ABB RELION REX640 Technical Manual page 908

Section 4
Protection functions
902
Non-directional
Imp zone shape
Quadrilateral
Mho (circular)
Mho Dir line
Offset Dir line
Bullet (combi)
GUID-179A8D80-55DB-4CEF-9931-68C06F53CA0B V1 EN
Figure 495: Possible combinations of Directional mode Znx and zone
characteristics settings. Pol. in the figure means that the shape of the
characteristic is affected by the selected polarization method of the
mho circle, Pol quantity zone = "Cross pol", "Pos. seq. volt.", "Self
pol").
Bullet combi characteristic
If the impedance zone shape equals "Bullet (combi)", the distance protection has a
tripping characteristic which is a combination of the quadrilateral and mho. All
settings relevant to the quadrilateral and mho are applicable. The shape of the "Bullet
(combi)" characteristic is affected by the selected polarization method of the mho
circle (Pol quantity zone = "Cross pol", "Pos. seq. volt.", "Self pol").
The directionality of the "Bullet (combi)" characteristic is defined by the directional
lines when Directional mode Znx is "Forward" or "Reverse". For directional "Bullet
(combi)" characteristic, the quadrilateral resistance does not reach negative (positive)
values for "Forward" ("Reverse") direction (see
Directional mode Znx
Forward
X X
R
X X
R
X
X
R
X
X
R
X X
R
Pol. = polarization method affects (mho)zone shape
Figure
1MRS759142 C
Reverse
X
R R
Pol. Pol.
X
R R
Pol. Pol.
X
R R
X
R R
Pol. Pol.
X
R R
496).
REX640
Technical Manual