performances for the same network with and without series capacitor. Possible effects of
spark gap flashing or MOV conducting are neglected. The time dependence of fault currents
and the difference between them are of interest.
en06000609.vsd
~
e
G
(t)
i
L
(t)
R
L
jX
L
-jX
C
F
IEC06000609 V1 EN-US
Figure 98: Simplified equivalent scheme of SC network during fault conditions
We consider the instantaneous value of generator voltage following the sine wave according
(
)
sin
w
l
=
×
× +
G
G
e
E
t
EQUATION1904 V1 EN-US
(Equation 74)
The basic loop differential equation describing the circuit in figure
without series capacitor
is presented by equation
(
)
sin
w
l
×
+
× =
×
× +
L
L
L
L
G
di
L
R i
E
t
dt
EQUATION1905 V1 EN-US
(Equation 75)
The solution over line current is presented by group of equations
(
)
(
)
(
)
(
)
0
2
2
sin
sin
w
l j
l j
w
w
j
- ×
=
é
ù
=
×
× + -
+
-
×
-
×
ê
ú
ë
û
=
+
×
æ
ö
×
=
ç
÷
è
ø
L
L
R
t
L
G
G
L
L t
L
L
L
L
E
E
i
t
I
e
Z
Z
Z
R
L
L
atg
R
EQUATION1906 V1 EN-US
(Equation 76)
The line fault current consists of two components:
•
The steady-state component which magnitude depends on generator voltage and
absolute value of impedance included in the circuit
•
The transient DC component, which magnitude depends on the fault incident angle
decays with the circuit time constant
[ ]
L
L
L R s
EQUATION1907 V1 EN-US
(Equation 77)
The basic loop differential equation describing the circuit in figure
with series capacitor is
presented by equation
(
)
2
2
1
( )
cos
w
w
l
×
+
×
+
=
× ×
× +
l
L
L
L
L
G
L
d i
di
L
R
i t
E
t
dt
dt
C
EQUATION1908 V1 EN-US
(Equation 78)
1MRK 505 343-UEN B
Section 7
Impedance protection
167
Application manual
Содержание Relion 670 series
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