GE Multilin L90 Line Current Differential System 11-311 COMMISSIONING 11.1 TESTING117. Apply a current of 0.5 pu at a frequency 1 to 3% higher or lower than nominal only to local relay phase A to verify thatfrequency tracking will not affect PFLL when only one relay has a current input and both relays track frequency. Wait200 seconds and verify the following:ACTUAL VALUES Ö STATUS ÖØ CHANNEL TESTS Ö PFLL STATUS: “OK”ACTUAL VALUES ÖØ METERING ÖØ TRACKING FREQUENCY Ö TRACKING FREQUENCY: actual frequency at both relaysFor 3-terminal configuration, the above-indicated tests should be carried out accordingly.11.1.3 CURRENT DIFFERENTIALThe 87L element has adaptive restraint and dual slope characteristics. The pickup slope settings and the breakpoint set-tings determine the element characteristics. The relay displays both local and remote current magnitudes and angles andthe differential current which helps with start-up activities. When a differential condition is detected, the output operandsfrom the element will be asserted along with energization of faceplate event indicators.1. Ensure that relay will not issue any undesired signals to other equipment.2. Ensure that relays are connected to the proper communication media, communications tests have been performedand the CHANNEL and PFLL STATUS displays indicate OK.3. Minimum pickup test with local current only:• Ensure that all 87L setting are properly entered into the relay and connect a test set to the relay to inject currentinto Phase A.• Slowly increase the current until the relay operates and note the pickup value. The theoretical value of operatingcurrent below the breakpoint is given by the following formula, where P is the pickup setting and S1 is the Slope 1setting (in decimal format):(EQ 11.1)• Repeat the above test for different slope and pickup settings, if desired.• Repeat the above tests for Phases B and C.4. Minimum pickup test with local current and simulated remote current (pure internal fault simulation):• Disconnect the local relay from the communications channel.• Loop back the transmit signal to the receive input on the back of the relay.• Wait until the CHANNEL and PFLL status displays indicate OK.• Slowly increase the current until the relay operates and note the pickup value. The theoretical value of operatingcurrent below breakpoint is given by the following formula:(EQ 11.2)where TAP represents the CT Tap setting for the corresponding channel.• Repeat the above test for different slope and pickup settings, if desired.• During the tests, observe the current phasor at ACTUAL VALUES ÖØ METERING Ö 87L DIFF CURRENT Ö LOCAL IA.This phasor should also be seen at ACTUAL VALUES ÖØ METERING Ö 87L DIFF CURRENT ÖØ TERMINAL 1(2) IA alongwith a phasor of twice the magnitude at ACTUAL VALUES ÖØ METERING Ö 87L DIFF CURRENT ÖØ IA DIFF.• Repeat the above tests for Phases B and C.• Restore the communication circuits to normal.Download the UR Test software from the GE Multilin website (http://www.GEindustrial.com/multilin) or contact GEMultilin for information about the UR current differential test program which allows the user to simulate differentoperating conditions for verifying correct responses of the relays during commissioning activities.NOTEI op 2 P21 2S12–-------------------×=I op2P21 TAP+( )2 2S12 1 TAP 2+( )–--------------------------------------------------------------------------=NOTE
