ABB RELION Series, Техническое руководство

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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.
GUID-7AE09721-1428-4392-9142-A6D39FD4C287 V2 EN
Figure 176: 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 177 .
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 Figure 178 .
For the sake of application flexibility, the boundary lines can be tilted by the angle
defined with the
Conductance tilt Ang and Susceptance tilt Ang settings. By default,
the tilt angles are zero degrees, that is, the boundary lines are straight lines in the
admittance plane. A positive
Conductance tilt Ang value rotates the overconductance
1MRS758755 A
Section 4
Protection functions
REC615 and RER615 343
Technical Manual