Areva MiCOM P441, Technical Manual

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Relay Description P44x/EN HW/E33
MiCOM P441/P442 & P444 Page 43/44
5. SELF TESTING & DIAGNOSTICS
The relay includes a number of self-monitoring functions to check the operation of its
hardware and software when it is in service. These are included so that if an error or fault
occurs within the relay’s hardware or software, the relay is able to detect and report the
problem and attempt to resolve it by performing a re-boot. This involves the relay being out
of service for a short period of time which is indicated by the ‘Healthy’ LED on the front of the
relay being extinguished and the watchdog contact at the rear operating. If the restart fails to
resolve the problem, then the relay will take itself permanently out of service. Again this will
be indicated by the LED and watchdog contact.
If a problem is detected by the self-monitoring functions, the relay attempts to store a
maintenance record in battery backed-up SRAM to allow the nature of the problem to be
notified to the user.
The self-monitoring is implemented in two stages: firstly a thorough diagnostic check which
is performed when the relay is booted-up, e.g. at power-on, and secondly a continuous self-
checking operation which checks the operation of the relay’s critical functions whilst it is in
service.
5.1 Start-up self-testing
The self-testing which is carried out when the relay is started takes a few seconds to
complete, during which time the relay’s protection is unavailable. This is signalled by the
‘Healthy’ LED on the front of the relay which will illuminate when the relay has passed all of
the tests and entered operation. If the testing detects a problem, the relay will remain out of
service until it is manually restored to working order.
The operations that are performed at start-up are as follows:
5.1.1 System boot
The integrity of the flash EPROM memory is verified using a checksum before the program
code and data stored in it is copied into SRAM to be used for execution by the processor.
When the copy has been completed the data then held in SRAM is compared to that in the
flash EPROM to ensure that the two are the same and that no errors have occurred in the
transfer of data from flash EPROM to SRAM. The entry point of the software code in SRAM
is then called which is the relay initialisation code.
5.1.2 Initialisation software
The initialisation process includes the operations of initialising the processor registers and
interrupts, starting the watchdog timers (used by the hardware to determine whether the
software is still running), starting the real-time operating system and creating and starting the
supervisor task. In the course of the initialisation process the relay checks:
•
the status of the battery.
•
the integrity of the battery backed-up SRAM that is used to store event, fault and
disturbance records.
•
the voltage level of the field voltage supply which is used to drive the opto-isolated
inputs.
•
the operation of the LCD controller.
•
the watchdog operation.
At the conclusion of the initialisation software the supervisor task begins the process of
starting the platform software.