ABB REL670 2.2 IEC, Applications Manual

Page: 171 / 908

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
+jX
L
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