at three phase fault and therefore the calculation need only to be performed for three phase
faults.
The compensation degree in earth return path is different than in phases. It is for this reason
possible to calculate a compensation degree separately for the phase-to-phase and three-
phase faults on one side and for the single phase-to-earth fault loops on the other side.
Different settings of the reach for the ph-ph faults and ph-E loops makes it possible to
minimise the necessary decrease of the reach for different types of faults.
Reactive Reach
jX
R
X
C
Z
S
X
1
R
V
R
FW
R
RV
Z
S
en06000584-2.vsd
X
LLOC
X
1
F
W
X
C
X
line
- X
C
IEC06000584 V2 EN-US
Figure 236: Measured impedance at voltage inversion
Forward direction:
Where
X
LLoc
equals line reactance up to the series capacitor(in the picture approximate
33% of XLine)
X1
Fw
is set to (XLine-X
C
) · p/100.
X1
Rv
= max( 1.5 x (X
C
-X
LLOC
C); X1
Fw
is defined according to figure
When the calculation of
X1Fwgives a negative value the zone 1 must be
permanently blocked.
For protection on non compensated lines facing series capacitor on next line. The setting is
thus:
Section 7
1MRK 505 343-UEN B
Impedance protection
356
Application manual
Содержание Relion 670 series
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