Monitoring Functions; Measurement Supervision; Hardware Monitoring - Siemens SIPROTEC 4 7VK61 Manual

2.7

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.
2.7.1

Measurement Supervision

2.7.1.1

Hardware Monitoring

The device is monitored from the measuring inputs up to the command relays. Monitoring circuits and the
processor check the hardware for malfunctions and inadmissible conditions.
Auxiliary and Reference Voltages
The processor voltage of 5 V is monitored by the hardware, as the processor no longer functions on under-
shooting the minimum value. In that case, the device is not operational. On recovery of the voltage the
processor system is restarted.
If the supply voltage is removed or switched off, the device is taken out of service, and an indication is imme-
diately generated by a normally closed contact. Brief voltage interruptions of up to 50 ms do not disturb the
operational readiness of the device (see Technical Data).
The processor monitors the reference voltage of the ADC (analog-to-digital converter). The protection is
suspended if the voltages deviate outside an allowable range, and persistent deviations are reported.
Buffer battery
The buffer battery, which ensures the operation of the internal clock and the storage of counters and indica-
tions if the auxiliary voltage fails, is periodically checked for charge status. On its undershooting a minimum
admissible voltage, the indication
If the device is not supplied with auxiliary voltage for more than 1 or 2 days, the internal clock is switched off
automatically, i.e. the time is not registered any more. The data in the event and fault buffers, however,
remain stored.
Memory Components
The main memory (RAM) is tested when the system starts up. If a fault is detected during this process, the
startup is aborted. Error LED and LED 1 light up and the remaining LEDs start flashing simultaneously. During
operation the memory is checked by means of its checksum.
A checksum of the program memory (EPROM) is cyclically generated and compared with the stored program
checksum.
A checksum for the parameter memory (FLASH-EPROM) is cyclically generated and compared with the
checksum which is computed after each change of the stored parameters.
If a malfunction occurs, the processor system is restarted.
Offset of the Analogue-to-Digital Converter
The offset of the ADC is measured cyclically for each channel and corrected. When the offset reaches an inad-
missibly high value, the indication
active.
Sampling frequency
The sampling frequency and the synchronism of the analog-digital converters is continuously monitored. If
any deviations cannot be removed by remedied synchronization, then the processor system is restarted.
SIPROTEC 4, 7VK61, Manual
C53000-G1176-C159-5, Edition 05.2018
Fail Battery (no.177) is issued.
Error Offset (No. 191) is displayed. The protection functions remain
Functions
2.7 Monitoring Functions
131