ABB 615 series Technical Manual page 396

Section 4
Protection functions
390
Im(Yo)
TRIP TRIP
Susceptance forward
Re(Yo)
Re(Yo)
GUID-3E09080E-9063-4D3B-A29E-3AA34EB03812 V1 EN
Figure 184: 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.
Operation is achieved when the measured admittance moves outside the characteristic.
The combined overadmittance and overconductance criterion is applicable in
ungrounded, high-resistance grounded and compensated networks or in systems where
the system grounding may temporarily change during normal operation from
compensated network to ungrounded system.
Compared to the overadmittance criterion, the combined characteristic improves
sensitivity in high-resistance grounded and compensated networks. Compared to the non-
directional overconductance criterion, the combined characteristic enables the protection
to be applied also in ungrounded systems.
Im(Yo)
TRIP TRIP
Susceptance tilt Ang <0
Susceptance forward
Re(Yo)
Re(Yo)
1MAC059074-MB A
Im(Yo)
TRIP TRIP
Susceptance tilt Ang >0
Susceptance forward
Re(Yo)
615 series ANSI
Technical Manual