Capacitive
Inductive
200
400
600
800
1000
200
400
600
Q
(Mvar)
500 1000 1500
Power flow
(MW)
(T.L.)
(S.C.)
(T.L.
+
S.C.)
Transmission
Line
Series
Compensation
500 kV
500 km
k = 50 %
en06000589.vsd
IEC06000589 V1 EN-US
Figure 70: Self-regulating effect of reactive power balance
Increase in power transfer
SEMOD168320-45 v2
The increase in power transfer capability as a function of the degree of
compensation for a transmission line can be explained by studying the circuit
shown in figure 71. The power transfer on the transmission line is given by the
equation
47:
( ) ( )
( )
sin sin
1
d d
× × × ×
= =
- × -
A B A B
Line C Line C
U U U U
P
X X X K
EQUATION1897 V1 EN-US (Equation 47)
The compensation degree K
c
is defined as equation
A B
-jX C
P
A
Q
A
P
B
Q
B
U
A
U
B
U
+jXL
U
A
U
B
d
D
en06000590.vsd
IEC06000590 V1 EN-US
Figure 71: Transmission line with series capacitor
The effect on the power transfer when considering a constant angle difference (δ)
between the line ends is illustrated in figure 72. Practical compensation degree runs
from 20 to 70 percent. Transmission capability increases of more than two times
can be obtained in practice.
1MRK 506 369-UEN B Section 8
Impedance protection
Line distance protection REL670 2.2 IEC 165
Application manual
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