ABB RELION REX640 Technical Manual page 474

Section 4
Protection functions
468
GUID-5F36C6E5-9310-4E33-8CD9-16DB4ABDAEDB V1 EN
Figure 252: Overadmittance characteristic. Left figure: classical origin-centered
admittance circle. Right figure: admittance circle is set off from the
origin.
Non-directional overconductance characteristic
The non-directional overconductance criterion is enabled with the Operation mode
setting set to "Go" and Directional mode to "Non-directional". The characteristic is
defined with two overconductance boundary lines with the Conductance forward and
Conductance reverse settings. For the sake of application flexibility, the boundary
lines can be tilted by the angle defined with the Conductance tilt Ang setting. By
default, the tilt angle is zero degrees, that is, the boundary line is a vertical line in the
admittance plane. A positive tilt value rotates the boundary line counterclockwise
from the vertical axis.
In case of non-directional conductance criterion, the Conductance reverse setting
must be set to a smaller value than Conductance forward.
Operation is achieved when the measured admittance moves over either of the
boundary lines.
The non-directional overconductance criterion is applicable in high-
resistance earthed and compensated networks. It must not be applied
in unearthed networks.
1MRS759142 C
REX640
Technical Manual