ABB Relion REG670, Applications Manual

Page: 235 / 780

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
C
, which is defined according
to equation 105 . The effect of series compensation is in this particular case obvious
and self explanatory.
=
C
C
Line
X
K
X
EQUATION1895 V1 EN
(Equation 105)
A typical 500 km long 500 kV line is considered with source impedance
1
0
=
SA
Z
EQUATION1896 V1 EN
(Equation 106)
~
E
A
Z
SA1
Power line
A B
Seires
capacitor
Load
en06000585.vsd
IEC06000585 V1 EN
Figure 106: A simple radial power system
en06000586.vsd
0 200 400 600 800 1000 1200 1400 1600 1800
100
200
300
400
500
P[MW]
U
[k
V
]
U
limit
P
0
P
3
0
P
5
0
P
7
0
IEC06000586 V1 EN
Figure 107: Voltage profile for a simple radial power line with 0, 30, 50 and 70%
of compensation
1MRK 502 071-UEN -
Section 8
Impedance protection
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062 229
Application manual