Distance Relay Setting Examples
GARD 8000 Distance Relay
RFL Electronics Inc.
Description Range
Units
Step
Actual
51G-3 Torque Control Type
Selection to use directional element or Zone 2 for torque control of
the ground timeovercurrent element, step 3
67G
67Q
Z2G -
1 67N
51G-3 Torque Control Direction
Directional control of ground timeovercurrent element, step 3
NO
Forward
Reverse - 1 NO
8.2.15
GROUND DIRECTIONAL SETTINGS
The operation of the ground directional unit is based on zero sequence quantities. The operating
quantity is the zero sequence current and the polarizing quantity is the zero sequence voltage.
The operating quantity is I0. The polarizing quantity is –V0 + (I0 x set compensation factor)@
(ANG_67G).
The compensation factor in the polarizing quantity formula is intended to increase the available
polarizing quantity by boosting the magnitude, when required. The majority of applications has this
factor set to 0.
The minimum polarizing voltage (67G Minimum voltage) is settable 0.05 – 10 V. If the magnitudes
are below the set threshold, the unit will not be able to make a directional determination and the
overcurrent units are blocked or allowed to issue a non-directional trip as selected by the setting “Loss
of polarization blocking.” With this set to “No” the elements are blocked. With this set to “Yes” the
elements are allowed to trip non-directional.
As the 67DCB scheme will be defeated without directional discrimination, the “Loss of polarization
blocking” should be set to “Yes”
in case
there is a possibility of the polarization voltage dropping
below the set threshold for the actual application.
Recommended setting for Minimum voltage is 1 V and for Voltage Compensation 0.
The 67G Characteristic angle should be set equal to the local zero sequence source impedance angle
(Z0SL). In our example Z0SL = 86 degrees.
August 1, 2009
8-36
973.334.3100
