ABB RELION 620 Series Technical Manual page 847

1MRS757644 F
620 series
Technical Manual
Flt phase reactance X
=
GUID-56EC16DD-7F6A-4DE5-935E-4302196DE21A V3 EN
R Estimated positive-sequence resistance from the substation to the fault location
1
X Estimated positive-sequence reactance from the substation to the fault location
1
R Estimated zero-sequence resistance from the substation to the fault location
0
X Estimated zero-sequence reactance from the substation to the fault location
0
R Estimated the earth return path resistance (= (R0 – R1)/3) from the substation to
N
the fault location
X Estimated is the earth return path reactance (= (X0 – X1)/3) from the substation to
N
the fault
R Estimated fault resistance at the fault location
fault
The recorded data Flt phase reactance provides the estimated positive-sequence
reactance from the substation to the fault location.
GUID-B455F553-4F09-442D-9297-4262002D5D07 V2 EN
Figure 434: Fault loop impedance for phase-to-earth fault loops "AG Fault", "BG
Fault" or "CG Fault"
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 location.
The "Load compensation" algorithm utilizes 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 of
radial feeders, this algorithm can be applied with low-impedance/effectively earthed
systems where the fault current is fed from one side only. The "Load modelling"
algorithm has been especially designed for unearthed systems.
Protection related functions
1
Section 5
(Equation 155)
841