Description of Operation
GARD 8000 Distance Relay
RFL Electronics Inc.
9.12.3
NEGATIVE SEQUENCE DIRECTIONAL UNIT
The operation of the negative sequence directional unit is based on calculated negative sequence
current and voltage.
The operating quantity is I2.
The polarizing quantity is –V2+I2 x set compensation factor
∠
(set angle).
The last term in the polarizing quantity is intended to increase the available polarizing quantity by
boosting the magnitude.
The following table gives the operating criteria.
Table 9-17. Directional Negative Sequence Element
Directional Negative Sequence Element
Operating
phasor
Polarizing phasor
Criteria
I2
-V2+I2 x COMP
∠
ANG_67Q
-(90
°
+ANG_67Q)
≤
[arg(OP)-arg(POL)]
≤
(90-ANG_67Q)
The minimum polarizing quantity is settable 0.05 – 10 V. The sensitivity of the operating quantity is
0.02 x IN (0.1 A for a 5A relay). If the magnitudes are below these thresholds, 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 setting.
Figure 9-54. Negative Sequence Network for a Forward Fault
For a forward fault, -V2 = ZA2
⋅
(-I2) where ZA2 is the negative sequence impedance of the local
source. Consequently, the angle between –V2 and I2 will be the angle of this impedance. ANG_67Q
should be set to
∠
ZA2.
9.12.4
ZONE 2 TORQUE CONTROL
Zone 2 phase and ground elements can by used for torque control of the overcurrent units in the same
way as the directional units.
August 1, 2009
9-60
973.334.3100
