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Current inversion
GUID-9F7FDF59-D0B4-4972-9CB0-B3D56DACA09E v1
Figure
presents part of a series compensated line with corresponding equivalent voltage
source. It is generally anticipated that fault current I
F
flows on non-compensated lines from
power source towards the fault F on the protected line. Series capacitor may change the
situation.
en06000607.vsd
~
Z<
X
S
X
L1
I
F
U
U
M
Source
Fault voltage
Pre -fault voltage
X
C
Source voltage
U’
M
With bypassed
capacitor
With inserted
capacitor
F
IEC06000607 V1 EN-US
Figure 217: Current inversion on series compensated line
The relative phase position of fault current I
F
compared to the source voltage U
S
depends in
general on the character of the resultant reactance between the source and the fault position.
Two possibilities appear:
1
1
0
0
-
+
>
-
+
<
S
C
L
S
C
L
X
X
X
X
X
X
EQUATION1935 V1 EN-US
(Equation 386)
The first case corresponds also to conditions on non compensated lines and in cases, when
the capacitor is bypassed either by spark gap or by the bypass switch, as shown in phasor
diagram in figure
. The resultant reactance is in this case of inductive nature and the fault
currents lags source voltage by 90 electrical degrees.
The resultant reactance is of capacitive nature in the second case. Fault current will for this
reason lead the source voltage by 90 electrical degrees, which means that reactive current will
flow from series compensated line to the system. The system conditions are in such case
presented by equation
1
>
+
C
S
L
X
X
X
EQUATION1936 V1 EN-US
(Equation 387)
1MRK 505 343-UEN B
Section 7
Impedance protection
341
Application manual
Содержание Relion 670 series
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