I
L1
jX
U
L1
f
ArgDir
I
L1
ArgNegRes
IL1·R
en 06000466.vsd
IEC06000466 V1 EN
Figure 72:
Simplified characteristic for offset mho in forward direction for L1-to-
earth fault
Offset mho, reverse direction
In the same way as for offset in forward direction, the selection of offset mho in
reverse direction will introduce an extra criterion for operation compare to the normal
offset mho. The extra is that the angle between the fault voltage and the fault current
shall lie between the blinders in second and fourth quadrant. The operation area in
second quadrant is limited by the blinder defined as 180° -
ArgDir
and in fourth
quadrant
ArgNegRes
+180°, see figure
.
The conditions for operation of offset mho in reverse direction for L1-to-earth fault is
90≤β≤270 and 180°-
Argdir
≤φ≤
ArgNegRes
+180°.
The β is derived according to equation
for the offset mho circle and φ is the angle
between the voltage and current.
Section 7
1MRK502052-UEN B
Impedance protection
192
Technical manual
Summary of Contents for Relion REG670
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