ABB REL670 2.2 IEC - Impact of Series Compensation on Protective IED of Adjacent Lines

8.13.3.4 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.vsd
~
~
F
B
E
B
E
A
Z
SA
U
A
A
Z
LA
I
A
U
D
D
Z
LB
I
B
U
B
Z
SB
Z
LF
I
F
-jX
C
IEC06000616 V1 EN-US
Figure 208: Voltage inversion in series compensated network due to fault
current infeed
Voltage at the B bus (as shown in figure 208) is calculated for the loss-less system
according to the equation below.
U U I jX I I j X X I jX
B D
B
LB
A B
LF C
B
LB
= + ⋅ = +
( )
⋅ −
( )
+ ⋅
EQUATION1911 V2 EN-US (Equation 366)
Further development of equation 366 gives the following expressions:
U jI X
I
I
X X
B
B LB
A
B
LF C
= ⋅ + +








⋅ −
( )








1
EQUATION1912 V2 EN-US
(Equation 367)
( )
0
1
= = +
+
LB
C B LF
A
B
X
X U X
I
I
EQUATION1913 V1 EN-US (Equation 368)
Equation 367 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 equation 368 indicates the deepness of the network to which it
will feel the influence of series compensation through the effect of voltage
inversion.
It is also obvious that the position of series capacitor on compensated line
influences in great extent the deepness of voltage inversion in adjacent system.
Line impedance X
LF
between D bus and the fault becomes equal to zero, if the
capacitor is installed near the bus and the fault appears just behind the capacitor.
This may cause the phenomenon of voltage inversion to be expanded very deep
Section 8 1MRK 506 369-UEN B
Impedance protection
384 Line distance protection REL670 2.2 IEC
Application manual