ABB RELION REX640 Technical Manual page 476

Section 4
Protection functions
470
Forward directional oversusceptance characteristic
The forward directional oversusceptance criterion is enabled with the Operation mode
setting set to "Bo" and Directional mode to "Forward". The characteristic is defined
by one oversusceptance boundary line with the Susceptance forward setting. For the
sake of application flexibility, the boundary line can be tilted by the angle defined with
the Susceptance tilt Ang setting. By default, the tilt angle is zero degrees, that is, the
boundary line is a horizontal line in the admittance plane. A positive tilt value rotates
the boundary line counterclockwise from the horizontal axis.
Operation is achieved when the measured admittance moves over the boundary line.
The forward directional oversusceptance criterion is applicable in
unearthed networks. It must not be applied to compensated networks.
GUID-0997B962-6771-40D2-A300-AD957A924FB8 V1 EN
Figure 255: Forward directional oversusceptance characteristic. Left figure:
classical forward directional oversusceptance criterion. Middle
figure: characteristic is tilted with negative tilt angle. Right figure:
characteristic is tilted with positive tilt angle.
Combined overadmittance and overconductance characteristic
The combined overadmittance and overconductance criterion is enabled with the
Operation mode setting set to "Yo, Go" and Directional mode to "Non-directional".
The characteristic is a combination of a circle with the radius defined with the Circle
radius setting and two overconductance boundary lines with the settings Conductance
forward and Conductance reverse. For the sake of application flexibility, the midpoint
of the circle can be moved from the origin with the Circle conductance and Circle
susceptance settings. Also the boundary lines can be tilted by the angle defined with
the Conductance tilt Ang setting. By default, the Circle conductance and Circle
susceptance are 0.0 mS and Conductance tilt Ang equals zero degrees, that is, the
characteristic is a combination of an origin-centered circle with two vertical
overconductance boundary lines. A positive tilt value for the Conductance tilt Ang
setting rotates boundary lines counterclockwise from the vertical axis.
In case of the non-directional conductance criterion, the Conductance reverse setting
must be set to a smaller value than Conductance forward.
1MRS759142 C
REX640
Technical Manual