Figure 541: The fault loop impedance model for three-phase impedance measuring
element
R
1
Positive-sequence resistance from measuring point to fault location
X
1
Positive-sequence reactance from measuring point to fault location.
R
F
Physical fault resistance per phase, for example, arc resistance.
The three-phase impedance measuring element measures the physical
fault resistance per phase. The resistive reach setting is common for
three-phase and phase-to-phase impedance measuring elements.
The time delay of operation is defined with the
PP operate delay Znx
(x = 1...
5) setting. The timer can be disabled with the setting
PP Op delay Mod Znx
=
"False". This blocks the OPERATE_Zx (x = 1... 5) output of the three-phase measuring
elements.
Entering the line reach
The line reach is entered in primary ohms. The impedance format is selected
with
Impedance mode Zn
= "Rectangular" for the vectors R, X and "Polar" for the
magnitude and angle.
Impedance mode Zn = Rectangular
In case of phase-to-phase or three-phase impedance measuring elements, the line
reach is defined with:
• Resistive reach:
R1 zone x
(x = 1...5)
• Reactive reach:
X1 zone x
(x = 1...5)
In case of non-directional characteristics, the reactive reach in reverse direction is
defined with the
X1 reverse zone x
(x = 1...5) setting. The characteristic line angle,
denoted as α, is the same for both forward and reverse direction.
1MRS759142 F
Protection functions
REX640
Technical Manual
969
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