ABB RELION REX640 Technical Manual page 978

Protection functions
The directional offset mho is explicitly defined by the reach settings and is thus
fixed in the impedance plane. The polarization method does not expand this circle
even for directional mode. However, directional lines criteria are defined using
polarized signals.
X1 zone x
Figure 552: Tripping characteristic for phase-to-phase or three-phase impedance
measuring elements if Impedance Chr PP Zn is "Mho (circular)" and Directional
mode Znx is "Non-directional". On the left, Impedance mode Zn is "Rectangular". On
the right, Impedance mode Zn is "Polar".
-
X1 reverse zone x
X1 zone x
Figure 553: Tripping characteristic for phase-to-earth impedance measuring
elements if Impedance Chr GND Zn is "Mho (circular)" and Directional mode Znx
is "Non-directional". On the left, Impedance mode Zn is "Rectangular". On the right,
Impedance mode Zn is "Polar".
Adding of directional lines into circular mho characteristic
Directional lines which are always included in the directional quadrilateral
characteristic can also be included in the mho characteristics to secure the
directionality or to transform the non-directional mho characteristics into a
directional one.
Directional lines with mho are available only when the zone is set to directional, that
Directional mode Znx is "Forward" or "Reverse".
is,
The directionality of the directional mho characteristic is secured with directional
lines by setting
The directional mho characteristic can also be created by adding directional lines in
978
X
α
R1 zone x R
α
- X1 reverse zone x
⋅
(2 X1 zone x + X0 zone x)/3
* (2 X1 zone x + X0 zone x)/3
⋅
-X1 reverse zone x
* (2 R1 zone x + R0 zone x)/3
X1 zone x
Impedance Chr Gnd Zn and Impedance Chr PP Zn to "Mho Dir line".
X
α
R
⋅
(2 R1 zone x + R0 zone x)/3
α
1MRS759142 F
X
R
X
α
α
Technical Manual
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REX640