Siemens siprotec 7SD5

2 Functions
60
7SD5 Manual
C53000-G1176-C169-1
For conversion of primary values to secondary values the following applies in general:
Likewise, the following goes for the reactance setting of a line:
where
N
CT
= Current transformer ratio
N
VT
= Transformation ratio of voltage transformer
The following applies for the capacitance per distance unit:
Calculation Example:
110 kV overhead line 150 mm
2
as above
R'
1
= 0.19 Ω/km
X'
1
= 0.42 Ω/km
C' = 0.008 µF/km
Current Transformer 600 A / 1 A
Voltage transformer 110 kV / 0.1 kV
The secondary per distance unit reactance is therefore:
In address 1111 the setting x' = 0.229 Ω/km is entered.
The secondary per distance unit capacitance is therefore:
In address 1112 the setting c' = 0.015 µF/km is entered.
Earth Impedance
(Residual) Com-
pensation
Matching of the earth to line impedance is an essential prerequisite for the accurate
measurement of the fault distance (distance protection, fault locator) during earth
faults. This compensation is either achieved by entering the resistance ratio R
E
/R
L
and
the reactance ratio X
E
/X
L
or by entry of the complex earth (residual) compensation
factor K
0
. Which of these two entry options applies was determined by the setting in
address 237 Format Z0/Z1 (refer to Section 2.1.2.1). Only the addresses applicable
for this setting will be displayed.
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