ABB RELION REX640 - Page 523

OPERATE
Harmonics
calculation
BLOCK
START
Current
comparison
Level
detector
t
Timer
t
IRES
Io
I_REF_RES
Blocking
logic
Figure 301: Functional module diagram
Harmonics calculation
This module feeds the measured residual current to the high-pass filter, where the
frequency range is limited to start from two times the fundamental frequency of
the network (for example, in a 50 Hz network the cutoff frequency is 100 Hz), that
is, summing the harmonic components of the network from the second harmonic.
The output of the filter, later referred to as the harmonics current, is fed to the Level
detector and Current comparison modules.
The harmonics current I_HARM_RES is available in the monitored data view. The
value is also sent over horizontal communication to the other protection relays on
the parallel feeders configured in the protection scheme.
1MRS759142 F
Protection functions
REX640
Technical Manual
523