Maintenance records are created in a similar manner, with the supervisor task instructing the platform software to
log a r
ecord when it receives a maintenance record message. However, it is possible that a maintenance record
may be triggered by a fatal error in the relay in which case it may not be possible to successfully store a
maintenance record, depending on the nature of the problem.
For more information, see the Monitoring and Control chapter.
5.6 DISTURBANCE RECORDER
The disturbance recorder operates as a separate task from the protection and control task. It can record the
w
aveforms of the calibrated analog channels, plus the values of the digital signals. The recording time is user
selectable up to a maximum of 10.5 seconds. The disturbance recorder is supplied with data by the protection and
control task once per cycle, and collates the received data into the required length disturbance record. The
disturbance records can be extracted using application software or the SCADA system, which can also store the
data in COMTRADE format, allowing the use of other packages to view the recorded data.
For more information, see the Monitoring and Control chapter.
5.7 FUNCTION KEY INTERFACE
The function keys interface directly into the PSL as digital input signals. A change of state is only recognized when
a k
ey press is executed on average for longer than 200 ms. The time to register a change of state depends on
whether the function key press is executed at the start or the end of a protection task cycle, with the additional
hardware and software scan time included. A function key press can provide a latched (toggled mode) or output
on key press only (normal mode) depending on how it is programmed. It can be configured to individual protection
scheme requirements. The latched state signal for each function key is written to non-volatile memory and read
from non-volatile memory during relay power up thus allowing the function key state to be reinstated after power-
up, should power be inadvertently lost.
Chapter 4 - Software Design P24xM
52 P24xM-TM-EN-2.1
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