Chapter 22 - Maintenance and Troubleshooting
In view of the critical nature of the application, General Electric products should be checked at regular intervals to
confirm they are operating correctly. General Electric products are designed for a life in excess of 20 years.
The devices are self-supervising and so require less maintenance than earlier designs of protection devices. Most
problems will result in an alarm, indicating that remedial action should be taken. However, some periodic tests
should be carried out to ensure that they are functioning correctly and that the external wiring is intact. It is the
responsibility of the customer to define the interval between maintenance periods. If your organisation has a
Preventative Maintenance Policy, the recommended product checks should be included in the regular program.
Maintenance periods depend on many factors, such as:
The operating environment
The accessibility of the site
The amount of available manpower
The importance of the installation in the power system
The consequences of failure
Although some functionality checks can be performed from a remote location, these are predominantly restricted
to checking that the unit is measuring the applied currents and voltages accurately, and checking the circuit
breaker maintenance counters. For this reason, maintenance checks should also be performed locally at the
Before carrying out any work on the equipment you should be familiar with the
contents of the Safety Section or the Safety Guide SFTY/4LM and the ratings on the
equipment's rating label.
First check the alarm status LED to see if any alarm conditions exist. If so, press the Read key repeatedly to step
through the alarms.
After dealing with any problems, clear the alarms. This will clear the relevant LEDs.
Check the opto-inputs by repeating the commissioning test detailed in the Commissioning chapter.
Check the output relays by repeating the commissioning test detailed in the Commissioning chapter.
If the power system is energised, the measured values can be compared with known system values to check that
they are in the expected range. If they are within a set range, this indicates that the A/D conversion and the
calculations are being performed correctly. Suitable test methods can be found in Commissioning chapter.
Alternatively, the measured values can be checked against known values injected into the device using the test
block, (if fitted) or injected directly into the device's terminals. Suitable test methods can be found in the
Commissioning chapter. These tests will prove the calibration accuracy is being maintained.