ABB COM600 series User's & Technical Manual page 21

1MRS758734 COM600 series 5.1
Substation Analytics Technical Manual
FLT_DISTANCE output is not valid. The estimated impedances are still calculated and
shown normally in their respective outputs.
Fault loop "ABC Fault"
Fault loop "ABC Fault" is used exclusively for the three-phase short circuit fault. Fig-
ure 4.3-19 shows the measured impedances.
Figure 4.3-16 (Equation 12)
Figure 4.3-17 (Equation 13)
Figure 4.3-18 (Equation 14)
Figure 4.3-19 Fault loop impedance for a three-phase fault impedance loop ("ABC Fault")
The three-phase fault distance is calculated with a special measuring element using
positive-sequence quantities. This is advantageous especially in case of nontransposed
(asymmetric) lines, as the influence of line parameter asymmetry is reduced. If the line
is non-transposed, all the phase-to-phase loops have different fault loop reactances. The
use of positive-sequence quantities results in the average value of phase-to-phase loop
reactances, that is, the most representative estimate in case of three-phase faults.
fault_loop_impedance_three_phase_fault_impedance_loop.png
equation_12.png
equation_13.png
equation_14.png
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