Chapter 22 - Maintenance and Troubleshooting
The device includes several self-monitoring functions to check the operation of its hardware and software while in
service. If there is a problem with the hardware or software, it should be able to detect and report the problem, and
attempt to resolve the problem by performing a reboot. In this case, the device would be out of service for a short
time, during which the 'Healthy' LED on the front of the device is switched OFF and the watchdog contact at the
rear is ON. If the restart fails to resolve the problem, the unit takes itself permanently out of service; the 'Healthy'
LED stays OFF and watchdog contact stays ON.
If a problem is detected by the self-monitoring functions, the device attempts to store a maintenance record to
allow the nature of the problem to be communicated to the user.
The self-monitoring is implemented in two stages: firstly a thorough diagnostic check which is performed on boot-
up, and secondly a continuous self-checking operation, which checks the operation of the critical functions whilst
it is in service.
If the IED does not appear to power up, use the following to determine whether the fault is in the external wiring,
auxiliary fuse, IED power supply module or IED front panel.
Measure the auxiliary voltage on terminals 1 and 2.
Verify the voltage level and polarity against the rating
label on the front.
Terminal 1 is –dc, 2 is +dc
Check the LEDs and LCD backlight switch on at
power-up. Also check the N/O (normally open)
watchdog contact for closing.
Check the output (nominally 48 V DC)
ERROR MESSAGE OR CODE ON POWER-UP
The IED performs a self-test during power-up. If it detects an error, a message appears on the LCD and the power-
up sequence stops. If the error occurs when the IED application software is running, a maintenance record is
created and the device reboots.
Is an error message or code permanently displayed
during power up?
Record displayed error, and then remove and re-apply
IED auxiliary supply.
If the auxiliary voltage is correct, go to test 2. Otherwise check the wiring
and fuses in the auxiliary supply.
If the LEDs and LCD backlight switch on, or the contact closes and no error
code is displayed, the error is probably on the main processor board in the
If the LEDs and LCD backlight do not switch on and the contact does not
close, go to test 3.
If there is no field voltage, the fault is probably in the IED power supply
If the IED locks up and displays an error code permanently, go to test 2.
If the IED prompts for user input, go to test 4.
If the IED reboots automatically, go to test 5.
Record whether the same error code is displayed when the IED is
rebooted. If no error code is displayed, contact the local service centre
stating the error code and IED information. If the same code is
displayed, go to test 3.