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6.7 Maintenance
6.7.1 Regular Testing
The relay is almost completely self-supervised. The circuits which cannot be supervised are binary
input and output circuits and human interfaces.
Therefore regular testing can be minimized to checking the unsupervised circuits. The test
procedures are the same as described in Sections 6.4.1, 6.4.2 and 6.4.3.
6.7.2 Failure Tracing and Repair
Failures will be detected by automatic supervision or regular testing.
When a failure is detected by supervision, a remote alarm is issued with the binary output signal of
FAIL and the failure is indicated on the front panel with LED indicators or LCD display. It is also
recorded in the event record.
Failures detected by supervision are traced by checking the "Auto-supervision "screen on the
LCD.
If any messages are shown on the LCD, the failed module or failed external circuits can be located
by referring to Table 6.7.1.
This table shows the relationship between messages displayed on the LCD and the estimated
failure location. Locations marked with (1) have a higher probability than locations marked with
(2).
As shown in the table, some of the messages cannot identify the fault location definitely but
suggest plural possible failure locations. In these cases, the failure location is identified by
replacing the suggested failed modules with spare modules one by one until the "Alarm" LED is
turned off.
The replacement or investigation should be performed first for the module or circuit with higher
probability in the table.
If there is a failure and the LCD is not working such as a screen is frozen or not displayed, the
failure location is either SPM or HMI module.