ABB Relion REG670, Applications Manual

Page: 236 / 780

8.3.3.2 Increase in power transfer
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
108 .
The power transfer on the transmission line is given by the equation 107 :
( ) ( )
( )
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
(Equation 107)
The compensation degree K
c
is defined as equation 105
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
Figure 108: 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
109 . Practical compensation degree runs
from 20 to 70 percent. Transmission capability increases of more than two times can
be obtained in practice.
IEC06000592-2-en.vsd
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
1
1.5
2
2.5
3
3.5
Degree of series compensation [%]
In
c
re
a
se
i
n
p
o
we
r
tr
a
n
s
fe
r
Power transfer with constant angle difference
Degree of
compensation
Multiple of power over
a non-compensated line
IEC06000592 V2 EN
Figure 109: Increase in power transfer over a transmission line depending on
degree of series compensation
8.3.3.3 Voltage and current inversion
Series capacitors influence the magnitude and the direction of fault currents in series
compensated networks. They consequently influence phase angles of voltages
measured in different points of series compensated networks and this performances of
Section 8
1MRK 502 071-UEN -
Impedance protection
230 Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual