z
+ I_0 × K0 × Z
L
C
C
L
Limit angle
COMP LIMIT
COMP LIMIT
DISTANCE ELEMENTS
+ I
× K0M × Z
L
G
L
+ I
× K0M × Z
L
G
L
+ I
× K0M × Z
L
G
L
9-5
9
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