bus depending on type of overvoltage protection used on capacitor bank (spark gap
or MOV) and SC location on protected power line.
en06000612.vsd
~
E
A
0%
33 %
50 %
66 %
K
C
=
80% 33% 33 %50 %
Z<
100 %
80 %
IEC06000612 V1 EN-US
Figure 86: Typical locations of capacitor banks on series compensated line
Implementation of spark gaps for capacitor overvoltage protection makes the
picture relatively simple, because they either flash over or not. The apparent
impedance corresponds to the impedance of non-compensated line, as shown in
figure 87 case K
C
= 0%.
en06000613.vsd
j
X
R
KC = 0%
KC = 80%
LOC = 0%
KC = 50%
LOC = 50%
j
X
j
X
R R
KC = 2 x 33%
LOC = 33%, 66%
KC = 80%
LOC = 100%
j
X
j
X
R R
IEC06000613 V1 EN-US
Figure 87: Apparent impedances seen by distance IED for different SC
locations and spark gaps used for overvoltage protection
Section 8 1MRK 506 369-UEN B
Impedance protection
178 Line distance protection REL670 2.2 IEC
Application manual
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