Functions
6-218 7SA522 Manual
C53000-G1176-C119-2
6.16.1.2 Software–Monitoring
Watchdog For the continuous monitoring of the program execution, a time monitoring is incorpo-
rated in the hardware (hardware watchdog). The watchdog expires and resets the
processor system causing a complete reboot if the processor fails or when a program
loses synchronism.
A further software–watchdog ensures that errors in the program execution are detect-
ed. This watchdog also initiates a reset of the processor.
If a fault is not removed by the restart of the processors, a new restart is attempted.
Following three failed restarts within 30 s the protection takes itself out of service and
the red LED “ERROR” is illuminated. The device ready relay resets and alarms the de-
vice failure state with its normally closed contact.
6.16.1.3 Monitoring of the External Instrument Transformer Circuits
Interruptions or short circuits in the secondary circuits of the current and voltage trans-
formers, as well as incorrect terminations (important during commissioning) are large-
ly recognized by the device and alarmed. To this end, the measured values are cycli-
cally checked in the background as long as no fault detection is present.
Current Symmetry During normal system operation, a certain degree of current symmetry can be as-
sumed. This symmetry is checked in the device by means of a magnitude monitoring.
The smallest phase current is compared with the largest. Non-symmetry is detected
when
|I
min
| / |I
max
|<%$/)$&725,
as long as I
max
/ I
N
> %$/$1&(,/,0,7 / I
N
I
max
is the largest and I
min
is the smallest of the three phase currents. The symmetry
factor %$/)$&725, is a measure of the phase conductor non-symmetry, the
threshold value %$/$1&(,/,0,7 represents the lower limit of the operating range
of this monitoring function (refer to Figure 6-115). Both parameters can be set. The
reset ratio is approx. 97 %.
This failure is alarmed by “)DLO,EDODQFH”.
Figure 6-115 Current symmetry monitoring
I
min
I
N
slope:
I
max
I
N
%$/$1&(,/,0,7
%$/)$&725,
To Next Page
Loading...
Need help?
General
