6.5.7.2 Directional residual current protection measuring 3I
0
·cos φ
φ is defined as the angle between the residual current 3I
0
and the reference voltage. Vref =
-3V
0
e
jRCADir
, that is -3V
0
rotated by the set characteristic angle RCADir (φ=ang(3I
0
)-
ang(V
ref
) ). RCADir is normally set equal to 0 in a high impedance 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
0
·cos φ gets larger than the set value.
-3V
0
=V
ref
3I
0
RCA = 0°, ROA = 90°
= ang(3I
0
) - ang(3V
ref
)
3I
0
cos
en06000648_ansi.vsd
V
ref
ANSI06000648 V1 EN
Figure 44: RCADir set to 0°
Section 6 1MRK 511 287-UUS A
Current protection
120
Technical manual
To Next Page
Loading...
