ZPE
I
1
L
•
ZPE
•
L1
I
-
U
=
U
L1
comp1
ß
jX
I
L1L2
R
vPe
Re
Z
•
I
-
L1
U
L1
)
L1
=
ZRevPE
•
(-I
-
1
L
2
comp
U
U
en 06000465.vsd
2
I
1
L L
•
•
IEC06000465 V1 EN
Figure 71:
Simplified offset mho characteristic and voltage vector for phase L1-
to-earth fault
Operation occurs if 90≤β≤270.
Offset mho, forward direction
In the same way as for phase-to-phase fault, selection of forward direction of offset
mho will introduce an extra criterion for operation. Beside the basic criteria for offset
mho according to equation
and 90≤β≤270, also the criteria that the angle φ between
the voltage and the current must lie between the blinders in second and fourth
quadrant. See figure
. Operation occurs if 90≤β≤270 and
ArgDir
≤φ≤
ArgNegRes.
where
ArgDir
is the setting parameter for directional line in fourth quadrant in the directional element,
ZDMRDIR.
ArgNegRes
is the setting parameter for directional line in second quadrant in the directional element,
ZDMRDIR.
β
is calculated according to equation
1MRK502052-UEN B
Section 7
Impedance protection
191
Technical manual
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