10.5
Date Code 20100129 Instruction Manual SEL-751A Relay
Testing and Troubleshooting
Commissioning Tests
Step 19. Perform any desired protection element tests. Perform only
enough tests to prove that the relay operates as intended;
exhaustive element performance testing is not necessary for
commissioning.
Step 20. Connect the relay for tripping duty.
Step 21. Verify that any settings changed during the tests performed in
Step 18 and Step 19 are changed back to the correct values for
your application.
Step 22. Use the serial port commands in Table 10.1 to clear the relay
data buffers and prepare the relay for operation.
This prevents data generated during commissioning testing
from being confused with operational data collected later.
Step 23. When it is safe to do so, energize the feeder.
Step 24. Verify the following ac quantities by using the front-panel
METER > Fundamental or serial port METER command.
➢ Phase current magnitudes should be nearly equal.
➢ Phase current angles should be balanced, have proper
phase rotation, and have the appropriate phase
relationship to the phase voltages.
Step 25. If your relay is equipped with voltage inputs, check the
following:
➢ Phase voltage magnitudes should be nearly equal.
➢ Phase voltage phase angles should be balanced and
have proper phase rotation.
The SEL-751A is now ready for continuous service.
Functional Tests
Phase Current Measuring Accuracy
Step 1. Connect the current source to the relay, as shown in
Figure 10.3.
Step 2. Using the front-panel
SET/SHOW or the serial port SHO
command, record the CTR and PHROT setting values.
Step 3. Set the phase current angles to apply balanced three-phase
currents in accordance with the PHROT setting. Refer to
Figure 10.1.
Step 4. Set each phase current magnitude equal to the values listed in
Column 1 of Table 10.2. Use the front-panel to view the phase
current values. The relay should display the applied current
magnitude times the CTR setting.
Table 10.1 Serial Port Commands That Clear Relay Data Buffers
Serial Port Command Task Perf o rme d
LDP C Clears Load Profile Data
SER R Resets Sequential Events Record buffer
SUM R Resets Event Report and Summary Command buffers
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