ABB RELION 670 Series Technical Manual page 231

1MRK 502 066-UUS B
ANSI07000111 V1 EN-US
Figure 101: Simplified offset mho characteristic in forward direction for phase A-to-B fault
Offset mho, reverse direction
The operation area for offset mho in reverse direction is according to figure 102. The operation
area in second quadrant is
Operation occurs if 90≤β≤270 and 180° -
The β is derived according to equation for the mho circle and φ is the angle between the voltage
and current.
Technical manual
I jX
AB
ZPP
V
AB
ArgNegRes
f
I
AB
ArgDir
ArgNegRes +180°.
en07000111_ansi
ArgDir ≤φ ≤ ArgNegRes + 180°
Section 7
Impedance protection
SEMOD154224-265 v4
225