Siemens siprotec 7SA522, User Manual

Page: 169 / 628

Functions
6-21
7SA522 Manual
C53000-G1176-C119-2
When determining the angle, the quadrant of the result must be considered. The fol-
lowing table indicates the quadrant and range of the angle which is determined by the
signs of the calculated real and imaginary part of K
0
.
In this example the following result is obtained:
The magnitude and angle of the earth impedance (residual) compensation factors set-
ting for the first zone Z1 and the remaining zones of the distance protection may be
different. This allows to set the exact values for the protected line, while at the same
time the setting for the back-up zones may be a close approximate even when the fol-
lowing lines have substantially different earth impedance ratios (e.g. cable after an
overhead line). Accordingly, the settings for the address
.=
and
$QJOH.=
are determined with the data of the protected line while the addresses
.!=
and
$QJOH,.!=
apply to the remaining zones Z1B
and Z2 up to Z5 (as seen from the relay location).
Parallel Line Mutual
Impedance If the device is applied to a double circuit line (parallel lines) and parallel line compen-
sation for the distance and/or fault location function is used, the mutual coupling of the
two lines must be considered. A prerequisite for this is that the earth (residual) current
of the parallel line has been connected to the measuring input
I
4
of the device and that
this was configured with the power system data (Section 6.1.1) by setting the appro-
priate parameters.
The coupling factors may be determined using the following equations:
Table 6-1 Quadrants and range of the angle of K
0
Real part
Imaginary
part
tan
ϕ
(K0) Quadrant/Range
Rules for calculation
+ + + I 0° ... +90° arctan(| Im |/| Re |)
+ – – IV –90° ... 0° –arctan(| Im |/| Re |)
– – +
III
–90° ... –180° arctan(|
Im
|/|
Re
|) – 180°
ϕ
K
0
( )
arc tan
1.263
0.102
---------------
 
 
180°
–
94.6°
– = =
Note:
If a combination of values is set which is not recognized by the device, it operates with
preset values K
0
= 1·e
0°
. The following event locks
appears:
„
'LV(UURU.!=
“
or “
'LV(UURU.=
“.