ABB REC650 - Directional Residual Current Protection Measuring 3 I ·Cos

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.
Uref = -3U
0
e
jRCADir
, that is -3U
0
rotated by the set characteristic angle RCADir
(φ=ang(3I
0
)-ang(U
ref
) ). RCADir is normally set equal to 0 in a high impedance
earthed 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.
= =
 
0 , 0RCADir ROADir
0
3I
ϕ = −
0 ref
ang(3I ) ang(3U )
− =
0 ref
3U U
0
3I cos
⋅
ϕ
IEC06000648-3-en.vsd
IEC06000648 V3 EN
Figure 44: RCADir set to 0°
IEC06000649_3_en.vsd
ref
U
= − =
 
90 , 90RCADir ROADir
0
3I
0
3 ⋅ ϕI cos
ϕ = −
0
(3 ) ( )
ref
ang I ang U
−
0
3U
IEC06000649 V3 EN
Figure 45: RCADir set to -90°
Section 6 1MRK 511 287-UEN A
Current protection
114
Technical manual