ABB REL650 series Technical Manual page 109

1MRK 506 335-UUS A
Technical manual
VA
Phase-to-ground
fault in phase A
0
VA
Phase-to-phase
fault in phase A-B
VB
VA
Three-phase
fault
VC
ANSI09000242 V2 EN
Figure 34: Fault loop model
The Z1 in figure 34 represents the positive sequence impedance from the measuring point
to the fault location. The settings RFPGx (where x is 1-5 depending on selected zone) and
RFPPx (where x is 1-5 depending on selected zone) are the eventual fault resistances in the
faulty place.
Regarding the illustration of three-phase fault in figure 34, 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 needs to be set to operate in Non-directional, Forward or Reverse direction
through the setting DirModeZx (where x is 1-5 depending on selected zone). The result
from respective set value is illustrated in figure 35. The impedance reach is not symmetric,
in the sense that it conforms for forward and reverse direction (there are different forward
Z1
IA
IN
KN·Z1
Z1
IA
IB
Z1
Z1
IA
IC
Z1
Section 6
Impedance protection
Phase-to-ground
element
RFPG
(Arc + tower
resistance)
Phase-to-phase
element A-B
RFPP
(Arc resistance)
0.5·RFPP Phase-to-phase
element A-C
0.5·RFPP
ANSI09000242_2_en.vsd
103