VA
R1 + j X1
Ip
RFPG
Phase-to-ground
fault in phase A
Phase-to-phase
fault in phase A-B
Three-phase
fault
(Arc + tower
resistance)
0
(R0-R1)/3 +
j (X0-X1)/3 )
IN
VA
R1 + j X1
IA
VB
R1 + j X1
IB
RFPP
VA
R1 + j X1
IA
VC
R1 + j X1
IC
0.5·RFPP
0.5·RFPP
(Arc resistance)
Phase-to-ground
element
Phase-to-phase
element A-B
Phase-to-phase
element A-C
ANSI05000181_2_en.vsd
ANSI05000181 V2 EN
Figure 160: Fault loop model
The R1 and jX1 in figure 77 represents the positive sequence impedance from the
measuring point to the fault location. The settings RFPG and RFPP are the eventual
fault resistances in the faulty place.
Regarding the illustration of three-phase fault in figure
77, there is of course fault
current flowing also in the third phase during a three-phase fault. The illustration
merely reflects the loop measurement, which is made phase-to-phase.
The zone can be set to operate in Non-directional, Forward or Reverse direction
through the setting OperationDir. The result from respective set value is illustrated in
figure
78. The impedance reach is symmetric, in the sense that it conforms for forward
and reverse direction. Therefore, all reach settings apply to both directions.
1MRK505222-UUS C Section 6
Impedance protection
309
Technical reference manual
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