10.4
SEL-787 Relay Instruction Manual Date Code 20081022
Testing and Troubleshooting
Commissioning Tests
➤ The ac and dc elementary schematics and wiring diagrams for
this relay installation
➤ A continuity tester
➤ A protective relay ac test source
➢ Minimum: single-phase voltage and current with phase
angle control
➢ Preferred: three-phase voltage and current with phase
angle control
Connection Tests
Step 1. Remove control voltage and ac signals from the SEL-787 by
opening the appropriate breaker(s) or removing fuses.
Step 2. Isolate the relay contact assigned to be the TRIP output.
Step 3. Verify correct ac and dc connections by performing point-to-
point continuity checks on the associated circuits.
Step 4. Apply ac or dc control voltage to the relay.
After the relay is energized, the front-panel green ENABLED LED
should illuminate.
Step 5. Use the appropriate serial cable (SEL cable C234A or
equivalent) to connect a PC to the relay.
Step 6. Start the PC terminal emulation software and establish
communication with the relay.
Refer to Section 7: Communications for more information on
serial port communications.
Step 7. Set the correct relay time and date by using either the front-
panel or serial port commands (TIME hh:mm:ss and DATE
mm/dd/yy commands).
Step 8. Using the SET, SET P, SET G, SET L, and SET R serial port
commands, enter the relay settings from the settings sheets for
your application.
Step 9. If you are connecting an external SEL-2600 series RTD
module, follow the substeps below; otherwise continue with the
next step.
a. Connect the fiber-optic cable to the RTD Module fiber-
optic output.
b. Plug the relay end of the fiber-optic cable into the relay
fiber-optic Rx input (Port 2).
Step 10. Verify the relay ac connections.
Step 11. Connect the ac test source current or voltage to the appropriate
relay terminals.
NOTE: Make sure the current
transformer secondary windings are
shorted before they are disconnected
from the relay.
a. Disconnect the current transformer and voltage
transformer (if present) secondaries from the relay prior
to applying test source quantities.
b. If you set the relay to accept phase-to-ground voltages
(DELTA_Y := WYE), set the current and/or voltage
phase angles as shown in Figure 10.2.
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