•
Series capacitor becomes nearly completely bridged by MOV when the line
current becomes higher than 10-times the protective current level (I
£
10· k
p
· I
NC
).
8.3.3.4
Impact of series compensation on protective IED of adjacent lines
GUID-DA1DBB5B-0AFD-49F4-87C7-0E8AB5006051 v2
Voltage inversion is not characteristic for the buses and IED points closest to the series
compensated line only. It can spread also deeper into the network and this way
influences the selection of protection devices (mostly distance IEDs) on remote ends of
lines adjacent to the series compensated circuit, and sometimes even deeper in the
network.
en06000616_ansi.vsd
~
~
Z
LF
Z
LA
Z
LB
E
A
E
B
V
A
V
B
V
D
I
B
I
A
I
F
-jX
C
F
A
B
D
Z
SA
Z
SB
ANSI06000616 V1 EN-US
Figure 119:
Voltage inversion in series compensated network due to fault current
infeed
Voltage at the B bus (as shown in figure
) is calculated for the loss-less system
according to the equation below.
(
) (
)
=
+
×
=
+
×
-
+
×
B
D
B
LB
A
B
LF
C
B
LB
V
V
I
jX
I
I
j X
X
I
jX
EQUATION1998-ANSI V1 EN-US
(Equation 108)
Further development of equation
gives the following expressions:
(
)
1
=
×
+
+
×
-
é
ù
æ
ö
ê
ç
÷
ú
è
ø
ë
û
A
B
B
LB
LF
C
B
I
V
jI
X
X
X
I
EQUATION1999-ANSI V1 EN-US
(Equation 109)
(
)
0
1
=
=
+
+
LB
C
B
LF
A
B
X
X
V
X
I
I
EQUATION2000-ANSI V1 EN-US
(Equation 110)
Equation
indicates the fact that the infeed current I
A
increases the apparent value
of capacitive reactance in system: bigger the infeed of fault current, bigger the apparent
series capacitor in a complete series compensated network. It is possible to say that
Section 8
1MRK 502 071-UUS A
Impedance protection
256
Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062
Application manual
Summary of Contents for RELION 670 SERIES REG670
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