ABB Relion 670 Series Technical Reference Manual page 444

Section 7
Current protection
7.6.2
7.6.2.1
438
Principle of operation
Function inputs
The function is using phasors of the residual current and voltage. Group signals I3P
and V3P containing phasors of residual current and voltage is taken from pre-processor
blocks.
The sensitive directional ground fault protection has the following sub-functions
included:
Directional residual current protection measuring 3I
φ is defined as the angle between the residual current 3I
jRCADir
Vref = -3V e , that is -3V
0
(φ=ang(3I )-ang(V ) ). RCADir is normally set equal to 0 in a high impedance
0 ref
grounded network with a neutral point resistor as the active current component is
appearing out on the faulted feeder only. RCADir is set equal to -90° in an isolated
network as all currents are mainly capacitive. The function operates when 3I
gets larger than the set value.
ANSI06000648 V1 EN
Figure 218: RCADir set to 0°
rotated by the set characteristic angle RCADir
0
V
RCA = 0°, ROA = 90°
ref
3I
0
) - ang(3V
= ang(3I
0 ref
3I cos
0
en06000648_ansi.vsd
1MRK505222-UUS C
·cos φ
0
and the reference voltage.
0
)
-3V =V
0 ref
Technical reference manual
·cos φ
0