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Likewise, the following goes for the reactance setting of a line:
where
N
CT
N
VT
The following applies for the capacitance per distance unit:
Calculation example:
110 kV overhead line 150 mm
R'
1
X'
1
C'
Current transformer
Voltage transformer
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 ratio
Setting of the earth to line impedance ratio 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
compensation factor K
237 Format Z0/Z1 (refer to Section 2.1.2.1). Only the addresses applicable for this setting will be displayed.
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
= Current transformer ratio
= Transformation ratio of voltage transformer
2
as above
= 0.19 Ω/km
= 0.42 Ω/km
= 0.008 µF/km
600 A / 1 A
110 kV / 0.1 kV
/R
and the reactance ratio X
E
L
. Which of these two entry options applies, was determined by the setting in address
0
/X
or by entry of the complex earth (residual)
E
L
Functions
2.1 General
59
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