GE Multilin L90 Line Current Differential System 1-191 GETTING STARTED 1.5 USING THE RELAY11.5.7 COMMISSIONINGCommissioning tests are included in the Commissioning chapter.The L90 requires minimal maintenance after it is commissioned into service. Since the L90 is a microprocessor-basedrelay, its characteristics do not change over time. As such, no further functional tests are required.The L90 performs a number of continual self-tests and takes the necessary action in case of any major errors (see theRelay Self-tests section in chapter 7). However, it is recommended that L90 maintenance be scheduled with other systemmaintenance. This maintenance can involve in-service, out-of-service, or unscheduled maintenance.In-service maintenance:1. Visual verification of the analog values integrity, such as voltage and current (in comparison to other devices on thecorresponding system).2. Visual verification of active alarms, relay display messages, and LED indications.3. LED test.4. Visual inspection for any damage, corrosion, dust, or loose wires.5. Event recorder file download with further events analysis.Out-of-service maintenance:1. Check wiring connections for firmness.2. Analog values (currents, voltages, RTDs, analog inputs) injection test and metering accuracy verification. Calibratedtest equipment is required.3. Protection elements setting verification (analog values injection or visual verification of setting file entries against relaysettings schedule).4. Contact inputs and outputs verification. This test can be conducted by direct change of state forcing or as part of thesystem functional testing.5. Visual inspection for any damage, corrosion, or dust.6. Event recorder file download with further events analysis.7. LED Test and pushbutton continuity check.Unscheduled maintenance, such as a disturbance causing system interruption:1. View the event recorder and oscillography or fault report for correct operation of inputs, outputs, and elements.If it is concluded that the relay or one of its modules is of concern, contact GE Multilin for service.
