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Memory monitoring
Memory is monitored as follows, depending on the type of memory, and checks are done to verify
that memory circuits are healthy:
• Random access memory monitoring:
• Program memory monitoring: Checks the checksum value of the written data.
• Setting value monitoring:
Watchdog Timer
A hardware timer that is cleared periodically by the software is provided, which checks that the
software is running normally.
DC Supply Monitoring
The secondary voltage level of the built-in DC/DC converter is monitored, and is checked to see
that the DC voltage is within a prescribed range.
LCD Panel Connection Monitoring
The connection between LCD panel (HMI module) and SPMM module is monitored.
3.3.3
CT Failure Supervision
This function is available for [APPL-CT] = "3P" setting only.
Figure 3.3.1 shows the scheme logic of the CT failure supervision (CTFS). If the residual
overcurrent element EFF(EFCF) operates and the residual overvoltage element ZOVF(ZOVCF)
does not operate, CT failure (CTF) is detected. When the CTFS detects a CTF, can alarm and
block various protections by PLC function.
The CTF signal is reset 100 ms after the CT failure condition has reset. When the CTF continues
for 10s or more, an alarm signal "CTF alarm" is output.
Further, the CT failure is detected when the binary input signal (external CTF) by PLC function is
received.
This function can be enabled or disabled by the scheme switch [CTFEN] and has a programmable
reset characteristic. For latching operation, set to "ON", and for automatic reset after the recover,
set to "OPT-ON".
300, 1992
EFF
301, 1993
ZOVF
1
&
"ON"
[CTFEN]
≥1
+
"OPT-ON"
CB CLOSE
0.2s
A.M.F. ON
1616
CTF BLOCK
EXT CTF
1620
Writes/reads prescribed data and checks the storage function.
Checks discrepancies between the setting values stored in
duplicate.
&
1
&
&
CB NON BLK
1
1
Figure 3.3.1
⎯
131
≥1
t
0
t
0
0.015s
0.1s
CT Failure Supervision
⎯
6 F 2 S 0 8 4 2
505
≥1
CTF
&
t
0
CTF ALM
10s
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