where
U
L1L2
EQUATION1790 V2
EN
is the voltage vector difference between phases L1 and L2
I
L1L2
EQUATION1791 V2
EN
is the current vector difference between phases L1 and L2
ZPP
is the positive sequence impedance setting for phase-to-phase fault
U
pol
is the polarizing voltage
The polarized voltage consists of 100% memorized positive sequence voltage
(UL1L2 for phase L1 to L2 fault). The memorized voltage will prevent collapse of the
Mho circle for close in faults.
Operation occurs if 90≤β≤270
ZPP
I
2
L
1
L
•
L1L2
comp
U
=
U
ß
I
L1L2·
X
I
L1L2
·R
-
ZPP
I
2
L
1
L
•
2
L
1
L
U
pol
U
en07000109.vsd
IEC07000109 V1 EN
Figure 66:
Simplified mho characteristic and vector diagram for phase L1-to-L2
fault
Offset Mho
The characteristic for offset mho is a circle where two points on the circle are the
setting parameters
ZPP
and
ZRevPP
. The vector ZPP in the impedance plane has the
settable angle
AngZPP
and the angle for
ZRevPP
is
180°
.
1MRK502052-UEN B
Section 7
Impedance protection
185
Technical manual
Summary of Contents for Relion REG670
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