ABB RELION Series - Fault Impedance and Distance Calculation

Table 512: Fault types and corresponding fault loops
Fault type Description Flt loop
- No fault No fault
A-E Phase A-to-earth fault AG Fault
B-E Phase B-to-earth fault BG Fault
C-E Phase C-to-earth fault CG Fault
A-B Phase A-to-B short circuit fault AB Fault
B-C Phase B-to-C short circuit fault BC Fault
C-A Phase C-to-A short circuit fault AC Fault
A-B-C-(E) Three-phase short circuit ABC Fault
In case of two-phase-to-earth faults (A-B-E, B-C-E or C-A-E), the selected fault loop
depends on the location of the individual earth faults. When the faults are located at the
same feeder, the corresponding phase-to-phase loop (either “AB Fault” or “BC Fault”
or “CA Fault”) is used for calculation. When the faults are located at different feeders,
the phase-to-earth loop (either “AG Fault” or “BG Fault” or “CG Fault”)
corresponding to the faulty phase at the protected feeder is used for calculation.
5.4.4.2 Fault impedance and distance calculation
As soon as a fault condition is recognized by the phase selection logic, the fault
distance calculation is started with one of the seven impedance-measuring elements,
that is, the fault loops. SCEFRFLO employs independent algorithms for each fault
type to achieve optimal performance.
The inherent result from the fault distance calculation is the ohmic fault loop
impedance value.
Table 513: 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 composition 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 location 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 location 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 utilized as such or they can be further processed in
system level fault location applications, such as distribution management system
(DMS).
Section 5 1MRS758755 A
Protection related functions
484 REC615 and RER615
Technical Manual