ABB RELION REX640, Technical Manual, Page: 1204 / 1960

Flt loop resistance R
R
fault
= +
1
2
(Equation 300)
Flt loop reactance Flt phase reactance X
= =
1
(Equation 301)
Figure 686: Fault loop impedance for phase-to-phase fault loops (either “AB Fault”,
“BC Fault” or “CA Fault”)
The fault distance calculation algorithm for the phase-to-phase fault loops is
defined by using settings
Load Com PP loops and Enable simple model. Options
for the selection are "Disabled" or "Enabled".
Load compensation can be enabled or disabled with setting
Load Com PP loops.
Load compensation should be disabled only if the ratio between the fault current
and load current is high or when the value of the fault distance estimate for the
short circuit fault is required from each shot of an autoreclosing sequence.
The fault distance calculation is most accurate when calculated with the fault loop
model. This model requires positive-sequence impedances of the protected feeder
to be given as settings. If these settings are not available, valid impedance values
can be calculated also without the fault loop model with setting
Enable simple
model = "Enabled". However, a valid distance estimate, that is, the conversion
of measured impedance (“electrical fault distance’’) into a physical fault distance
requires accurate positive-sequence impedance settings.
Fault loop “ABC Fault”
Fault loop “ABC Fault” is used exclusively for the three-phase short circuit fault.
Figure 687
shows the three-phase fault loop model. The following impedances are
measured and stored in the recorded data of SCEFRFLO.
Flt point resistance R
fault
=
(Equation 302)
Flt loop resistance R R
fault
= +
1
(Equation 303)
Flt loop reactance Flt phase reactance X
= =
1
(Equation 304)
Protection related functions 1MRS759142 F
1204 REX640
Technical Manual