ABB RED615 Technical Manual page 334

Section 4
Protection functions
328
In case of the non-directional conductance criterion, the Conductance reverse
setting must be set to a smaller value than Conductance forward. If this rule is not
followed, a conflict situation is declared in the monitored data CONFLICT.
Operation is achieved when the measured admittance moves outside the
characteristic.
The combined overadmittance and overconductance criterion is applicable in
unearthed, high-resistance earthed and compensated networks or in systems where
the system earthing may temporarily change during normal operation from
compensated network to unearthed system.
Compared to the overadmittance criterion, the combined characteristic improves
sensitivity in high-resistance earthed and compensated networks. Compared to the
non-directional overconductance criterion, the combined characteristic enables the
protection to be applied also in unearthed systems.
Im(Yo)
OPERATE
Conductance reverse
Circle radius
Conductance forward
OPERATE
GUID-7AE09721-1428-4392-9142-A6D39FD4C287 V1 EN
Figure 166: Combined overadmittance and overconductance characteristic.
Left figure: classical origin-centered admittance circle combined
with two overconductance boundary lines. Right figure: admittance
circle is set off from the origin.
Combined overconductance and oversusceptance characteristic
The combined overconductance and oversusceptance criterion is enabled with the
Operation mode setting set to "Go, Bo".
By setting Directional mode to "Forward", the characteristic is a combination of
two boundary lines with the settings Conductance forward and Susceptance
forward. See Figure 167.
By setting Directional mode to "Non-directional", the characteristic is a
combination of four boundary lines with the settings Conductance forward,
Conductance reverse, Susceptance forward and Susceptance reverse. See
168.
OPERATE OPERATE
Conductance reverse
Re(Yo)
Circle susceptance
Circle radius
OPERATE OPERATE
1YHT530004D05 D
Im(Yo)
OPERATE
Conductance tilt Ang
Re(Yo)
Conductance forward
Circle conductance
OPERATE
Figure
615 series
Technical Manual