Siemens 7SJ82 - Application and Setting Notes

Measured-Value Correction at Load Current on Lines Fed on Both Sides
In the case of faults on lines fed on both sides and with load transport (see next figure), the fault voltage Υ
F1
is
not only influenced by the source voltage Ε
1
, but also by the source voltage Ε
2
, if both voltage sources feed to
the common fault resistance R
F
. Without special measures, this leads to measuring errors in the impedance-
calculation result, since the current component Ι
F2
cannot record at the measuring point M. For long lines and
lines subject to high loads, this measuring error can be considerable in the crucial X component of the fault
impedance (for the distance calculation).
The fault location has a load compensation, which corrects this measuring error in 1-pole short-circuits. A
correction is not possible for the R component of the fault impedance. However, the measuring error is not
critical here, as only the X component is decisive for the fault distance.
The load compensation acts in 1-phase short circuits. In doing so, both the positive-sequence and zero-
sequence system of the balanced components are analyzed for the correction. You can activate and deactivate
the load compensation via the Load compensation parameter.
[dwfailur-190912-01.tif, 1, en_US]
Figure 6-322 Fault Currents and Voltages in a Line Fed on Both Sides
M Measuring point
S1, S2 Source voltage (EMF)
IF1, IF2 Partial fault currents
IF1 + IF2 Total fault current
VF1 Fault voltage at the measuring point
RF Common fault resistance
ZF1, ZF2 Fault impedances
ZF1gnd,
ZF2gnd
Ground fault impedances
ZS1, ZS2 External impedances
ZS1gnd,
ZS2gnd
Ground external impedances
Application and Setting Notes
The function requires the following key line data to calculate fault distance:
•
Reactance per unit length of the line per kilometer or per mile
•
Line length for the correct output of the fault distance as a percentage of the line length
•
The residual compensation factors in setting format Kr and Kx
6.46.4
Protection and Automation Functions
6.46 Fault Locator
SIPROTEC 5, Overcurrent Protection, Manual 935
C53000-G5040-C017-8, Edition 07.2017