The effect on the power transfer when considering a constant angle difference (δ) between
the line ends is illustrated in figure 74. Practical compensation degree runs from 20 to 70
percent. Transmission capability increases of more than two times can be obtained in
practice.
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 [%]
Increase in power transfer
Power transfer with constant angle difference
Degree of
compensation
Multiple of power over
a non-compensated line
IEC06000592 V2 EN
Figure 74: Increase in power transfer over a transmission line depending on degree
of series compensation
Active load sharing between parallel circuits and loss reduction
A series capacitor can be used to control the distribution of active power between parallel
transmission circuits. The compensation of transmission lines with sufficient thermal
capacity can relieve the possible overloading of other parallel lines. This distribution is
governed by the reactance, while the losses are determined by the resistance. A properly
designed series compensation system can considerably reduce the total transmission
system losses, as shown in figure
75.
en06000593.vsd
R
L1jXL1
-jX
C
Line 1
jX
L2
R
L2
Line 2
IEC06000593 V1 EN
Figure 75: Two parallel lines with series capacitor for optimized load sharing and
loss reduction
To minimize the losses, the series capacitor must be installed in the transmission line with
the lower resistance. The size of the series capacitor that minimizes the total losses is given
the following expression:
1MRK 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 177
Application manual
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