Siemens siprotec SJ62, Руководство пользователя

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2.11 Monitoring Functions
186
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
Scanning Scanning and the synchronization between the internal buffer components are con-
stantly monitored. If any deviations cannot be removed by renewed synchronization,
then the processor system is restarted.
2.11.1.3 Software Monitoring
Watchdog For continuous monitoring of the program sequences, a time monitor is provided in the
hardware (hardware watchdog) that expires upon failure of the processor or an inter-
nal 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.
If such a malfunction is not cleared by the restart, an additional restart attempt 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 readi-
ness relay drops out and indicates „device malfunction“ with its normally closed con-
tact.
Offset Monitoring This monitoring function checks all ring buffer data channels for corrupt offset replica-
tion of the analog/digital transformers and the analog input paths using offset filters.
The eventual offset errors are detected using DC voltage filters and the associated
samples are corrected up to a specific limit. If this limit is exceeded an indication is
issued (191
„Error Offset“
) that is part of the warn group annunciation (annunci-
ation 160). As increased offset values affect the reliability of measurements taken, we
recommend to send the device to the OEM plant for corrective action if this annunci-
ation continuously occurs.
2.11.1.4 Monitoring of the Transformer Circuits
Interruptions or short circuits in the secondary circuits of the current and voltage trans-
formers, as well as faults in the connections (important for commissioning!), are de-
tected and reported by the device. The measured quantities are cyclically checked in
the background for this purpose, as long as no system fault is present.
Measurement Value
Acquisition – Cur-
rents Up to four input currents are measured by the device. If the three phase currents and
the ground fault current from the current transformer star point or a separated ground
current transformer of the line to be protected are connected to the device, their digi-
tised sum must be zero. Faults in the current circuit are recognised if
I
F
= | i
A
+ i
B
+ i
C
+ k
I
· i
N
| >
Σ I THRESHOLD
· I
Nom
+
Σ I FACTOR
· I
max
The factor k
I
takes into account a possible difference in the neutral current transformer
ratio I
N
(e.g. toroidal current transformer see addresses
217
,
218
,
204
and
205
):
Σ
I THRESHOLD
and
Σ
I FACTOR
are programmable settings. The component
Σ
I
FACTOR
·
I
max takes into account the permissible current proportional ratio errors of
the input transformer which are particularly prevalent during large short-circuit cur-
rents (Figure 2-58). The dropout ratio is about 97 %. This malfunction is reported as
„Failure
Σ
I“
.