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6.17.1.2 Software Monitoring
Watchdog
7SJ63 Manual
C53000-G1140-C120-1
current measured from a separate current transformer. If all four currents inputs are
connected, their digitized sum must be zero.
Faults in the current circuit are recognized if
⋅i
) | > Σ , 7+5(6+2/'⋅ I
I
=|i
+i
+i
+(k
F
a
b
c
N
g
(= address &7 1&7 3K) takes into account a possible difference
The factor k
N
in the neutral current transformer ratio. Σ , 7+5(6+2/' and Σ , )$&725 are pro-
grammable settings. The component Σ , )$&725 ⋅ I
able error of the input transformer, which can be especially large when high fault cur-
rent levels are present (Figure 6-61). The dropout ratio is about 97%. This malfunction
is reported as ")DLOXUH Σ,".
Note:
Current sum monitoring is only in effect if the ground current for the line to be protect-
ed is connected.
I
F
I
N
DÃUCS@TCPG9
Σ
Figure 6-61
Current Sum Monitoring
For continuous monitoring of the program sequences, a time monitor is provided in the
hardware (hardware watchdog) that runs upon failure of the processor or an internal
program, and causes a complete restart of the processor system.
An additional software watchdog ensures that malfunctions during the processing of
programs are discovered. This also initiates a restart of the processor system.
To the extent such a malfunction is not cleared by the restart, an additional restart at-
tempt is begun. After three unsuccessful restarts within a 30 second window of time,
the device automatically removes itself from service and the red "Error" LED lights up.
The readiness relay opens and indicates "device malfunction" with its normal contact.
+ Σ , )$&725 ⋅ I
N
max
takes into account the allow-
max
Increase:
DÃA68UPS
Σ
I
max
I
N
Functions
6-149
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