GE L90 Instruction Manual page 766
Line current differential system
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- Communications manual (532 pages) ,
- Instruction manual (486 pages)
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DISTANCE ELEMENTS
•
CA phase element — (I
•
A ground element — I
•
B ground element — I
•
C ground element — I
The blinders apply to the Quad characteristic only.
10.3.3.9 Left blinder characteristic
The left blinder characteristic is achieved by checking the angle between the following signals:
•
AB phase element — (I
•
BC phase element — (I
•
CA phase element — (I
•
A ground element — I
•
B ground element — I
•
C ground element — I
The blinders apply to the Quad characteristic only.
10.3.3.10 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.
For phase elements, first voltages and then currents are checked to ensure permission to phase distance for any types of
faults except SLG faults. First, the SLG fault type is determined by detecting one phase voltage depressed while two others
are not by using the following equation.
where VA_LOW = |V_A + V_0| < 0.98 *|VBC| /
Additionally, the multi-phase fault is determined if at least two phase voltages are below 85% of the nominal:
M-PH = (VA < 0.85pu & VB < 0.85 pu) OR (VB < 0.85pu & VC < 0.85pu) OR (VC < 0.85 pu & VA < 0.85 pu)
Permission is always granted to phase distance by setting FLGAB, FLGBC, and FLGCA flags to logic '1,' unless the following
condition is satisfied:
meaning that if there are negative- and zero-sequence currents present in the fault signal, voltage signatures indicate the
presence of the SLG fault and not a multi-phase fault. If at least one of these conditions is not satisfied, permission
continues to be granted to all phase distance loops.
But in case this condition is satisfied, angles between I_0 and I_2 are additionally checked to still grant permission to the
phase distance loops, shown as follows for the ABC rotation:
If | ang(I_0) - ang(I_2) + 120° | < 70°, then FLGAB = 1
If | ang(I_0) - ang(I_2)+240° | < 70°, then FLGCA = 1
10
If | ang(I_0) - ang(I_2) | < 70°, then FLGBC = 1
Phase distance fault type supervision is suppressed during open pole conditions and for delta connected VTs.
10-24
– I
) × Z
– (V
– V
) and (I
C
A
R
C
A
× Z
+ I_0 × K0 × Z
+ I
× K0M × Z
A
R
R
G
× Z
+ I_0 × K0 × Z
+ I
× K0M × Z
B
R
R
G
× Z
+ I_0 × K0 × Z
+ I
× K0M × Z
C
R
R
G
– I
) × Z
– (V
– V
) and (I
A
B
L
A
B
– I
) × Z
– (V
– V
) and (I
B
C
L
B
C
– I
) × Z
– (V
– V
) and (I
C
A
L
C
A
× Z
+ I_0 × K0 × Z
+ I
× K0M × Z
A
L
L
G
× Z
+ I_0 × K0 × Z
+ I
× K0M × Z
B
L
L
G
× Z
+ I_0 × K0 × Z
+ I
× K0M × Z
C
L
L
G
_2
A
_2
B
_2
C
SLG = (VA_LOW & NOT VB_LOW & NOT VC_LOW) OR
(NOT VA_LOW & VB_LOW & NOT VC_LOW) OR
(NOT VA_LOW & NOT VB_LOW & VC_LOW)
, similarly for B and C phases.
PKP_I0 & PKP_I2 & SLG & NOT M-PH
CHAPTER 10: THEORY OF OPERATION
– I
) × Z
C
A
R
– V
and I
× Z
+ I_0 × K0 × Z
R
A
A
R
– V
and I
× Z
+ I_0 × K0 × Z
R
B
B
R
– V
and I
× Z
+ I_0 × K0 × Z
R
C
C
R
– I
) × Z
A
B
L
– I
) × Z
B
C
L
– I
) × Z
C
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
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
+ I
× K0M × Z
R
G
R
+ I
× K0M × Z
R
G
R
+ I
× K0M × Z
R
G
R
+ I
× K0M × Z
L
G
L
+ I
× K0M × Z
L
G
L
+ I
× K0M × Z
L
G
L
Eq. 10-37
Eq. 10-38
Eq. 10-39
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