8.6.6
Monitored data
Table 192:
SDEPSDE Monitored data
Name
Type
Values (Range)
Unit
Description
INCOSPHI
REAL
-
A
Magnitude of residual
current along the
polarizing quantity
3I0cos(Fi-RCA)
IN
REAL
-
A
Measured magnitude of
the residual current 3I0
UN
REAL
-
kV
Measured magnitude of
the residual voltage 3U0
SN
REAL
-
MVA
Measured magnitude of
residual power
3I03U0cos(Fi-RCA)
ANG FI-RCA
REAL
-
deg
Angle between 3U0 and
3I0 minus RCA (Fi-RCA)
8.6.7
Operation principle
8.6.7.1
Function inputs
The function is using phasors of the residual current and voltage. Group signals I3P
and U3P containing phasors of residual current and voltage are taken from pre-
processor blocks.
The sensitive directional earth fault protection has the following sub-functions
included:
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 (|
φ=ang(3I
0
)-ang(U
ref
)|). The reference voltage (Uref) is the polarizing quantity which
is used for directionality and is defined as Uref = -3U
0
e
—jRCADir
, that is -3U
0
inversely
rotated by the set characteristic angle
RCADir
.
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.
1MRK502052-UEN B
Section 8
Current protection
393
Technical manual
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