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IEC06000592-2-en.vsd
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
1
1.5
2
2.5
3
3.5
Degree of series compensation [%]
In
c
re
a
se
i
n
p
o
we
r
tr
a
n
s
fe
r
Power transfer with constant angle difference
Degree of
compensation
Multiple of power over
a non-compensated line
IEC06000592 V2 EN-US
Figure 214: Increase in power transfer over a transmission line depending on degree of
series compensation
7.13.3.3
Voltage and current inversion
GUID-CB215C0F-F4FA-4646-9235-AE6DB0255E80 v1
Series capacitors influence the magnitude and the direction of fault currents in series
compensated networks. They consequently influence phase angles of voltages measured in
different points of series compensated networks and this performances of different
protection functions, which have their operation based on properties of measured voltage and
current phasors.
Voltage inversion
GUID-E649A7CB-9877-48F7-8AB3-25D5E8695673 v1
Figure
presents a part of series compensated line with reactance X
L1
between the IED
point and the fault in point F of series compensated line. The voltage measurement is
supposed to be on the bus side, so that series capacitor appears between the IED point and
fault on the protected line. Figure
presents the corresponding phasor diagrams for the
cases with bypassed and fully inserted series capacitor.
Voltage distribution on faulty lossless serial compensated line from fault point F to the bus is
linearly dependent on distance from the bus, if there is no capacitor included in scheme (as
shown in figure
). Voltage U
M
measured at the bus is equal to voltage drop
D
U
L
on the
faulty line and lags the current I
F
by 90 electrical degrees.
The situation changes with series capacitor included in circuit between the IED point and the
fault position. The fault current I
F
) is increased due to the series capacitor,
generally decreases total impedance between the sources and the fault. The reactive voltage
drop
D
U
L
on X
L1
line impedance leads the current by 90 degrees. Voltage drop
D
U
C
on series
capacitor lags the fault current by 90 degrees. Note that line impedance X
L1
could be divided
into two parts: one between the IED point and the capacitor and one between the capacitor
and the fault position. The resulting voltage U
M
in IED point is this way proportional to sum of
voltage drops on partial impedances between the IED point and the fault position F, as
presented by
(
)
1
=
×
-
M
F
L
C
U
I
j X
X
EQUATION1901 V1 EN-US
(Equation 384)
1MRK 505 343-UEN B
Section 7
Impedance protection
339
Application manual
Содержание Relion 670 series
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