ABB COM600 series User's & Technical Manual page 17

1MRS758734 COM600 series 5.1
Substation Analytics Technical Manual
equation_6.png
Figure 4.3-7 (Equation 6)
fault_loop_impedance_for_phase-to-earth_fault_impedance_loops.png
Figure 4.3-8 Fault loop impedance for phase-to-earth fault impedance loops "AG Fault", "BG
Fault" or "CG Fault"
The earth-fault distance calculation algorithm is selected by setting EF algorithm Sel to
either "Load compensation" or "Load modelling". For a correct operation of both the
algorithms, there should not be any zero-sequence current sources, for example, earthling
transformers, in front of the IED location.
"Load compensation" utilizes the symmetrical components to compensate for the effect
of the load on the measured voltages and currents. In case of radial feeders, it 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.
"Load modelling" takes into account the effect of the load in measured currents and
voltages by load modelling. In case of radial feeders, the "Load modelling" algorithm
can be applied with low-impedance/effectively earthed systems where the fault current
is fed from one side only.
The "Load modelling" algorithm requires the Equivalent load Dis setting, that is, an
equivalent load distance, as an additional parameter. The maximum value of the voltage
drop, denoted U (real), appears at the end of the line. The Equivalent load Dis parameter
drop
is the distance at which a single load tap corresponding to the total load of the feeder
would result in a voltage drop equal to U (real). The dashed curve shows the voltage
drop
drop profile in this case.
17