ABB RELION REX640 - 7.4.5 Operation principle; 7.4.5.1 SCF monitoring

7.4.5 Operation principle
The Operation setting is used to enable or disable the function. When selected "On"
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 below). All the modules in the diagram are explained in the next sections.
BLOCK
SCF
monitoring
ALARM
I3P
I_A
I_B
I_C
IRES
Io
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
Calculated ½
cycle
DFT current
Start detection SCF indication SCF counter
Phase A current
(I_A)
I_CLC_AMPL_A STR_DET_A SLFCLR_FLT_A SLFCLR_CNT_A
Phase B current
(I_B)
I_CLC_AMPL_B STR_DET_B SLFCLR_FLT_B SLFCLR_CNT_B
Phase C current
(I_C)
I_CLC_AMPL_C STR_DET_C SLFCLR_FLT_C SLFCLR_CNT_C
Residual current
(Io)
I_CLC_AMPL_N STR_DET_N SLFCLR_FLT_N SLFCLR_CNT_N
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 Phase start value (or Residual start value ), then the corresponding start
1MRS759142 F
Condition monitoring functions
REX640
Technical Manual
1399