2.19 Fault Locator
351
7SD5 Manual
C53000-G1176-C169-1
The output range extends from 0% to 195%. Output „197“ means that a negative fault
was detected. Output „199“ describes an overflow, i. e. the calculated value is higher
than the maximum possible value of 195 %.
Note
Where the line is not divided into sections, the distance output in kilometers, miles or
percent is only accurate for homogeneous lines. If the line is composed of line sections
with different reactance per unit length characteristics, e.g. overhead line–cable sec-
tions, the reactance calculated by the fault location function can be subjected to a sep-
arate computation to derive the distance to fault, or different line sections can be set.
Line Sections The line type is determined by the line section settings. If, for instance, the line in-
cludes a cable and an overhead line, two different types must be configured. The
system can distinguish between up to three different line types. When configuring
these line data, please note that DIGSI will only show you two or three different tabs
for setup if you have first configured that number of line sections.
Line Symmetry
(only for Double-
Ended Fault Loca-
tor)
The asymmetry of a line can be taken into account in order to achieve greater accu-
racy of the double-ended fault locator. The asymmetry is estimated on the basis of the
phase arrangement. You must set the central phase. If you do not wish an estimation
of the asymmetry, it can be switched off. The system assumes lines having a high
degree of symmetry with respect to the central phase, in particular a single-level ar-
rangement. Figure 2-141 shows possible phase arrangements.
Figure 2-141 Single-level arrangement with central phase
Parallel Line Mea-
sured Value Cor-
rection (Single-
ended Fault Loca-
tor)
In the case of earth faults on double circuit lines, the measured values obtained for
calculation of the impedance are influenced by the mutual coupling of the earth imped-
ance of both parallel lines. This causes measuring errors in the result of the imped-
ance computation unless special measures are taken. The device is therefore provid-
ed with a parallel line compensation function. This function takes the earth current of
the parallel line into consideration when solving the line equation, thereby compensat-
ing for the coupling influence as was the case with the derivation of the distance by
the distance protection (refer to Section 2.5.1 under „Parallel Line Measured Value
Correction“). The earth current of the parallel line must, of course, be connected to the
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