Alstom MiCOM P846, Technical Manual

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Maintenance P846/EN MT/D
MiCOM P846
(MT) 11-3
1. MAINTENANCE
1.1 Maintenance period
It is recommended that products supplied by Alstom Grid receive periodic monitoring after
installation. In view of the critical nature of protective relays and their infrequent operation, it
is desirable to confirm that they are operating correctly at regular intervals.
Alstom Grid protective relays are designed for a life in excess of 20 years.
MiCOM relays are self-supervizing and so require less maintenance than earlier designs of
relay. Most problems will result in an alarm so that remedial action can be taken. However,
some periodic tests should be done to ensure that the relay is functioning correctly and the
external wiring is intact.
1.2 Maintenance checks
Although some functionality checks can be performed from a remote location by utilizing the
communications ability of the relays, these are predominantly restricted to checking that the
relay is measuring the applied currents and voltages accurately, and checking the circuit
breaker maintenance counters. Therefore it is recommended that maintenance checks are
performed locally (i.e. at the substation itself).
Before carrying out any work on the equipment, the user should be familiar with the
contents of the Safety and Technical Data sections and the ratings on the equipment’s
rating label.
1.2.1 Alarms
The alarm status LED should first be checked to identify if any alarm conditions exist. If so,
press the read key [
c
] repeatedly to step through the alarms.
Clear the alarms to extinguish the LED.
1.2.2 Opto-isolators
The opto-isolated inputs can be checked to ensure that the relay responds to their
energization by repeating the commissioning test detailed in section 5.2.6 of the
Commissioning section (P846/EN CM).
1.2.3 Output relays
MT
The output relays can be checked to ensure that they operate by repeating the
commissioning test detailed in section 5.2.7 of the Commissioning section (P846/EN CM).
1.2.4 Measurement accuracy
If the power system is energized, the values measured by the relay can be compared with
known system values to check that they are in the approximate range that is expected. If
they are then the analog/digital conversion and calculations are being performed correctly by
the relay. Suitable test methods can be found in sections 7.1.1 and 7.1.2 of the
Commissioning section (P846/EN CM).
Alternatively, the values measured by the relay can be checked against known values
injected into the relay via the test block, if fitted, or injected directly into the relay terminals.
Suitable test methods can be found in sections 5.2.9 and 5.2.10 of the Commissioning
section (P846/EN CM). These tests will prove the calibration accuracy is being maintained.