Signals; Settings - ABB RELION REX640 Technical Manual

Section 4
Protection functions
4.3.4.7
4.3.4.8
Table 608: LREFPNDF Group settings (Basic)
Parameter
Operate value
670
LREFPNDF does not respond to phase-to-phase faults either, as in this case the fault
current flows between the two line CTs and so the neutral CT does not experience this
fault current.
Blocking based on the second harmonic of the neutral current
The transformer magnetizing inrush currents occur when the transformer is energized
after a period of de-energization. The inrush current can be many times the rated
current, and the halving time can be up to several seconds. For the differential
protection relay, the inrush current represents the differential current, which causes
the protection relay to operate almost always when the transformer is connected to the
network. Typically, the inrush current contains a large amount of second harmonics.
The blocking also prevents unwanted operation at the recovery and sympathetic
magnetizing inrushes. At the recovery inrush, the magnetizing current of the
transformer to be protected increases momentarily when the voltage returns to normal
after the clearance of a fault outside the protected area. The sympathetic inrush is
caused by the energization of a transformer running in parallel with the protected
transformer already connected to the network.
Blocking the starting of the restricted earth-fault protection at the magnetizing inrush
is based on the ratio of the second harmonic and the fundamental frequency
amplitudes of the neutral current Io_2H / Io. Typically, the second harmonic content
of the neutral current at the magnetizing inrush is higher than that of the phase
currents.

Signals

Table 606: LREFPNDF Input signals
Name
I3P
IRES
BLOCK
Table 607: LREFPNDF Output signals
Name
OPERATE
START
BLK2H

Settings

Values (Range) Unit
5.0...50.0 %In
Type Default Description
SIGNAL - Three-phase currents
SIGNAL - Residual current
BOOLEAN 0=False Block signal for activating the blocking mode
Type Description
BOOLEAN Operate
BOOLEAN Start
BOOLEAN 2nd harmonic block
Step Default
1.0 5.0
1MRS759142 C
Description
Operate value
Technical Manual
REX640