12 Maintenance and Troubleshooting
2 MAINTENANCE
2.1 Maintenance checks
In view of the critical nature of the application, General Electric products should be checked at regular
intervals to confirm they are operating correctly.
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 substation.
Caution: Before carrying out any work on the equipment you should be familiar with the
contents of the Safety Section or the Safety Guide Pxxx-SG-4LM-3 and the
ratings on the equipment’s rating label.
2.1.1 Opto-Isolators
Check the opto-inputs by repeating the commissioning test detailed in the Commissioning chapter.
2.1.2 Output Relays
Check the output relays by repeating the commissioning test detailed in the Commissioning chapter.
2.1.3 Measurement Accuracy
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 IED's terminals. These tests will prove the
calibration accuracy is being maintained.
2.2 Changing the Battery
The P153 relay has a battery to maintain status data and the correct time when the auxiliary supply
voltage fails.
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