ABB REL650 series Technical Manual page 243

1MRK 506 335-UUS A
7.7.7.2
Technical manual
Directional residual current protection measuring 3I
φ is defined as the angle between the residual current 3I
jRCADir
-3V e , that is -3V
0
ang(V ) ). RCADir is normally set equal to 0 in a high impedance grounded network with
ref
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
ANSI06000648 V1 EN
Figure 106: RCADir set to 0°
rotated by the set characteristic angle RCADir (φ=ang(3I
0
·cos φ gets larger than the set value.
0
V
RCA = 0°, ROA = 90°
ref
3I
0
) - ang(3V
= ang(3I
0 ref
3I cos
0
en06000648_ansi.vsd
Current protection
·cos φ
0
and the reference voltage. Vref =
0
)
-3V =V
0 ref
Section 7
)-
0
237