ABB Relion 670 Series Technical Reference Manual page 254

Section 6
Impedance protection
248
where
ArgDir
is the setting parameter for directional line in fourth quadrant in the directional element,
ZDMRDIR (21D).
ArgNegRes
is the setting parameter for directional line in second quadrant in the directional element,
ZDMRDIR (21D).
β is calculated according to equation
The directional information is brought to the mho distance measurement from the mho
directional element as binary coded information to the input DIRCND. See Directional
impedance element for mho characteristic (ZDMRDIR ,21D) for information about the
mho directional element.
I jX
AB
ArgNegRes
ANSI07000111 V1 EN
Figure 120: 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 121. The
operation area in second quadrant is ArgNegRes+180°.
Operation occurs if 90≤β≤270 and 180° - ArgDir ≤φ ≤ ArgNegRes + 180°
35
ZPP
V
AB
f
I
AB
ArgDir
en07000111_ansi
1MRK505222-UUS C
Technical reference manual