ABB Relion REC615, Техническое руководство

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Flt loop reactance Flt phase reactance X
= =
1
(Equation 54)
Figure 251: 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 252 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 55)
Flt loop resistance R R
fault
= +
1
(Equation 56)
Flt loop reactance Flt phase reactance X
= =
1
(Equation 57)
1MRS758755 C Protection related functions
REC615 & RER615
Technical Manual
503