ABB RELION 620 Series Technical Manual page 850

Section 5
Protection related functions
844
Considered inaccuracies affecting the calculated fault distance estimate are reported
in the recorded result quality indicator value Flt Dist quality in
Fault loops "AB Fault", "BC Fault" or "CA Fault"
Fault loops "AB Fault", "BC Fault" or "CA Fault" are used for phase-to-phase short
circuit faults as well as in the case of a two-phase-to-earth fault if the individual earth
faults are located at the same feeder.
model. The following impedances are measured and stored in the recorded data of
SCEFRFLO.
R
Flt point resistance
=
GUID-F8007C95-5C0B-4FBA-B724-0BC45E64841F V3 EN
Flt loop resistance R
=
1
GUID-CB02F4ED-8E75-4C30-BB25-3F4984D75FC8 V3 EN
Flt loop reactance Flt phase reactance
=
GUID-049B892B-9031-4361-843B-7102E6A4DA17 V3 EN
GUID-9CBC31C7-4DF6-4555-9029-4188CCC5533C V2 EN
Figure 436: 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. The
load compensation should be disabled only if the ratio between the fault current and
load current is large 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 =
"TRUE". However, valid distance estimate, that is, the conversion of measured
impedance (''electrical fault distance'') into a physical fault distance requires
accurate positive sequence impedance settings.
Figure 436
fault
2
R
fault
+
2
X
=
1
1MRS757644 F
Table 811.
shows the phase-to-phase fault loop
Technical Manual
(Equation 158)
(Equation 159)
(Equation 160)
620 series