ABB RELION Series Technical Manual page 495

1MRS758755 A
REC615 and RER615
Technical Manual
GUID-9CBC31C7-4DF6-4555-9029-4188CCC5533C V2 EN
Figure 252: 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.
Fault loop "ABC Fault"
Fault loop "ABC Fault" is used exclusively for the three-phase short circuit fault.
Figure 253 shows the three-phase fault loop model. The following impedances are
measured and stored in the recorded data of SCEFRFLO.
Flt point resistance R
=
GUID-2503378E-4AC5-4E9F-9D77-2E7C71592C37 V3 EN
Flt loop resistance R
=
1
GUID-F9E2B211-9C30-4A81-ABD4-525CC10AB7A8 V2 EN
Flt loop reactance Flt phase reactance
=
GUID-049B892B-9031-4361-843B-7102E6A4DA17 V3 EN
Protection related functions
fault
R
+
fault
X
=
1
Section 5
(Equation 55)
(Equation 56)
(Equation 57)
489