ABB RELION 670 Series Technical Manual page 193

1MRK 502 066-UUS B
Phase-to-ground
fault in phase A
Phase-to-phase
fault in phase A-B
Three-phase
ANSI05000181 V2 EN-US
Figure 74: Fault loop model
The R1 and jX1 in figure
to the fault location. The settings
place.
Regarding the illustration of three-phase fault in figure 74, 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
OperationDir . The result from respective set value is illustrated in figure 75. The impedance
setting
reach is symmetric, in the sense that it conforms for forward and reverse direction (there are
different forward and reverse settings - Zx and ZxRev respectively, where x = 1 - 5). Therefore, all
reach settings apply to both directions.
Technical manual
Ip
VA
0
IN
IA
VA
IB
VB
IA
VA
fault
IC
VC
74 represents the positive sequence impedance from the measuring point
R1 + j X1
RFPG
(Arc + tower
resistance)
(R0-R1)/3 +
j (X0-X1)/3 )
R1 + j X1
RFPP
(Arc resistance)
R1 + j X1
R1 + j X1
0.5·RFPP
R1 + j X1 0.5·RFPP
RFPG and RFPP are the eventual fault resistances in the faulty
Impedance protection
Phase-to-ground
element
Phase-to-phase
element A-B
Phase-to-phase
element A-C
ANSI05000181_2_en.vsd
Section 7
187