ABB Relion 620 Series, Technical Manual

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Impedance valule Description
Flt loop resistance
The total fault loop resistance from the substation to the fault lo-
cation in primary ohms. Fault point resistance is included in this
value. The composition of this term is different for short-circuit and
earth-fault loops as described in the following subsections.
Flt loop reactance
The total fault loop reactance from the substation to the fault loca-
tion in primary ohms. The composition of this term is different for
short-circuit and earth-faults loops as described in the following
subsections.
These impedance values can be utilized as such or they can be further processed in
system level fault location applications, such as distribution management system
(DMS).
Fault loops “AG Fault” or “BG Fault” or “CG Fault”
Fault loops “AG Fault”, “BG Fault” or “CG Fault” are used for single-phase-to-earth
faults. When the individual earth faults are located at different feeders, they are
also applied in the case of two-phase-to-earth fault. In this case, the phase-to-earth
loop (either “AG Fault” or “BG Fault” or “CG Fault”) corresponding to the faulty
phase at the protected feeder, is used for calculation.
Figure 444
shows the phase-
to-earth fault loop model. The following impedances are measured and stored in
the recorded data of SCEFRFLO.
Flt point resistance R
fault
=
(Equation 153)
Flt loop resistance R R R
N fault
= + +
1
(Equation 154)
Flt loop reactance X X
N
= +
1
(Equation 155)
Flt phase reactance X
=
1
(Equation 156)
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
Protection related functions 1MRS757644 H
838 620 series
Technical Manual