ABB RELION REX640 Technical Manual page 1399

1MRS759142 F
7.4.5 Operation principle
The
the function is enabled and respectively "Off" means function is disabled.
The operation of RCFD can be described by using a module diagram (see Figure
Figure 794
Figure 794: Functional module diagram
7.4.5.1 SCF monitoring
The SCF(Self Clearing Fault) monitoring module provides measurement channel
specific monitoring for phase and residual currents. Following table lists the
options for monitoring and available monitored data values.
Table 1333: SCF monitoring options and data values
Measurement
channel
Phase A current
(I_A)
Phase B current
(I_B)
Phase C current
(I_C)
Residual current
(Io)
Half cycle DFT values are calculated for the SCF detection. Values are available
in monitored data. If the calculated phase current (or residual current) exceeds
above set
REX640
Technical Manual
Operation setting is used to enable or disable the function. When selected "On"
below). All the modules in the diagram are explained in the next sections.
I3P
IRES
BLOCK
Calculated ½
cycle
DFT current
I_CLC_AMPL_A
I_CLC_AMPL_B
I_CLC_AMPL_C
I_CLC_AMPL_N
Phase start value (or Residual start value ), then the corresponding start
I_A
I_B
SCF
I_C
monitoring
Io
Start detection SCF indication
STR_DET_A SLFCLR_FLT_A
STR_DET_B SLFCLR_FLT_B
STR_DET_C SLFCLR_FLT_C
STR_DET_N SLFCLR_FLT_N
Condition monitoring functions
ALARM
SCF counter
SLFCLR_CNT_A
SLFCLR_CNT_B
SLFCLR_CNT_C
SLFCLR_CNT_N
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