ABB REG670 Applications Manual page 235

1MRK 502 071-UEN -
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
drop is lower and at the same time, the voltage drop on the series capacitor is lower.
When the loading increases and the voltage drop become larger, the contribution of
the series capacitor increases and therefore the system voltage at the receiving line end
can be regulated.
Series compensation also extends the region of voltage stability by reducing the
reactance of the line and consequently the SC is valuable for prevention of voltage
collapse. Figure 107 presents the voltage dependence at receiving bus B (as shown in
figure 106) on line loading and compensation degree K
to equation 105. The effect of series compensation is in this particular case obvious
and self explanatory.
X
=
K C
C
X
Line
EQUATION1895 V1 EN
A typical 500 km long 500 kV line is considered with source impedance
=
Z 0
SA 1
EQUATION1896 V1 EN
A
Z
SA1
~
E
A
Seires
capacitor
IEC06000585 V1 EN
Figure 106: A simple radial power system
500
400
300
200
100
0 200 400 600 800
IEC06000586 V1 EN
Figure 107: Voltage profile for a simple radial power line with 0, 30, 50 and 70%
of compensation
B
Power line
Load
en06000585.vsd
U
limit
1000 1200 1400 1600 1800
P[MW]
en06000586.vsd
Section 8
Impedance protection
, which is defined according
C
(Equation 105)
(Equation 106)
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