2 MAINTENANCE
2.1 MAINTENANCE CHECKS
In view of the critical nature of the application, Alstom Grid products should be checked at regular intervals to
confirm they are operating correctly. Alstom Grid 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 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 SFTY/4LM and the ratings on
the equipment’s rating label.
2.1.1 ALARMS
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.
2.1.2 OPTO-ISOLATORS
Check the opto-inputs by repeating the commissioning test detailed in the Commissioning chapter.
2.1.3 OUTPUT RELAYS
Check the output relays by repeating the commissioning test detailed in the Commissioning chapter.
2.1.4 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 device's terminals. Suitable test methods can be found in the
Commissioning chapter. These tests will prove the calibration accuracy is being maintained.
Chapter 15 - Maintenance and Troubleshooting MiCOM P747
370 P747-TM-EN-1
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