The inherent result from the fault distance calculation is the ohmic fault loop
impedance value.
Table 1150: The calculated impedance values available in the recorded data
Impedance valule Description
Flt phase reactance Estimated positive sequence reactance from the substation to the
fault location in primary ohms.
Flt point resistance Fault resistance value in the fault spot in primary ohms. The compo-
sition of this term depends on the fault loop as described in the
following subsections.
Flt loop resistance
The total fault loop resistance from the substation to the fault loca-
tion in primary ohms. Fault point resistance is included in this value.
The composition of this term is different for short-circuit and earth-
fault loops as described in the following subsections.
Flt loop reactance
The total fault loop reactance from the substation to the fault loca-
tion in primary ohms. The composition of this term is different for
short-circuit and earth-faults loops as described in the following
subsections.
These impedance values can be used as such or they can be further processed in
system-level fault location applications, such as distribution management system
(DMS).
5.7.5.3 Fault loops “AG Fault” or “BG Fault” or “CG Fault”
Fault loops “AG Fault”, “BG Fault” and “CG Fault” are used for single-phase-toearth
faults. When the earth faults are located at different feeders, they are also applied
in the case of two-phase-to-earth faults. In this case, the phase-to-earth loop (“AG
Fault”, “BG Fault” or “CG Fault”) corresponding to the faulty phase at the protected
feeder is used for calculation.
Figure 683
shows the phase-to-earth fault loop
model. The following impedances are measured and stored in the recorded data
of SCEFRFLO.
Flt point resistance R
fault
=
(Equation 293)
Flt loop resistance R R R
N fault
= + +
1
(Equation 294)
Flt loop reactance X X
N
= +
1
(Equation 295)
(Equation 296)
1MRS759142 F
Protection related functions
REX640
Technical Manual
1197
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