Function Description
Starting Conditions
The fault location is an independent function with its own measurand memory and its own filter algorithms.
To define the valid measuring loop and the most favorable time interval for the measured variable saving, only
a start command is required by the short-circuit protection. The fault location can be started by tripping of the
short-circuit protection or also at each pickup. If another protection device causes the disconnection of a
short-circuit, a fault-location calculation is then also possible for each pickup. In the event of a fault outside
the line to be protected, the fault-location indication cannot always be relevant, however, because the meas-
urands can be falsified by the center infeed for example.
Determining the Fault Location
The recorded sampled values of the short-circuit voltage and voltage are frozen shortly after tripping of the
protection. No error in the measured value has then occurred through the switch-off process, even in the case
of very fast circuit breakers. The measurands and the impedance calculations are automatically filtered and
only indicate a steady-state measured value in the determined data window.
After disconnection of the short-circuit, the measured values are analyzed and the fault location calculated
from the short-circuit loops. If no fault location can be calculated, the indication
FO invalid
is output.
Output of the Fault Location
The following results for the fault location are output:
•
Short-circuit loop determined from the fault reactance
•
Fault reactance X in Ω primary
•
Fault resistance R in Ω primary
•
Fault impedance in polar coordinates (amount in Ω, angle in degrees)
•
Fault distance d of the line proportional to the reactance in kilometers or miles, converted on the basis of
the parameterized reactance per unit length of the line
•
Fault distance d as a percentage of the line length, calculated on the basis of the parameterized reac-
tance per unit length and the parameterized line length
•
Selected fault loop for calculation of the fault location
NOTE
Specification of distance in kilometers, miles, or percent is relevant only for homogenous line sections. If
the line comprises parts which exhibit different reactances per unit of length (for example, overhead-line-
cable sections), you can then analyze the reactance determined from the fault location for separate calcula-
tion of the fault distance.
Measured-Value Correction for Parallel Lines
In the event of ground faults on double lines, the values determined for the impedance calculation are influ-
enced by the coupling of the ground impedances of both line systems. Without special measures, this leads to
measuring errors in the impedance-calculation result. The device is therefore equipped with parallel-line
compensation. This parallel-line compensation takes into account the ground current of the parallel line in the
line equation and consequently compensates the coupling influence, similar to determining of the distance in
distance protection. The ground current of the parallel line must be connected to the device and configured
for this. The parallel-line compensation applies only to faults on the line to be protected. Compensation is not
possible for faults located externally including those on the parallel line.
You can activate and deactivate the parallel-line compensation with the Parallel-line compensat.
parameter.
6.46.3
Protection and Automation Functions
6.46 Fault Locator
934 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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