Manual XRI1-ER
Woodward
TD_XRI1-ER_12.03, Rev. C
15
Figure 4.3: Phase position between the residual voltage and zero sequence current for faulted and non-faulted lines in
case of isolated systems (sin
φ)
U
E
- residual voltage
I
E
- zero sequence current
I
C
- capacitive component of zero sequence current
I
W
- resistive component of zero sequence current
By calculating the reactive current component (sin
φ adjustment) and then comparing the phase angle in rela-
tion to the residual voltage U
E
, the ER/XR-relay type determines whether the line to be protected is earth-
faulted.
On non-earth-faulted lines, the capacitive component I
c(a)
of the total current precedes the residual voltage by an
angle of 90°. In case of a faulty line the capacity current I
C(b)
lags behind the residual voltage at 90°.
