ABB RELION REX640, Техническое руководство, Страница: 1198 / 1960

R
1
Estimated positive-sequence resistance from the substation to the fault loca-
tion
X
1
Estimated positive-sequence reactance from the substation to the fault loca-
tion
R
0
Estimated zero-sequence resistance from the substation to the fault location
X
0
Estimated zero-sequence reactance from the substation to the fault location
R
N
Estimated the earth return path resistance (= (R0 – R1)/3) from the substation
to the fault location
X
N
Estimated is the earth return path reactance (= (X0 – X1)/3) from the substa-
tion to the fault
R
fault
Estimated fault resistance at the fault location
The recorded data Flt phase reactance provides the estimated positive-sequence
reactance from the substation to the fault location.
Figure 683: Fault loop impedance for phase-to-earth fault loops “AG Fault”, “BG
Fault” or “CG Fault”
Setting
Flt Loc Det mode is used for selecting between different algorithms for the
calculation of the earth-fault distance. In case of compensated (resonant earthed)
networks where an earth-fault current raising resistor is used, setting
Flt Loc Det
mode = "Comp, switched R" should be selected. In all other cases of system neutral
point earthing (effectively earthed, low-resistance, low-reactance or unearthed
networks), setting "Non-comp" should be selected.
Earth-fault distance calculation in case of non-compensated networks
In case of non-compensated networks (effectively earthed, low-resistance,
lowreactance or unearthed networks), the setting Flt Loc Det mode is equal to
"Noncomp". Furthermore, the earth-fault distance calculation algorithm is selected
with setting EF algorithm Sel. Options for the selection are "Load compensation"
and "Load modelling". For the correct operation of both algorithms, there should
not be any zero-sequence current sources, for example, earthing transformers, in
front of the protection relay.
The “Load compensation” algorithm uses symmetrical components to compensate
for the effect of load on the measured voltages and currents. In case of radial
feeders, this algorithm should be selected with low-impedance/effectively earthed
systems where the fault current is fed from one side only and there are no in-feeds
along the protected line.
The “Load modelling” algorithm takes into account the effect of the load in the
measured currents and voltages by considering it in the fault loop model. In case
Protection related functions 1MRS759142 F
1198 REX640
Technical Manual