ABB REL670 2.2 IEC, Applications Manual

Page: 381 / 908

~
E
A
Z
SA1 Power line
A B
Seires
capacitor
Load
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IEC06000585 V1 EN-US
Figure 195: A simple radial power system
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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-US
Figure 196: Voltage profile for a simple radial power line with 0, 30, 50 and
70% of compensation
8.13.3.2 Increase in power transfer
GUID-C9163D4E-CC2B-4645-B2AC-2C8A3FE3D337 v3
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
197 . The power transfer on the transmission line is given by the
equation 360 :
( ) ( )
( )
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-US
(Equation 360)
The compensation degree K
c
is defined as equation
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
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IEC06000590 V1 EN-US
Figure 197: 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
198 . Practical compensation degree
runs from 20 to 70 percent. Transmission capability increases of more than two
times can be obtained in practice.
1MRK 506 369-UEN B
Section 8
Impedance protection
Line distance protection REL670 2.2 IEC 375
Application manual