A typical 500 km long 500 kV line is considered with source impedance
EQUATION1896 V1 EN (Equation 49)
~
E
A
Z
SA1
Power line
A B
Seires
capacitor
Load
en06000585.vsd
IEC06000585 V1 EN
Figure 68: A simple radial power system
en06000586_ansi.vsd
0 200 400 600 800 1000 1200 1400 1600 1800
100
200
300
400
500
P[MW]
V
[
k
V
]
V
limit
P
0
P
3
0
P
5
0
P
7
0
ANSI06000586 V1 EN
Figure 69: Voltage profile for a simple radial power line with 0, 30, 50 and 70% of
compensation
Increased power transfer capability by raising the first swing stability limit
Consider the simple one-machine and infinite bus system shown in figure 70.
en06000587.vsd
~
E
A
Z
SA1
A B
P
Mech
+jX
Line
-jX
C
System
IEC06000587 V1 EN
Figure 70: One machine and infinite bus system
The equal-areas criterion is used to show the effectiveness of a series capacitor for
improvement of first swing transient stability (as shown in figure
71).
In steady state, the mechanical input power to the generator (P
Mech
) is equal to the
electrical output power from the generator (P
E
) and the generator angle is d
0
. If a 3-phase
fault occurs at a point near the machine, the electrical output of the generator reduces to
zero. This means that the speed of the generator increases and the angle difference
Section 8 1MRK 506 369-UUS -
Impedance protection
174 Line distance protection REL670 2.2 ANSI
Application manual
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