Monitoring Functions; Measurement Supervision; Hardware Monitoring; Software Monitoring - Siemens SIPROTEC 4 7UT6 Series Manual

Functions

2.19 Monitoring Functions

2.19 Monitoring Functions
The device is equipped with extensive monitoring capabilities - concerning both, hardware and software. In
addition, the measured values are also constantly checked for plausibility, so that the current and voltage
transformer circuits are largely integrated into the monitoring. It is also possible to implement trip circuit
supervision. This supervision is possible using appropriate available binary inputs.
2.19.1

Measurement Supervision

2.19.1.1

Hardware Monitoring

The device is monitored by the measurement inputs and the output relays. Monitoring circuits and the
processor check the hardware for malfunctions and abnormal states.
Auxiliary and Reference Voltages
The processor voltage of 5 V is monitored by the hardware, as the processor cannot operate if the voltage
drops below the minimum value. In that case, the device is not operational. When the correct voltage has re-
established the processor system is restarted.
Failure or switch-off of the supply voltage sets the device out of operation; this status is signalled by a "life
contact" (closed or open). Transient dips in supply voltage do not disturb the function of the device (see "Tech-
nical Data").
The processor monitors the offset and the reference voltage of the AD (analogue-to-digital converter). The
protection is blocked in case of inadmissible deviations. Continuous malfunctioning is indicated by the alarm
Error MeasurSys , No 181.
Back-up Battery
The back-up battery guarantees that the internal clock continues to work and that metered values and alarms
are stored if the auxiliary voltage fails. The charge level of the battery is checked regularly. On its under-
shooting a minimum admissible voltage, the indication
Memory Components
The working memory (RAM) is tested during booting of the system. If a malfunction occurs, the starting
sequence is interrupted and an LED blinks. During operation the memories are checked with the help of their
checksum.
For the program memory, the cross-check sum is cyclically generated and compared to a stored reference
program cross-check sum.
For the parameter memory, the cross-check sum is cyclically generated and compared to the cross-check sum
that is refreshed after each prarameterisation change.
change. If a fault occurs, the processor system is restarted.
Sampling Frequency
The sampling frequency and the synchronism between the ADCs (analog-to-digital converters) is continuously
monitored. If deviations cannot be corrected by another synchronisation, the device sets itself out of opera-
tion and the red LED "ERROR" lights up. The readiness relay drops off and signals the malfunction by its "life
contact".
2.19.1.2

Software Monitoring

Watchdog
For the continuous monitoring of the program execution, a time monitoring is incorporated 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.
254
Fail Battery , No. 177 is issued.
C53000-G1176-C230-5, Edition 09.2016
SIPROTEC 4, 7UT6x, Manual