ABB RELION RET670, Applications Manual

Page: 215 / 1016

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 83: 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
84 . The
power transfer on the transmission line is given by the equation 55 :
( ) ( )
( )
A B A B
Line C Line C
V V sin V V sin
P
X X X 1 K
d d
× × × ×
= =
- × -
EQUATION1994-ANSI V1 EN-US
(Equation 55)
The compensation degree K
c
is defined as equation
A B
-jX
C
P
A
Q
A
P
B
Q
B
V
A
V
B
V
+jX
L
V
A
V
B
en06000590_ansi.vsd
D
d
ANSI06000590 V1 EN-US
Figure 84: 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
85 . Practical compensation degree runs
1MRK 504 163-UUS A
Section 8
Impedance protection
Transformer protection RET670 2.2 ANSI 209
Application manual