Functions
2.3 Directional Overcurrent Protection 67, 67N
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
106
Table 2-7
Voltage and Current Values for the Determination of Fault Direction in a Phase Element
Direction Determination of Directional Phase Elements
As already mentioned, the direction determination is performed by determining the phase angle between the
fault current and the reference voltage. In order to satisfy different network conditions and applications, the ref-
erence voltage can be rotated by an adjustable angle. In this way, the vector of the rotated reference voltage
can be closely adjusted to the vector of the fault current in order to provide the best possible result for the di-
rection determination. Figure 2-27 clearly shows the relationship for the directional phase element based on a
single-pole ground fault in Phase A. The fault current
I
scA
follows the fault voltage by fault angle
ϕ
sc
. The refer-
ence voltage, in this case V
BC
for the directional phase element A, is rotated by the setting value
1519
ROTATION ANGLE
, positively counter-clockwise. In this case, a rotation by +45°.
Figure 2-27
Rotation of the reference voltage, directional phase element
Pickup
Selected current
Allocated voltage
A
I
A
V
B
- V
C
B
I
B
V
C
- V
A
C
I
C
V
A
- V
B
A, B with
I
A
>
I
B
I
A
V
B
- V
C
A, B with
I
A
=
I
B
I
A
V
B
- V
C
A, B with
I
A
<
I
B
I
B
V
C
- V
A
B, C with
I
B
>
I
C
I
B
V
C
- V
A
B, C with
I
B
=
I
C
I
B
V
C
- V
A
B, C with
I
B
<
I
C
I
C
V
A
- V
B
C, A with
I
C
>
I
A
I
C
V
A
- V
B
C, A with
I
C
=
I
A
I
A
V
B
- V
C
C, A with
I
C
<
I
A
I
A
V
B
- V
C
A, B, C with
I
A
>(
I
B
,
I
C
)
I
A
V
B
- V
C
A, B, C with
I
B
>(
I
A
,
I
C
)
I
B
V
C
- V
A
A, B, C with
I
C
>(
I
A
,
I
B
)
I
C
V
A
- V
B
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