1-20 B90 Low Impedance Bus Differential System GE Multilin1.5 USING THE RELAY 1 GETTING STARTED1 1.5.7 COMMISSIONINGThe B90 requires a minimum amount of maintenance when it is commissioned into service. Since the B90 is a micropro-cessor-based relay, its characteristics do not change over time. As such, no further functional tests are required. Expectedservice life is 20 years for UR devices manufactured June 2014 or later when applied in a controlled indoors environmentand electrical conditions within specification.Furthermore, the B90 performs a number of continual self-tests and takes the necessary action in case of any major errors(see the Relay Self-tests section in chapter 7 for details). However, it is recommended that B90 maintenance be scheduledwith other system maintenance. This maintenance may involve the 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 during 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 prompt service.
